S-alkylation of methimazole (1) with 1,2-dichloroethane (DCE) into 1,2-bis[(1-methyl-1H-imidazole-2-yl)thio]ethane (2), that we have described recently, opened the question about its formation pathway(s). Results of the synthetic, NMR spectroscopic, crystallographic and computational studies suggest that, under given conditions, 2 is obtained by direct attack of 1 on the chloroethyl derivative 2-[(chloroethyl)thio]-1-methyl-1H-imidazole (3), rather than through the isolated stable thiiranium ion isomer, i.e., 7-methyl-2H, 3H, 7H-imidazothiazol-4-ium chloride , or in analogy with similar reactions, through postulated, but unproven intermediate thiiranium ion 5. Furthermore, in the reaction with 1, 4a prefers isomerization to the N-chloroethyl derivative, 1-chloroethyl-2,3-dihydro-3-methyl-1H-imidazole-2-thione (7), rather than alkylation to 2, while 7 further reacts with 1 to form 3-methyl-1-[(1-methyl-imidazole-2-yl)thioethyl]-1H-imidazole-2-thione . Additionally, during the isomerization of 3, the postulated intermediate thiiranium ion 5 was not detected by chromatographic and spectroscopic methods, nor by trapping with AgBF4. However, trapping resulted in the formation of the silver complex of compound 3, i.e., bis-{2-[(chloroethyl)thio]-1-methyl-1H-imidazole}-silver(I)tetrafluoroborate , which cyclized upon heating at 80 °C to 7-methyl-2H, 3H, 7H-imidazothiazol-4-ium tetrafluoroborate . Finally, we observed thermal isomerization of both 2 and 2,3-dihydro-3-methyl-1-[(1-methyl-1H-imidazole-2-yl)thioethyl]-1H-imidazole-2-thione (8), into 1,2-bisethane (9), which confirmed their structures.Spontaneous  H-imidazole-2-thione (1) is a worldwide used thyrostatic drug [Methimazole  in solution [H-imidazole-2-yl)thio]ethane (2), primarily isolated in the form of dihydrochloride tetrahydrate (2b). Depending on reaction/isolation conditions, the product can be isolated as an anhydrate (2a) or dihydrate (2c)  . Their m2 is considered to be very interesting since it is a potential methimazole-related substance, and as such should not be present in the marketed product.In the context of the pharmaceutical purity profile, 1 to 2, we carried out synthetic, NMR, crystallographic, and computational studies.Therefore, aiming to get better insight into the formation pathways leading from 1 and DCE, as previously reported, gave 1,2-bis[(1-methyl-1H-imidazole-2-yl)thio]ethane dihydrochloride tetrahydrate (2b) in the form of colorless plate-shaped crystals. The melting point and the NMR data were identical to the data reported earlier ethane dihydrochloride (2d). The latter was isolated by column chromatography in the form of pure colorless crystals. As in the previous case, the mother liquor contained 3, which was isolated in the form of a colorless oil.When the reaction of out acid , the pro4a formation was answered when we discovered that the S-chloroethyl derivative 3 quantitatively isomerizes into imidazothiazolium chloride 4a  Å is attributed to a short contact suggesting an electrostatic interaction  Å, C1-N2 of 1.339(3) Å, and S-C1 of 1.725(2) Å in 4a a suggesteraction c. There eraction c. 3, a “sulfur mustard” type compound, and 4a, formed in the same reaction, we proceeded to elucidate the synthetic pathway to 2. The possibilities were: direct nucleophilic attack of 1 on the already formed intermediate 3 (pathway A), nucleophilic attack of 1 on the intermediate 4a (pathway B), or nucleophilic attack of 1 on the thiiranium (episulfonium) ion (5), a reactive (fleeting) intermediate in analogy with similar reactions -1-methyl-1H-imidazole}-silver(I)tetrafluoroborate (6). However, no further change occurred during the following 40 min . No signals attributable to the thiiranium 5 were detected.The procedure was repeated, using DMSO-4a was treated with silver tetrafluoborate in methanol at room temperature. After 1 hour, pure 7-methyl-2H, 3H, 7H-imidazothiazol-4-ium tetrafluoroborate (4b) was obtained tetrafluoroborate (6) was obtained in the form of colorless prism-shaped crystals  ions in 6  are coorH groups c.3 is not in equilibrium with the thiiranium ion 5  thioethyl]-1H-imidazole-2-thione (8) was obtained in a 19.4% yield , by the reaction of 7 with 1  were detected, indicating thermal instability of 4a.Furthermore, according to TLC of the reaction mixture (dichloromethane: methanol: formic acid = 8:1:0.5), no traces of 1, led to the formation of the previously mentioned 7 (7 observed during kinetic decomposition of 3. The low yield of 7 (25.0%) was attributed to the fact that no changes in the chromatogram were observed after 4–10 h of the reaction time, indicating an equilibrium between 4a and 7. Additionally, the attempts to prepare suitable single crystals of 7 for X-ray analysis failed because 7 isomerized back to 4a soon after isolation at room temperature, both in the solid state and in the solution. This corroborates our conclusions drawn from the reaction kinetics data.The reaction performed under the same conditions, but without tioned 7 . Its str8 was additionally confirmed by thermal isomerization at 170 °C for 10 h into the known crystalline 1,2-bisethane (9) ethane dihydrochloride tetrahydrate  Mp.  208 °C. Melting point and other physical constants were in line with the previously reported -1-methyl-1H-imidazole  was isolated in the form of colorless oil. TLC: Rf = 0.76 (dichloroethane:acetone = 8:2), Rf = 0.66 , MS-QTOF: m/z: [M + H]+ 177.0266, C6H9N2SCl. 1H NMR : N-CH3  3.58, S-CH2-  3.33, J = 7.2 Hz, -CH2-Cl  3.81, J = 7.3 Hz, =N-CH=  6.95, J = 1.3 Hz, -N(CH3)-CH=  7.26, J = 1.1 Hz. 13C NMR : N-CH3 33.3, S-CH2-35.7, -CH2-Cl 43.7, =N-CH= 129.1, -N(CH3)-CH= 123.9, C(S) 139.6.Mother liquor was concentrated 3, by evaporation of the leftover fraction, unreacted, TLC pure, methimazole  was recovered. Mp.  145 °C  and formic acid  were dissolved in 1,2-dichloroethane (10 mL) and refluxed for 17 h. The mixture was evaporated in vacuo, diluted with water (10 mL), neutralized with 1 M NaOH, and extracted three times with dichloromethane. Organic layer was dried over anhydrous sodium sulfate, evaporated under reduced pressure, and purified by column chromatography using silica gel (mesh size 0.063–0.2) and dichloromethane:acetone = 8:2 as eluent yielding 2-[(chloroethyl)thio]-1-methyl-1H-imidazole  in the form of colorless oil and 1,2-bis[(1-methyl-1H-imidazole-2-yl)thio] ethane in the form of a white crystalline solid . Obtained NMR and MS data are in line with those reported previously in the literature for 2a thiazol-4-ium chloride  and 1,2-bis[(1-methyl-1H-imidazole-2-yl)thio]ethane dihydrochloride . It was further subjected to fractionation by column chromatography using silica gel (mesh size 0.063–0.2) and dichloromethane:acetone = 8:2 as eluent, yielding 1,2-bis[(1-methyl-1H-imidazole-2-yl)thio]ethane dihydrochloride  in the form of pure colorless solid. Melting point : 217 °C, TLC: Rf = 0.60 , MS-QTOF: [M + H-2HCl]+ 255.0743, [M-2HCl] 254.066, C10H14N4S2. 1H NMR : N-CH3  3.82, S-CH2-  3.26, N-CH=  7.46, J = 1.8 Hz, -N(CH3)-CH=  7.50, J = 2.2 Hz. 13C NMR : N-CH3 34.6, S-CH2- 34.0, N-CH= 120.5, -N(CH3)-CH= 125.1 C(S) 138.0. Purity (HPLC): 98%, RRT: 20.518.Methimazole  comprised of the crude product was not isolated. 1H NMR : N-CH3  3.62, S-CH2-  4.13, J = 7.7 Hz, N-CH2  4.43, J = 7.7 Hz, N-CH=  7.31, J = 2.2 Hz, -N(CH3)-CH=  7.2, J = 2.2 Hz. 13C NMR : N-CH3 35.2, S-CH2- 48.6, N-CH2 37.1, N-CH= 118.6, -N(CH3)-CH= 126.2 C(S) 150.4. NMR spectra in D2O were in line with spectra of 4a sample obtained by isomerization of 3, but taken in DMSO-6d (see below).7-Methyl-2in vacuo, and the crude residue was purified using column chromatography on silica gel (mesh size 0.063–0.2) and dichloromethane:acetone = 8:2 as eluent, yielding pure 2-[(chloroethyl)thio]-1-methyl-1H-imidazole  in the form of a colorless oil. Obtained NMR data were in line with what was previously reported in the text.Mother liquor that remained after suction of the crude solid product was concentrated H-imidazole  was held for 21 days at 25 °C/60%RH. Formed crystalline product was triturated with cold dichloromethane, collected using vacuum suction, rinsed a few times with cold dichloromethane, and dried, yielding 7-methyl-2H, 3H, 7H-imidazothiazol-4-ium chloride (4a) in the form of needle like crystals . Melting point : 241 °C, TLC: Rf = 0.49 (dichloromethane: methanol: formic acid = 8:1:0.5), ESI MS-QTOF: [M-Cl]+ 141.0485, C6H9N2SCl. 1H NMR : N-CH3  3.72, S-CH2-  4.16–4.26, N-CH2  4.50, J = 7.9 Hz, N-CH=  7.73, J = 2.0 Hz, -N(CH3)-CH=  7.62, J = 1.8 Hz. 13C NMR : N-CH3 36.3, S-CH2- 39.0, N-CH2 49.5, N-CH= 120.2, -N(CH3)-CH= 127.6 C(S) 151.1. Ionic chromatography experimentally determined the percentage of Cl ions (19%) that corresponded to the theoretical value (20%) within the experimental error. The structure of 4a was confirmed by single crystal X-ray diffraction analysis (Method (A) 2-[(Chloroethyl)thio]-1-methyl-1analysis .H-imidazole-2-thione  was purified prior to analysis by column chromatography using silica gel (mesh size 0.063–0.2) and dichloromethane:acetone = 8:2 as eluent. The pure sample was dissolved at room temperature in DMSO-6d (600 µL) after 8 h and subjected to NMR analysis. According to the obtained spectra, the sample consists of 49.0% 7 and 51.0% 4a (yield expressed in molar percentages), which indicates fast isomerization. After 18 h, only peaks of 4a were present in the spectra, confirming complete isomerization of 7 to 4a.Method (B) 1-(Chloroethyl)-3-methyl-1H, 3H, 7H-imidazothiazol-4-ium chloride  was dissolved in methanol (10 mL), and under stirring  silver tetrafluoroborate was added in portions and stirred at the room temperature for 60 min. Colloidal precipitate was filtered through 0.2 µm PTFE filter and filtrate evaporated in vacuo to dryness yielding 7-methyl-2H, 3H, 7H-imidazothiazol-4-ium tetrafluoroborate  in the form of colorless needle-like crystals. Melting point : 135 °C, TLC: Rf = 0.55 (dichloromethane: methanol: formic acid= 8:1:0.5) EI-MS-QQQ: [M]+140.9. 1H NMR : N-CH3  3.70, S-CH2-  4.20, N-CH2  4.47, N-CH=  7.68 J = 2.2 Hz, -N(CH3)-CH=  7.56, J = 1.8 Hz. 13C NMR : N-CH3 35.8, S-CH2- 38.4, N-CH2 49.0, N-CH= 119.7, -N(CH3)-CH= 127.1, C(S) 150.4. The structure of 4b was confirmed by single crystal X-ray diffraction analysis (Method (A) 7-Methyl-2analysis .H-imidazole  was purified prior to analysis by column chromatography using silica gel (mesh size 0.063–0.2) and dichloromethane:acetone = 8:2 as eluent. Pure sample was dissolved at room temperature in DMSO-6d (600 µL) and to that solution silver tetrafluoroborate  was added and the solution heated at 80 °C for 7 h. According to the obtained spectra, the sample consists of 98.0% of 7 (yield expressed in molar percentage). NMR data were in line with the data for 4b reported previously under method A.Method (B) 2-[(Chloroethyl)thio]-1-methyl-1H-imidazole  was dissolved in methanol (7 mL) and to that solution silver tetrafluoroborate  was added in portions under nitrogen and stirring at room temperature, and stirred for an additional 4 h at room temperature (22 °C). The reaction mixture was left overnight at room temperature; the precipitated product was collected using vacuum suction and rinsed a few times with cold 1,2-dichloroethane (15 mL), yielding colorless prism-shaped crystals of bis-{2-[(chloroethyl)thio]-1-methyl-1H-imidazole}-silver(I)tetrafluoroborate . Mp. : 133 °C. 1H NMR : N-CH3  3.79, S-CH2-  3.35, CH2-Cl  3.75, N-CH=  7.57, -N(CH3)-CH=  7.19. The structure of 6 was confirmed by single X-ray diffraction analysis (2-[(Chloroethyl)thio]-1-methyl-1analysis .H-imidazole  and methimazole  were dissolved in acetonitrile (7 mL), and formic acid  was added under stirring, and refluxed for 43 h. The mixture was evaporated in vacuo, diluted with water (7 mL), neutralized with 1 M NaOH, and extracted three times with dichloromethane. Organic layer was dried over anhydrous sodium sulfate, evaporated under reduced pressure, and purified by column chromatography using silica gel (mesh size 0.063–0.2) and dichloromethane:acetone = 8:2 as eluent yielding 1,2-bis[(1-methyl-1H-imidazole-2-yl)thio]ethane in the form of white crystalline solid  and unreacted 2-[(chloroethyl)thio]-1-methyl-1H-imidazole . The obtained NMR and MS data are in line with the previously reported data for 2a [3 in the text.2-[(Chloroethyl)thio]-1-methyl-1H, 3H, 7H-imidazothiazolinium chloride  was dissolved in acetonitrile (10 mL) and heated under reflux. No changes in the chromatogram were observed after 5 h of heating, hence indicating the formation of an equilibrium between 4a and the product. The mixture was heated in total for 10 h, diluted with water (10 mL), and brine extracted with dichloromethane. The organic layer was dried under anhydrous sodium sulfate, evaporated under reduced pressure yielding TLC pure 1-chloroethyl-2,3-dihydro-3-methyl-1H-imidazole-2-thione  in the form of colorless crystals. Melting point : 65 °C. TLC: Rf = 0.97 (dichloromethane: acetone= 8: 2). EI-MS-QQQ: [M + H]+ 177,6. 1H NMR : N-CH3  3.47, CH2-Cl  3.96, J = 6.1, N-CH2  4.27, J = 5.9 Hz, =CH-N-CH3  7.16, J = 2.6 Hz, CH2-N-CH=  7.20, J = 2.2 Hz,. 13C NMR : N-CH3 34.3, CH2-Cl 41.7, N-CH2 48.4, =CH-N-CH3 118.2, CH2-N-CH= 118.0, C(S) 161.9.7-Methyl-2H, 3H, 7H-imidazothiazol-4-ium chloride  and methimazole  in acetonitrile (10 mL) was refluxed for 10 h. The mixture was evaporated under reduced pressure to dryness, the residue dissolved in water (10 mL), neutralized with 1 M NaOH, and extracted with dichloromethane. The organic layer was dried under anhydrous sodium sulphate, concentrated to dryness, and the residue purified by column chromatography on silica gel (mesh size 0.063–0.2) using dichloromethane:acetone = 8:2 as eluent. After evaporation of the selected fraction under reduced pressure, TLC pure 2,3-dihydro-3-methyl-1-[(1-methyl-1H-imidazole-2-yl)thioethyl]-1H-imidazole-2-thione  was obtained in the form of white crystalline product. The reason for the low yield is the formation of an equilibrium between 4a and 7, and consequently only approx. 20–25% of 7 can react with 1. Melting point : 101.7 °C, TLC: Rf = 0.23 (dichloromethane: acetone= 8:2), Rf = 0.61 (dichloromethane: methanol: formic acid= 8:1:0.5), EI-MS-QQQ: m/z [M + H]+ 255.0, 1H NMR : N-(CH3)-C-S-  3.58, S-CH2-  3.31, J = 6.6 Hz, C(S)-N-CH3  3.46, N-CH2  4.15, J = 6.6 Hz, N-(CH3)-CH=  7.11, J = 2.2 Hz, CH-N-CH2  7.17, J = 2.2 Hz, CH-N=  6.97, J = 1.1 Hz, CH-N-CH3  7.27, J = 1.5 Hz. 13C NMR : C(S)-N-CH3 34.3, S-CH2 31.7, N-(CH3)-C-S- 32.9, N-CH2 46.1, N-(CH3)-CH= 118.1, CH-N-CH2 117.7, CH-N= 128.6, CH-N-(CH3)-C-S- 123.5, C-S-CH2- 138.1, C(S)161.4. The structure was confirmed by single crystal X-ray diffraction analysis (Method (A): A solution of 7-methyl-2analysis .H-imidazole-2-thione  with 1  was refluxed in MeCN for 8 h. The mixture was evaporated under reduced pressure to dryness, the residue dissolved in water (10 mL), neutralized with 1 M NaOH, and extracted with dichloromethane. The organic layer was dried under anhydrous sodium sulphate, concentrated to dryness, and the residue purified by column chromatography on silica gel (mesh size 0.063–0.2) using dichloromethane: acetone = 8:2 as eluent. After evaporation of the selected fraction under reduced pressure, TLC pure 2,3-dihydro-3-methyl-1-[(1-methyl-1H-imidazole-2-yl)thioethyl]-1H-imidazole-2-thione  was obtained in the form of white crystalline product. Obtained melting point, Rf value, and NMR data are in line with the data reported previously in the text for 8.Method (B): 1-Chloroethyl-2,3-dihydro-3-methyl-1H-imidazole-2-yl)thio]ethane  was heated in sand bath at the temperature of 170 °C for 17 h. The melt was dissolved in a mixture of dichloromethane: acetone= 8:2 and fractioned by column chromatography on silica gel (mesh size 0.063–0.2) using dichloromethane: acetone 8:2 as eluent. After evaporation of the selected fraction under reduced pressure, TLC pure red crystalline 1,2-Bisethane  was obtained. Melting point : 195 °C (Lit.: mp. 194–195 °C) -1H-imidazole-2-thione  was heated in a sand bath at 170 °C for 10 h. The melt was dissolved in the mixture of dichloromethane:acetone = 8:2 and fractioned by column chromatography on silica gel (mesh size 0.063–0.2) using dichlormethane: acetone = 8:2 as eluent. After evaporation of the selected fraction under reduced pressure, TLC pure red crystalline 1,2-Bisethane  was obtained. The obtained melting point, Rf value, and NMR data are in line with the data reported previously in the text for 9.Method (B): 2,3-Dihydro-3-methyl-1-[ was dissolved in DMSO-6d (600 µL) to the final concentration of 0.3 M and the course of the reaction was monitored by 1H NMR spectroscopy over the period of 3 months at 25 °C. Comparison of the first proton spectrum taken immediately after dilution and ones taken after 3 days showed no differences. Spectra were taken periodically to the almost complete (99.1%) conversion of 3 to the 4a. A minor quantity of 7 was also detected (approx. 0.94%). The obtained NMR data for 4a and 7 are in line with the data reported previously in the text. The proton spectra were processed and the rate constants calculated using Dynamics Center 2.6.3 software.2-[(Chloroethyl)thio]-1-methyl-1H-imidazole  was dissolved in toluene-8d (600 μL), the solution cooled down to −20 °C, and the proton NMR spectrum of the solution was recorded at the same temperature, showing the signals of 3 accompanied by solvent signals. Then, silver tetrafluoroborate  was added and a series of consecutive proton NMR spectra were recorded for a total duration of 3 h while the temperature was gradually increased from −20 °C to 25 °C. Immediately after the addition of the salt, a white precipitate appeared and in all proton spectra no peaks belonging to the starting three were noticed, indicating that the formed precipitate is not soluble in toluene-8d. After no new signals appeared in a period of 3 h and the temperature reached 25 °C, DMSO-6d (600 μL) was added, the precipitate dissolved, and some new peaks appeared.2-[(Chloroethyl)thio]-1-methyl-1H-imidazole  was dissolved in DMSO-6d (600 μL) at 25 °C and the proton NMR spectrum of the solution was recorded showing the signals of 3. After the addition of silver tetrafluoroborate , the recorded 1H spectrum at the same temperature showed the signals belonging to Ag-complex 6. No other signals were noticed. After that, the temperature was increased up to 80 °C and the NMR spectra were consecutively recorded for a total duration of 7 h. After 1 h at 80 °C, the recorded proton spectrum exhibited low intensity signals belonging to tetrafluoroborate salt 4b in addition to the resonance lines of 6. Four hours at 80 °C later, the signals of 6 completely disappeared while signals of 4b dominated. Transformation from 3 to 4b was expected as the equimolar quantities of 3 and silver tetrafluoroborate were used, and the performed experiment clearly confirmed transformation of 3 via 6 to 4b (2-[(Chloroethyl)thio]-1-methyl-1 6 to 4b .4a by spontaneous isomerization of 3 followed by crystallization, 4b and 6 by slow evaporation from methanol, and 8 by slow evaporation from water.Single crystals were obtained by the following methods: 4a, 4b, 6, and 8, were determined by single-crystal X-ray diffraction at the following temperatures: 293 K for 4a, 170 K for 4b, 6 and 8 (4a) and on a Rigaku Oxford Diffraction XtaLAB Synergy-S diffractometer . Program package CrysAlisPro [F2 values against all reflections included anisotropic displacement parameters for all non-H atoms. The positions of H-atoms riding on carbon atoms were determined on stereochemical grounds. The anion moiety in 4b was modelled using various restraints . The SHELX programs operated within the Olex2 crystallographic suite. Geometrical calculations and molecular graphics were done with MERCURY [deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk.The crystal and molecular structures of  6 and 8 . Single-sAlisPro  was usedsAlisPro  and SHELsAlisPro  programs MERCURY . SupplemAll molecular geometries were optimized with a very efficient M06–2X/6–31+G(d) model, which was designed to provide highly accurate thermodynamic and kinetic parameters for various organic systems. To account for the solvent effects, during geometry optimization, the implicit SMD solvation model corresponding to pure DMSO was included. Thermal corrections were extracted from the corresponding frequency calculations, so that all of the presented results correspond to differences in the Gibbs free energies at room temperature and normal pressure. The choice of such computational setup was prompted by its success in reproducing various features of different organic ,27, orga1) with 1,2-dichloroethane to 2 under mild conditions proceeds by the direct attack of 1 at the chloroethyl derivative 3. Although the isomerization of 3 into the stable thiiranium isomer 4a was observed (1 to 2 conversion does not follow that pathway, nor does it go through the thiiranium ion 5, postulated in analogy to similar reactions reported in literature.We established that spontaneous transformation of methimazole (observed , the 1 t4a in reaction with 1 prefers isomerization to the N-chloroethyl derivative 7, rather than alkylation to 2. The 7 further reacts with 1 and forms dimeric thione 8 in low yield. The structures of both 2 and 8 were confirmed by their thermal isomerization to 9. The intermediate thiiranium ion 5 was not detected by chromatographic and spectroscopic methods, nor caught by trapping it with AgBF4. However, during the trapping reaction, the silver complex of 3, i.e., 6, was isolated. When heated to 80 °C, 6 cyclized into the tetrafluoroborate salt 4b.The imidazothiazolium salt 2 is formed by direct reaction of 3 with 1, rather than through the postulated, but unlikely, thiiranium ion 5 or via the stable imidazotiazolium salt 4a.Conclusions from the computational studies, are in agreement with our experimental results, showed that the bis-derivative 1 to 2 conversion, a “sulfur mustard” type compound 3 is also created, which is a further warning that the use of 1,2-dichloroethane should be avoided when working with methimazole.Caution is needed when handling methimazole, due to its high reactivity in 1,2-dichoroethane solution, even under mild conditions, and we discussed this previously. Our current results additionally revealed that in the


Their structures were elucidated by extensive physicochemical and spectroscopic analysis, as well as ECD calculation, modified Mosher’s method and X-ray diffraction crystallography. Compounds 6 and 7 exhibited inhibitory activities on nitric oxide (NO) production induced by lipopolysaccharide in RAW264.7 cells with IC50 values of 24.9 ± 1.7 and 36.4 ± 2.9 μM.Seven undescribed cembranoids, sacraoxides A–G ( Croton, Euphorbia, Macaranga (Euphorbiaceae), Pinus (Pinaceae), Echinodorus (Alismataceae), and Boswellia (Burseraceae), etc , etc .Boswellia trees and has been used as incense and perfumes since antiquity. Olibanum has also been used in traditional medicines for the purpose of relieving pain and removing blood stasis. Cembranoids and triterpenes were reported as the bioactive constituents responsible for these effects  as well as their inhibitory activities against lipopolysaccharide (LPS)-induced NO production in RAW 264.7 mouse monocyte-macrophages.As part of a continuing research for the discovery of bioactive natural products from medicinal plants , a chemi1H and 13C NMR spectra were performed on Bruker AV-600 spectrometer  or a JEOL ECA-500 spectrometer  with the measuring deuterated solvent as the internal reference. The chemical shifts are expressed in δ (ppm) and reported as s (singlet), d (doublet), t (triplet), dd (doublet of doublets), dt (doublet of triplets), ddd (doublet of doublet of doublets), ddt (doublet of doublet of triplets), hept (heptet), br (broad) and m (multiplet), respectively. HRESIMS was conducted using a Waters  ACQUITY SYNAPTTM G2 high-definition mass spectrometer or a Q-Exactive Hybird Quadrupole Qrbitrap mass spectrometer . Single-crystal X-ray diffraction measurements were conducted on a Bruker Smart Apex II diffractometer  with a graphite monochromator. For preparative HPLC, a Waters 515 HPLC pump, equipped with a Shodex RI-101 Differential Refractometer detector and a JASCO UV-970 intelligent UV/VIS detector, was used. RP-HPLC separations were also conducted using an Shimadzu LC-6AD liquid chromatograph with a SPD-20A UV detector equipped with a YMC Pack ODS-A column . Silica gel GF254  was used for TLC. Column chromatography (CC) was performed on Silica gel , Octadecyl silica gel , and Sephadex LH-20 . All reagents were of analytical grade .Optical rotations were measured on a JASCO P-2200 polarimeter  in a 0.5 dm cell. The UV spectra were obtained with a Shimadzu UV 2201 spectrophotometer . The ECD spectra were measured on a JASCO J-1500 spectropolarimeter  in a 10 mm cell. The Boswellia sacra Flueck. syn. Boswellia bhaw-dajiana Birdw. originated in Ethiopia, was furnished by Tianjin Tongrentang Group Co., Ltd. The resin was authenticated by Professor Lin Ma . The voucher specimen (accession number: 11037Q) was deposited in the School of Chinese Materia Medica, Tianjin University of Traditional Chinese Medicine, P. R. China.The gum resin of B. sacra (6.8 kg) was powdered and extracted with 95% EtOH, then the extracts was evaporated to yield a residue (2.5 kg). The residue was separated by silica gel CC, and eluted sequentially with PE (petroleum ether), CH2Cl2 and MeOH. The CH2Cl2 fraction (513 g) was subjected to silica gel CC and eluted with a gradient of PE-EtOAc-MeOH to afford ten fractions (A-I).The gum resin of 2O to afford subfractions B-1 to B-4. Subfraction B-3 (457 mg) was separated by preparative-HPLC with MeOH-H2O (9:1) to afford compound 5 (2.0 mg).Fraction B (12.9 g) was further subjected to an ODS CC, and eluted with a gradient of MeOH-H2O to afford subfraction C-2. Subfraction C-2 (2.1 g) was subjected to Sephadex LH-20 CC and eluted with CH2Cl2-MeOH (1:1) to afford subfractions C-2-1 and C-2–2. Subfraction C-2-2 was separated by preparative-HPLC with MeOH-H2O (9:1) to afford compound 2 (15.4 mg).Fraction C (12.2 g) was subjected to ODS CC, and eluted with a gradient of MeOH-H2O to afford subfractions D-1 to D-7. Subfraction D-3 (651 mg) was separated by preparative-HPLC with MeCN-H2O (7:3) to afford compounds 9 (38.9 mg). Subfraction D-5 (1.2 g) was subjected to Sephadex LH-20 CC and eluted with CH2Cl2-MeOH (1:1), then the subfraction was separated by preparative-HPLC with MeCN-H2O (13:7) to afford compound 6 (4.0 mg). Subfraction D-6 (504 mg) was subjected to Sephadex LH-20 CC and eluted with CH2Cl2-MeOH (1:1), and then the subfraction was separated by preparative-HPLC with MeCN-H2O (7:3) to afford compound 4 (2.7 mg). Subfraction D-7 (336 mg) was separated by preparative-HPLC with MeCN-H2O (7:3) to afford compound 7 (2.5 mg).Fraction D (23.5 g) was subjected to ODS CC and eluted with a gradient of MeOH-H2O (17:3) to afford compound 3 (11.3 mg).Fraction F (18.4 g) was subjected to silica gel CC, and eluted with a gradient of PE-EtOAc to afford subfractions F-1 to F-3. Subfraction F-3 (1.1 g) was subjected to silica gel CC, eluted with PE-Acetone (4:1), and then separated by preparative-HPLC with MeOH-H2O to afford subfractions H-1 and H-2. Subfraction H-2 (1.3 g) was subjected to Sephadex LH-20 CC, eluted with MeOH, and then separated by preparative-HPLC with MeCN-H2O (9:11) to afford compound 8 (9.4 mg).Fraction H (8.3 g) was subjected to ODS CC, and eluted with a gradient of MeOH-H2O to afford subfractions I-1 to I-3. Subfraction I-2 (2.5 g) was subjected to Sephadex LH-20 CC, eluted with CH2Cl2-MeOH (1:1), and then separated by preparative-HPLC with MeOH-H2O (7:3) to afford compound 1 (17.6 mg).Fraction I (10.6 g) was subjected to ODS CC and eluted with a gradient of MeOH-H1), colorless needles; mp 161–162°C [α]25D +15.0 ; UV (MeOH) λmax (log ε) 201 (3.88) nm; ECD  λmax (Δε) 204 (+30.89) nm; IR (film) νmax 3357, 2959, 2921, 1655, 1448, 1383, 1089, 1061, 1033, 1021, 928, 892 cm−1; 1H and 13C NMR spectroscopic data, see m/z 323.2574 [M + H]+ .Sacraoxide A (3), colorless oil [α]25D −4.1 ; UV (MeOH) λmax (log ε) 202 (3.31) nm; ECD  λmax (Δε) 195 (−5.62), 206 (+9.27) nm; IR (film) νmax 3467, 2958, 2928, 1726, 1448, 1372, 1236, 1099, 1027, 925, 890 cm−1; 1H and 13C NMR spectroscopic data, see m/z 387.2513 [M + Na]+ .Sacraoxide B (4), colorless oil [α]25D +10.4 ; UV (MeOH) λmax (log ε) 201 (3.18) nm; ECD  λmax (Δε) 205 (+1.02), 239 (−0.04), 292 (+0.49) nm; IR (film) νmax 3417, 2965, 2932, 2875, 1735, 1732, 1457, 1372, 1310, 1239, 1025, 1023, 923, 886 cm−1; 1H and 13C NMR spectroscopic data, see m/z 323.2581 [M + H]+ ; m/z 345.2401 [M + Na]+ .Sacraoxide C (5), pale yellow oil [α]25D +47.7 ; UV (MeOH) λmax (log ε) 201 (3.09) nm; ECD  λmax (Δε) 207 (+1.48), 237 (−0.00), 295 (+2.00) nm; IR (film) νmax 2965, 2931, 2875, 1732, 1728, 1457, 1372, 1238, 1110, 1023, 918, 886 cm−1; 1H and 13C NMR spectroscopic data, see m/z 387.2515 [M + Na]+ .Sacraoxide D (6), colorless oil [α]25D −64.0 ; UV (MeOH) λmax (log ε) 201 (3.38), 234 (3.08) nm; ECD  λmax (Δε) 203 (+0.60), 241 (−2.01), 280 (+0.02), 348 (−0.72) nm; IR (film) νmax 2960, 2926, 1733, 1684, 1373, 1236, 1240, 1097, 1039, 976, 891 cm−1; 1H and 13C NMR spectroscopic data, see m/z 385.2354 [M + Na]+ .Sacraoxide E (g ε) 201 .38, 234 7), pale yellow oil [α]25D +10.2 ; UV (MeOH) λmax (log ε) 201 (3.50), 226 (3.10) nm; ECD  λmax (Δε) 233 (−2.85), 287 (+0.18) nm; IR (film) νmax 2960, 2929, 1733, 1684, 1374, 1236, 1028, 981, 854 cm−1; 1H and 13C NMR spectroscopic data, see m/z 363.2504 [M + H]+ .Sacraoxide F (g ε) 201 .50, 226 8), white amorphous powder [α]25D +115.0 ; UV (MeOH) λmax (log ε) 201 (3.29) nm; ECD  λmax (Δε) 203 (+22.82) nm; IR (film) νmax 3358, 2919, 2849, 1658, 1632, 1469, 1382, 1075, 977, 944 cm−1; 1H and 13C NMR spectroscopic data, see m/z 305.2583 [M − H2O + H]+ .Sacraoxide G (g ε) 201 .29 nm; E2), colorless oil; 1H NMR  δ 2.41 , 1.91 , 5.11 , 2.15 , 1.94 , 1.83 , 1.62 , 4.72 , 5.57 , 2.93 , 1.69 , 3.20 , 2.07 , 1.74 , 1.80 , 1.83 , 0.97 , 0.88 , 1.62 , 1.74 , 1.16 ; 13C NMR  δ 88.2 (C-1), 30.1 (C-2), 121.2 (C-3), 134.2 (C-4), 34.7 (C-5), 31.3 (C-6), 66.9 (C-7), 138.0 (C-8), 125.6 (C-9), 29.0 (C-10), 78.4 (C-11), 84.3 (C-12), 35.4 (C-13), 30.9 (C-14), 35.8 (C-15), 17.1 (C-16), 18.8 (C-17), 16.4 (C-18), 17.1 (C-19), 20.8 (C-20); HRESIMS m/z 305.2471 [M − H2O + H]+ .Boscartins AD (10), pale yellow oil; 1H NMR  δ 2.42 , 1.89 , 5.22 , 2.15 , 1.98 , 1.82 , 1.68 , 4.68 , 5.18 , 2.90 , 1.88 , 4.72 , 1.78 , 1.64 , 1.86 , 1.81 , 1.82 , 0.88 , 0.96 , 1.65 , 1.68 , 1.18 , 2.09 ; 13C NMR  δ 88.7 (C-1), 30.3 (C-2), 121.1 (C-3), 134.6 (C-4), 34.9 (C-5), 31.3 (C-6), 67.1 (C-7), 138.1 (C-8), 124.1 (C-9), 26.6 (C-10), 78.0 (C-11), 83.3 (C-12), 35.0 (C-13), 30.9 (C-14), 36.0 (C-15), 18.8 (C-16), 17.1 (C-17), 16.1 (C-18), 17.0 (C-19), 21.8 (C-20), 171.1 (C-1′), 21.3 (C-2′); HRESIMS m/z 387.2506 [M + Na]+ .Boscartins L (20H36O4 (M = 340.49 g/mol): monoclinic, space group I2 (no. 5), a = 23.3651 (6) Å, b = 10.1181 (2) Å, c = 67.6869 (15) Å, β = 91.113 (2), V = 15,998.9 (6) Å3, Z = 32, T = 100.01 (11) K, μ(Cu Kα) = 0.608 mm-1, Dcalc = 1.131 g/cm3, 58,130 reflections measured (4.026 ≤ 2θ ≤ 148.16), 25,373 unique  which were used in all calculations. The final R1 was 0.0818 [I > 2σ(I)] and wR2 was 0.2253 .Crystal Data for C2 (2.0 mg) was dissolved in anhydrous pyridine (0.5 ml) and transferred into a dried bottle, and then 10 μL of S-(‒)-α-methoxy-α-(trifluoromethyl) phenylacetyl chloride  was added. After stirring at room temperature for 24 h, the reaction mixture was evaporated to give a residue, which was purified by semipreparative HPLC  to give the R-MTPA ester derivative of 2 . The S-MTPA ester derivative of 2  was obtained by using the same procedure as described above but using R-MTPA-Cl.As described in previous literature , compounR)-MTPA ester of 2 (2a), colorless oil; 1H NMR  δ 2.45 , 1.87 , 5.16 , 1.97 , 1.94 , 1.97 , 1.70 , 5.96 , 5.72 , 3.14 , 1.77 , 3.19 , 2.05 , 1.75 , 1.83 , 1.81 , 1.00 , 0.89 , 1.62 , 1.69 , 1.17 ; HRESIMS m/z 561.2809 [M + Na]+ .(S)-MTPA ester of 2 (2b), colorless oil; 1H NMR  δ: 2.45 , 1.88 , 5.16 , 2.07 , 1.99 , 2.05 , 1.78 , 5.91 , 5.69 , 3.14 , 1.78 , 3.19 , 2.06 , 1.74 , 1.83 , 1.81 , 0.99 , 0.89 , 1.50 , 1.63 , 1.17 ; HRESIMS m/z 561.2804 [M + Na]+ . together with test compounds at various concentrations and then incubated for 24 h. NO production was determined by measuring the accumulation of nitrite in the culture supernatant using Griess reagent. Briefly, 100 μL of the supernatant from incubates were mixed with equal volume of Griess reagent (1% sulfanilamide and 0.1% naphthylene-diamide dihydrochloride in 2.5% H3PO4) and were allowed to stand for 10 min at 37°C in a humidified atmosphere containing 5% CO2. Absorbance at 540 nm was measured using microplate reader. The nitrite concentrations were calculated according to the literature (The RAW 264.7 (ATCCTIB-71) mouse monocyte-macrophages were cultured in RPMI 1640 medium supplemented with penicillin G (100 units/mL), streptomycin (100 mg/ml) and 10% FBS. The cells were seeded in 96-well plastic plates with 1 × 10terature .μL of fresh medium and 10 μL of MTT (5 mg/ml PBS) were added to each well. The cells were incubated at 37°C in a humidified atmosphere containing 5% CO2. After incubating for 4 h, the medium was removed and the violet crystals of formazan in viable cells were dissolved in DMSO. Absorbance at 570 nm was measured using a microplate reader.Cell viability was determined using the mitochondrial respiration-dependent MTT reduction method. After transferring the required supernatant to another plate for the Griess assay, the remaining supernatant was aspirated from the 96-well plates, 100 B. sacra was separated by multiple column chromatography (CC) including silica gel, Sephadex LH-20 and ODS CC, as well as preparative HPLC to afford nine cembranoids  and boscartin L (9) by detailed spectroscopic and physicochemical analyses and comparison of literature data , and their structures were elucidated as follows.A 95% EtOH extract of the gum resin of ids 1–9, . The knoure data . The new1) was isolated as colorless needles (MeOH-H2O) [α]25D +15.0 . The molecular formula of 1 was established as C20H34O3 from a protonated molecule at m/z 323.2574 [M + H]+  in the HRESIMS spectrum. The cembranoid skeleton of 1 was indicated by the characteristic resonances for an isopropyl moiety at δH 1.86 , 0.98  and 0.86  in the 1H NMR spectrum (δC 35.2 (C-15), 16.1 (C-16) and 19.1 (C-17) in the 13C NMR spectrum  and 84.1 (C-12) were assignable to a tetrahydrofuran structure formed by cyclization between C-1 and C-12 through an ether bond, which was indicated by the HMBC correlations between H-15/C-14, H-15/C-1, H3-20/C-12 and H3-20/C-13 (δH 5.27 (H-3), δC 121.9 (C-3), 130.7 (C-4); δH 5.34 (H-9), δC 121.9 (C-9), 140.7 (C-8)] and two oxygenated methines . The assignment of a ∆3,4 olefin moiety in 1 was accomplished by the HMBC correlations between H-3/C-1, H-3/C-18, and H3-18/C-3, while a hydroxy group at C-11 was evident by the HMBC correlations between H-11/C-20 and H3-20/C-11. On the other hand, the ∆8,9 olefin and the second hydroxy group at C-7 were evident by the HMBC correlations between H-11/C-9, H-9/C-11, H3-19/C-9, H3-19/C-7, H-7/C-19, and H-9/C-19. Thus, the planar structure of compound 1 was concluded as 1:12-epoxy-cembra-3,8-dien-7,11-diol.Sacraoxide A ] (1) was unambiguously determined as -1:12-epoxy-cembra-3E,8Z-dien-7,11-diol.The relative configurations were elucidated by interpretation of the NOESY data . The cis0.2 (2)] . Thus, t3) was isolated as colorless oil [α]25D −4.1 . The molecular formula of 3 was established as C22H36O4 from the HRESIMS positive-ion at m/z 387.2513 [M + Na]+ . The 1D and 2D NMR spectroscopic data of 3 were mostly compatible with those of the known compound 2, except for the downfield shifted H-11 resonance (δH 5.13) and the existence of a set of resonances for an acetyl group  ] , 2. The ientated . Meanwhi3, the modified Mosher’s method was carried out (2 was separately esterified with (S) and (R)-MTPA chloride to give corresponding (R) and (S)-MTPA esters, 2a and 2b, respectively. As a result, only mono-substituted (R/S)-MTPA esters were obtained as the products, which were demonstrated by the HRESIMS and NMR spectroscopic data. The fact that OH-7 was esterified, was indicated by the downfield shifted H-7 resonances and the HMBC correlations between H-7/MTPA-C-1′ in 2a and 2b. The regioselectivity was in accordance with cis-relationship between CH3-20 and OH-11 causing steric hindrance effect. The distribution of Δδ values between 2b and 2a indicated the 7R-configuration of 2 (3) was determined as -1:12-epoxy-11-acetoxy-cembra-3E,8Z-dien-7-ol.In order to determine the absolute configurations of compound ried out . Compounion of 2 . Thus, t4) was isolated as colorless oil [α]25D +10.4 . The molecular formula of 4 was established as C20H34O3 from a protonated molecule at m/z 323.2581 [M + H]+  in the HRESIMS spectrum. Compound 4 is a cembranoid possessing a tetrahydrofuran ring and 11-hydroxy group, which was deduced by the same NMR spectroscopic data analysis process as aforementioned in compound 1. However, in the 1H and 13C NMR spectra of 4, the resonances of a methyl doublet at δH 1.04 , and a carbonyl group at δC 213.4 (C-3) were observed  at the B3LYP/6-311++G  level with IEFPCM in MeOH was used to calculate the ECD spectra of two enantiomers of 4. The experimental ECD spectrum of 4 showed a positive cotton effect (CE) at 292 nm (n → π*), a negative CE at 239 nm (π → π*), and a positive CE at 205 nm (n → σ*), which coincided well with the calculated ECD spectrum of -4 (4) was determined as -1:12-epoxy-11-hydroxy-cembra-7E-en-3-one.The absolute configurations of S,12R)-4 , Thus, t5) is an acetylated derivate of compound 4, which was indicated by both HRESIMS and NMR spectroscopic data. The acetoxy group was determined at C-11, since the proton resonance of H-11 (δH 5.13) was observed downfield shifted  was determined as -1:12-epoxy-11-acetoxy-cembra-7E-en-3-one.Sacraoxide D  was isolated as colorless oil [α]25D −64.0 . The molecular formula of 6 was established as C22H34O4 from the HRESIMS positive-ion at m/z 385.2354 [M + Na]+ . Compound 6 is also a cembranoid, with a tetrahydrofuran ring and 11β-acetoxy group, which was suggested by its superimposable resonances in comparison with structurally similar compounds 9, 3, and 5. Other functionalities were suggested to be two trisubstituted olefin groups and a carbonyl moiety. One olefin was assigned to be a trans-∆3,4 moiety by the HMBC correlations between H-3/C-1, H-3/C-18, and H3-18/C-3, as well as the NOESY correlations between H-3/H-5α, and H-2β/H-18  and a carbonyl carbon resonance at δC 201.2 (C-6), which were assigned as 7,8-en-6-one by the 3J-HMBC correlations between H3-19/C-7, H-7/C-5, and H3-18/C-5, as well as the 2J-HMBC correlations between H-5/C-6, and H-7/C-6. The trans-olefinic geometry of ∆7,8 was evident by the NOESY correlation between H-10α/H-7. The experimental ECD spectrum of 6 showed a negative CE at 348 nm (n → π*), a positive CE at 280 nm (π → π*), a negative CE at 241 nm (π → π*), and a positive CE at 203 nm (n → σ*), which coincided well with the calculated ECD spectrum of -6 (6) was determined as -1:12-epoxy-11-acetoxy-cembra-3E,7E-dien-6-one.Sacraoxide E -6 . Thus, t7) has the same molecular formula of C22H34O4 as 6, which was established from a protonated molecule at m/z 363.2504 [M + H]+  in the HRESIMS spectrum. The functionalities of the cembranoid skeleton of compound 7 included a tetrahydrofuran ring and 11β-acetoxy group, as well as two trisubstituted olefin groups and a carbonyl moiety. Detailed analyses of the 2D NMR spectroscopic data assigned the α,β-unsaturated ketone moiety as 7,8-en-9-one by the HMBC correlations between H3-19/C-7, H3-19/C-9, and H-11/C-9 -7 (7) was determined as -1:12-epoxy-11β-acetoxy-cembra-3E,7E-dien-9-one.Sacraoxide F -7 . Thus, t8) was isolated as white amorphous powder [α]25D +115.0 . The molecular formula of 8 was established as C20H34O3 from the HRESIMS positive-ion at m/z 305.2583 [M − H2O + H]+ . Compound 8 is a cembranoid with a tetrahydrofuran ring and OH-11β group, which was suggested by its superimposable resonances in comparison with structurally similar compounds 1, 2 and 4. In comparison to compound 4, the different functionalities of 8 were suggested to be a disubstituted trans-olefin , and an oxygenated quaternary carbon [δC 74.4 (C-4)] -8 (8) was determined as -1:12-epoxy-cembra-2E,7E-dien-4,11-diol.Sacraoxide G (4 (C-4)] , 3. Thei H-2/C-4 . The β-o-18/H-11 . The expS,12R)-8 . Thus, t1–9) were evaluated for their inhibitory activities against lipopolysaccharide (LPS)-induced NO production in RAW 264.7 mouse monocyte-macrophages. Compounds 6 and 7 showed the most potent inhibitory activities with the IC50 values of 36.4 and 24.9 μM respectively, while the others were less active or inactive  plays significant roles in immune and inflammatory responses. The inhibition of NO release may be considered therapeutic in the treatment of inflammatory diseases . Taking inactive . In addiB. sacra resulted in the isolation and structural elucidation of seven undescribed and two known cembranoids. These cembranoids possess a common tertrahydrofuran ring structure through an ether bond between C-1 and C-12. The structures including absolute configurations were determined by extensive physicochemical and spectroscopic analysis, as well as ECD calculation, modified Mosher's method and X-ray diffraction crystallography. Compounds 4, 6, and 7 displayed inhibitory activities against LPS-induced NO production in RAW 264.7 cells with IC50 values ranging from 24.9 to 72.1 μM. These findings will be of particular value for further studies of structurally interesting cembranoids with biological activities from the genus of Boswellia.A phytochemical investigation on the gum resin of


Following publication of the original article , the autThe incorrect authors’ names list is:1, Soudry-Faure Agnès2, Avondo Aurélie1, Roudaut Jean-Baptiste3, Quenot Jean-Pierre3,4,5, Ray Patrick1 and Charles Pierre-Emmanuel3,4*Campanelli FrancescoThe correct authors’ names list is:1, Agnès Soudry-Faure2, Aurélie Avondo1, Jean-Baptiste Roudaut3, Jean-Pierre Quenot3,4,5, Patrick Ray1 and Pierre-Emmanuel Charles3,4*Francesco CampanelliThe author group has been updated above and the original article  has been


N-acylated furazan-3-amine of a Medicines for Malaria Venture (MMV) project has shown activity against different strains of Plasmodium falciparum. Seventeen new derivatives were prepared and tested in vitro for their activities against blood stages of two strains of Plasmodium falciparum. Several structure–activity relationships were revealed. The activity strongly depended on the nature of the acyl moiety. Only benzamides showed promising activity. The substitution pattern of their phenyl ring affected the activity and the cytotoxicity of compounds. In addition, physicochemical parameters were calculated  or determined experimentally (permeability) via a PAMPA. The N--1,2,5-oxadiazol-3-yl)-3-(trifluoromethyl)benzamide possessed good physicochemical properties and showed high antiplasmodial activity against a chloroquine-sensitive strain (IC50(NF54) = 0.019 µM) and even higher antiplasmodial activity against a multiresistant strain (IC50(K1) = 0.007 µM). Compared to the MMV compound, the permeability and the activity against the multiresistant strain were improved.An  Plasmodium. An estimated number of 229 million cases occurred in 2019, resulting in more than 400,000 deaths. The burden of this infection is mostly carried by children under the age of five located in sub-Saharan Africa. Five Plasmodium species are human pathogenic: P. falciparum, P. vivax, P. malariae, P. ovale and P. knowlesi of which P. falciparum is the most predominant cause of death .,29.1, 10elded 15 .26–29 had to be synthesized from methyl 3-(bromomethyl)benzoate and methyl 4-(bromomethyl)benzoate  groups. Aside from a methylene linker, the influence of an ethyl linker was investigated.31, 32, 34 and 35, the amino furazan 9 was treated at first with the corresponding ω-chloroacyl chloride, yielding the ω-chloroalkanamides 30 and 33 . Th. Th1, 101 has the highest ligand efficiency . The compounds 10, 13, 14 and 16 also exhibit promising ligand efficiencies .Ligand efficiency has become an important concept in drug development, partly due to the realization that large ligands have a disadvantage in terms of the molecular properties necessary for bioavailability. It is defined as the binding free energy for a ligand divided by its number of heavy atoms (HA). Proposed acceptable values for drug candidates are ~0.3 kcal/mol/HA and higher. Out of all tested compounds, −1. The structures of all newly synthesized compounds were determined by one- and two-dimensional NMR spectroscopy. NMR spectra: Varian UnityInova 400 (298 K) 5 mm tubes, TMS as internal standard. Shifts in 1H NMR (400 MHz) and 13C NMR (100 MHz) spectra are reported in ppm; 1H- and 13C-resonances were assigned using 1H,1H- and 1H,13C-correlation spectra and are numbered as given in 1H-NMR and 13C-NMR spectra of new compounds are available in Melting points were obtained on an Electrothermal IA 9200 melting point apparatus. IR spectra: Bruker Alpha Platinum ATR FTIR spectrometer (KBr discs); frequencies are reported in cmmethanol (5): NaBH4 (0.57 g (15.00 mmol)) was added in portions to an ice-cooled solution of 3,4-diethoxybenzaldehyde (2.91 g (15.00 mmol)) in dry methanol (16 mL). After that, the ice bath was removed and the reaction mixture was stirred at 25 °C for 1 h. Then, the solvent was evaporated in vacuo and the residue was mixed with water and extracted with CH2Cl2. The combined organic phases were washed with water, dried over anhydrous sodium sulfate and filtered. The solvent was evaporated in vacuo giving compound 5 as colorless oil (2.80 g (95%)), which was used without further purification.NMR data were in accordance with literature data .4-(Chloromethyl)-1,2-diethoxybenzene (6): Thionyl chloride (4.14 g (34.80 mmol)) was added dropwise via a dropping funnel to an ice-cooled solution of benzyl alcohol 5 (2.36 g (12.00 mmol)) in dry CH2Cl2 (50 mL). The ice bath was removed and the reaction mixture was stirred at 25 °C for 20 h. Then, the reaction was quenched with 2N NaOH at 0 °C and the mixture was basified to a pH of 10–11. The aqueous and organic phases were separated and the aqueous phase was extracted with CH2Cl2. The combined organic phases were dried over anhydrous sodium sulfate and filtered and the solvent was removed in vacuo, giving compound 6 as brown oil (2.47 g (96%)), which was used without further purification. IR = 2977, 1604, 1510, 1476, 1428, 1392, 1256, 1232, 1135, 1038, 985, 805; 1H NMR  δ = 1.42–1.47 , 4.06–4.13 , 4.55 , 6.82 , 6.90 , 6.91 ; 13C NMR  δ = 14.76 (2 CH3), 46.71 (CH2Cl), 64.56 (2 CH2), 113.08 (C-5), 113.86 (C-2), 121.21 (C-6), 129.96 (C-1), 148.81 (C-3), 148.93 (C-4); HRMS (EI+) calcd for C11H15ClO2: 214.0761; found: 214.0755.2-acetonitrile (7): Benzyl chloride 6 (2.15 g (10.00 mmol)) was dissolved in dry DMF (20 mL). KCN (1.30 g (20.00 mmol)) was added and the suspension was stirred at 100 °C for 4 h. After that, the solvent was evaporated in vacuo and the residue was mixed with water and extracted with ethyl acetate. The organic phases were combined and washed with water and brine, dried over anhydrous sodium sulfate and filtered. The solvent was evaporated in vacuo, giving compound 7 as brown oil (1.95 g (95%)), which was used without further purification.NMR data were in accordance with literature data .(hydroxyimino)acetonitrile (2): Sodium (0.37 g (12.00 mmol)) was dissolved in dry ethanol (15 mL) and then cooled to 0 °C with an ice bath. A solution of compound 7 (1.64 g (8.00 mmol)) in dry ethanol (10 mL) was added dropwise. Finally, isopentyl nitrite (1.41 g (12.00 mmol)) was added dropwise with a syringe through a septum. The ice bath was removed and the reaction mixture stirred at 25 °C for 20 h. The solution was diluted with ethyl acetate (80 mL) and washed with 2N HCl, 8% aq NaHCO3 and brine. The organic phase was dried over anhydrous sodium sulfate and filtered and the solvent was removed in vacuo, giving compound 2 as white amorphous solid (1.86 g (99%)), which was used without further purification. IR = 3364, 1601, 1512, 1438, 1337, 1273, 1210, 1146, 1076, 1006, 845, 806; 1H NMR  δ = 1.42 , 1.43 , 4.08 , 4.10 , 7.00 , 7.26 , 7.33 ; 13C NMR  δ = 15.16 (CH3), 15.19 (CH3), 65.75 (OCH2), 65.89 (OCH2), 110.68 (C-2), 111.04 (CN), 114.03 (C-5), 121.22 (C-6), 124.25 (C-1), 132.87 (C=NOH), 150.49 (C-3), 152.73 (C-4); HRMS (EI+) calcd for C12H14N2O3: 234.1004; found: 234.0996.2--N’-hydroxy-2-(hydroxyimino)ethanimidamide (8): Oxime 2 (1.41 g (6.00 mmol)) was dissolved in methanol (18 mL) and a solution of NH2OH × HCl (0.50 g (7.20 mmol)) and NaHCO3 (0.61 g (7.20)) in water (9 mL) was added. The mixture was refluxed for 20 h and then the solvent was evaporated in vacuo. The residue was mixed with water (20 mL) and extracted with ethyl acetate. The organic phases were combined dried over anhydrous sodium sulfate and filtered. The solvent was evaporated in vacuo, giving the raw amidoxime which was recrystallized in CH2Cl2 affording compound 8 as beige crystals (0.55 g (34%)). m.p. 148 °C. IR = 3370, 2981, 1661, 1598, 1516, 1444, 1393, 1270, 1201, 1144, 1040, 978, 810; 1H NMR  δ = 1.33 , 3.97–4.07 , 5.67 , 6.95 , 7.06 , 7.22 , 9.39 , 11.34 ; 13C NMR  δ = 14.66 (CH3), 14.72 (CH3), 63.75 (OCH2), 63.81 (OCH2), 110.59 (C-2), 112.59 (C-5), 120.24 (C-6), 127.24 (C-1), 146.64 (C(=NOH)NH2), 147.66 (C-3), 149.20 (C-4), 149.22 (C=NOH); HRMS (EI+) calcd for C12H17N3O4: 267.1219; found: 267.1230.4--1,2,5-oxadiazol-3-amine (9): Amidoxime 8 (0.80 g (3.00 mmol)) was dissolved in 2N NaOH (30 mL) and refluxed for 20 h. The formed precipitate was filtered, washed with water and dried. The beige precipitate was pure product 9 (0.67 g (83%)) and was used without further purification. m.p. 155 °C. IR = 3374, 3322, 3244, 2984, 1593, 1536, 1501, 1396, 1327, 1305, 1253, 1215, 1141, 1111, 1041, 941, 862, 848, 815; 1H NMR  δ = 1.35 , 4.10 , 6.12 , 7.09 , 7.25 , 7.29 ; 13C NMR  δ = 14.62 (CH3), 14.66 (CH3), 63.85 (2 OCH2), 112.20 (C-2’), 113.25 (C-5’), 117.65 (C-1’), 120.60 (C-6’), 146.69 (C-4), 148.35 (C-3’), 149.87 (C-4’), 155.21 (C-3); HRMS (EI+) calcd for C12H15N3O3: 249.1113; found: 249.1099.18, 19, 22 and 23) is as follows: The respective heterocyclic amine (8.00 mmol), K2CO3 (8.00 mmol) and a catalytical amount of NaI (3.20 mmol) were added to a solution of the corresponding benzyl bromide (4.00 mmol) in dry acetonitrile (40 mL). The mixture was refluxed for 20 h. The suspension was cooled and filtered. The filtrate was evaporated in vacuo to dryness. The residue was mixed with water and the aqueous phase was extracted with CH2Cl2. The combined organic phases were washed with 8% aq NaHCO3 and brine. The organic phase was dried over anhydrous sodium sulfate and filtered and the solvent was removed in vacuo, giving pure amines 18, 19, 22 and 23, which were used without further purification.The general procedure for the synthesis of tertiary amines (Methyl 3-((pyrrolidin-1-yl)methyl)benzoate (18): The reaction of methyl 3-(bromomethyl)benzoate (0.92 g (4.00 mmol)), pyrrolidine (0.57 g (8.00 mmol)), K2CO3 (1.11 g (8.00 mmol)) and NaI (0.48 g (3.20 mmol)) in dry acetonitrile (40 mL) gave compound 18 as pale brown oil (0.87 g (99%)).NMR data were in accordance with literature data .Methyl 3-((morpholin-4-yl)methyl)benzoate (19): The reaction of methyl 3-(bromomethyl)benzoate (0.92 g (4.00 mmol)), morpholine (0.70 g (8.00 mmol)), K2CO3 (1.11 g (8.00 mmol)) and NaI (0.48 g (3.20 mmol)) in dry acetonitrile (40 mL) gave compound 19 as yellow oil (0.93 g (99%)).NMR data were in accordance with literature data .Methyl 4-((pyrrolidin-1-yl)methyl)benzoate (22): The reaction of methyl 4-(bromomethyl)benzoate (0.92 g (4.00 mmol)), pyrrolidine (0.57 g (8.00 mmol)), K2CO3 (1.11 g (8.00 mmol)) and NaI (0.48 g (3.20 mmol)) in dry acetonitrile (40 mL) gave compound 22 as pale brown oil (0.82 g (94%)).NMR data were in accordance with literature data .Methyl 4-((morpholin-4-yl)methyl)benzoate (23): The reaction of methyl 4-(bromomethyl)benzoate (0.92 g (4.00 mmol)), morpholine (0.70 g (8.00 mmol)), K2CO3 (1.11 g (8.00 mmol)) and NaI (0.48 g (3.20 mmol)) in dry acetonitrile (40 mL) gave compound 23 as yellow oil (0.90 g (96%)).NMR data were in accordance with literature data .2-(Hydroxyimino)-2-phenylacetonitrile (36): Sodium (0.37 g (12.00 mmol)) was dissolved in dry ethanol (15 mL) and then cooled to 0 °C with an ice bath. A solution of benzyl cyanide (0.94 g (8.00 mmol)) in dry ethanol (10 mL) was added dropwise. Finally, isopentyl nitrite (1.41 g (12.00 mmol)) was added dropwise with a syringe through a septum. The ice bath was removed and the reaction mixture stirred at 25 °C for 20 h. The solution was diluted with ethyl acetate (80 mL) and washed with 2N HCl, 8% aq NaHCO3 and brine. The organic phase was dried over anhydrous sodium sulfate and filtered and the solvent was removed in vacuo, giving compound 36 as yellow amorphous solid (1.15 g (98%)), which was used without further purification.NMR data were in accordance with literature data .N’-Hydroxy-2-(hydroxyimino)-2-phenylethanimidamide (37): Oxime 36 (0.88 g (6.00 mmol)) was dissolved in methanol (18 mL) and a solution of NH2OH × HCl (0.50 g (7.20 mmol)) and NaHCO3 (0.61 g (7.20)) in water (9 mL) was added. The mixture was refluxed for 20 h and then the solvent was evaporated in vacuo. The residue was mixed with water (20 mL) and extracted with ethyl acetate. The organic phases were combined, dried over anhydrous sodium sulfate and filtered. The solvent was evaporated in vacuo, giving the raw amidoxime which was recrystallized in CH2Cl2 affording compound 37 as white crystals (0.25 g (23%)).NMR data were in accordance with literature data .4-Phenyl-1,2,5-oxadiazol-3-amine (38): Amidoxime 37 (0.54 g (3.00 mmol)) was dissolved in 2N NaOH (30 mL) and refluxed for 20 h. The formed precipitate was filtered, washed with water and dried. The white precipitate was pure product 38 (0.17 g (36%)) and was used without further purification.NMR data were in accordance with literature data .20, 21, 24 and 25) is as follows: To a solution of the respective methyl ester (3.00 mmol) in methanol (10 mL), 2N NaOH (9.0 mL) was added. The mixture was stirred at 25 °C for 20 h and then the reaction mixture was acidified with conc HCl to a pH of 6. The solvent was evaporated in vacuo and the residue was mixed with CH2Cl2 (20 mL) and sonicated for 5 min. The suspension was filtered and the filtrate was evaporated in vacuo to dryness, giving pure carboxylic acids 20, 21, 24 and 25, which were used without further purification.The general procedure for the synthesis of carboxylic acids (3-((Pyrrolidin-1-yl)methyl)benzoic acid (20): The reaction of methyl ester 18 (0.66 g (3.00 mmol)) and 2N NaOH (9 mL) in methanol (10 mL) gave compound 20 as white foam (0.17 g (27%)). IR = 2927, 2597, 1613, 1567, 1455, 1381, 1263; 1H NMR  δ = 2.12 2), 3.26 2), 4.20 , 7.40 , 7.55 , 8.07 , 8.50 ; 13C NMR  δ = 23.19 ((CH2)2), 52.71 (N(CH2)2), 58.49 (ArCH2), 128.33 (C-5), 130.39 (C-6), 130.75 (C-1), 132.47 (C-2), 132.55 (C-4), 136.70 (C-3), 170.88 (COOH); HRMS (EI+) calcd for C12H15NO2: 205.1103; found: 205.1088.3-((Morpholin-4-yl)methyl)benzoic acid (21): The reaction of methyl ester 19 (0.71 g (3.00 mmol)) and 2N NaOH (9 mL) in methanol (10 mL) gave compound 21 as white amorphous solid (0.64 g (97%)).NMR data were in accordance with literature data .4-((Pyrrolidin-1-yl)methyl)benzoic acid (24): The reaction of methyl ester 22 (0.66 g (3.00 mmol)) and 2N NaOH (9 mL) in methanol (10 mL) gave compound 24 as white foam (0.55 g (90%)).NMR data were in accordance with literature data .4-((Morpholin-4-yl)methyl)benzoic acid (25): The reaction of methyl ester 23 (0.71 g (3.00 mmol)) and 2N NaOH (9 mL) in methanol (10 mL) gave compound 25 as yellow oil (0.62 g (94%)).NMR data were in accordance with literature data .1, 10–17, 26–29) is detailed in the following subsections.The general procedure for the synthesis of carboxamides (9 (1.00 mmol) and stirred for 20 min. Then, a solution of acid chloride (1.30 mmol) in dry DMF (2 mL) was added dropwise and the reaction mixture was stirred at 60 °C for 20 h. Afterward, the mixture was quenched with water at 0 °C and the aqueous phase was extracted with CH2Cl2. The organic layer was washed with 8% aq NaHCO3 and brine, dried over anhydrous sodium sulfate and filtered, and the solvent was evaporated in vacuo, yielding the raw carboxamides 1 and 10–14, which were further purified by crystallization.An ice-cooled suspension of NaH  in dry DMF (14 mL) was mixed with aminofurazan 2Cl2 (14 mL), oxalyl dichloride 2 M in CH2Cl2 (1.90 mmol) was added dropwise under stirring. After 1 h, the ice bath was removed and the reaction batch was stirred 20 h at 25 °C in an atmosphere of Ar. Subsequently, the solvent was evaporated in vacuo and the crude acyl chloride was dissolved in dry DMF (9 mL). An ice-cooled suspension of NaH  in dry DMF (14 mL) was mixed with aminofurazan 9 (1.00 mmol) and stirred for 20 min. Then, the solution of acyl chloride in dry DMF was added dropwise and the reaction mixture was stirred at 60 °C for 48 h. Afterward, the mixture was quenched with water at 0 °C and the aqueous phase was extracted with CH2Cl2. The organic layer was washed with 8% aq NaHCO3 and brine, dried over anhydrous sodium sulfate and filtered, and the solvent was evaporated in vacuo, yielding the raw carboxamides 16, 17 and 26–29, which were further purified by column chromatography or crystallization.To an ice-cooled solution of carboxylic acid (1.50 mmol) in dry CHN-hydroxysuccinimide (1.58 mmol) and N,N′-dicyclohexylcarbodiimide (1.50 mmol) was dissolved in dry THF (10 mL) and stirred at 25 °C for 20 h. The formed precipitate was filtered and the filtrate was evaporated in vacuo to dryness to obtain the crude NHS ester which was used without further purification. An ice-cooled suspension of NaH  in dry DMF (14 mL) was mixed with aminofurazan 9 (1.00 mmol) and stirred for 20 min. Then, the solution of NHS ester in dry DMF (4 mL) was added dropwise and the reaction mixture was stirred at 60 °C for 20 h. Afterward, the mixture was quenched with water at 0 °C and the aqueous phase was extracted with CH2Cl2. The organic layer was washed with 8% aq NaHCO3 and brine, dried over anhydrous sodium sulfate and filtered, and the solvent was evaporated in vacuo, yielding the raw carboxamide 15, which was further purified by crystallization.A solution of benzoic acid (1.50 mmol), N--1,2,5-oxadiazol-3-yl)-3-methylbenzamide (1): Method A: The reaction of compound 9 (249 mg (1.00 mmol)), 3-methylbenzoyl chloride (201 mg (1.30 mmol)) and NaH  (80 mg (2.00 mmol)) in dry DMF (16 mL) gave the raw carboxamide which was purified by recrystallization in CH2Cl2 to yield compound 1 as white crystals (63 mg (17%)). m.p. 162 °C. IR = 3198, 2981, 1665, 1591, 1531, 1500, 1394, 1377, 1325, 1277, 1260, 1218, 1142, 1042, 940, 862, 810; 1H NMR  δ = 1.20 , 1.32 , 2.40 , 3.90 , 4.05 , 7.07 , 7.32-7.37 , 7.45 , 7.49 , 7.79 , 7.82 , 11.17 ; 13C NMR  δ = 14.47 (CH3), 14.56 (CH3), 20.86 (ArCH3), 63.79 (2 OCH2), 111.68 (C-2”), 113.21 (C-5”), 116.92 (C-1”), 120.44 (C-6”), 125.17 (C-6), 128.52 (C-2), 128.61 (C-5), 132.22 (C-1), 133.41 (C-4), 138.13 (C-3), 148.10 (C-3”), 150.06 (C-3’), 150.33 (C-4”), 151.23 (C-4’), 166.78 (C=O); HRMS (EI+) calcd for C20H21N3O4: 367.1532; found: 367.1526.N--1,2,5-oxadiazol-3-yl)benzamide (10): Method A: The reaction of compound 9 (249 mg (1.00 mmol)), benzoyl chloride (183 mg (1.30 mmol)) and NaH  (80 mg (2.00 mmol)) in dry DMF (16 mL) gave the raw carboxamide which was purified by recrystallization in CH2Cl2 to yield compound 10 as white crystals (81 mg (23%)). m.p. 199 °C. IR = 3212, 2980, 1660, 1591, 1530, 1501, 1468, 1395, 1378, 1324, 1275, 1258, 1216, 1141, 1040, 916, 852, 811; 1H NMR  δ = 1.19 , 1.31 , 3.88 , 4.05 , 7.07 , 7.31 , 7.33 , 7.58 , 7.68 , 8.00 , 11.24 ; 13C NMR  δ = 14.45 (CH3), 14.57 (CH3), 63.78 (2 OCH2), 111.65 (C-2”), 113.19 (C-5”), 116.87 (C-1”), 120.43 (C-6”), 128.05 , 128.74 , 132.10 (C-1), 132.91 (C-4), 148.11 (C-3”), 149.95 (C-3’), 150.36 (C-4”), 151.24 (C-4’), 166.66 (C=O); HRMS (EI+) calcd for C19H19N3O4: 353.1375; found: 353.1373.N--1,2,5-oxadiazol-3-yl)-2-methylbenzamide (11): Method A: The reaction of compound 9 (249 mg (1.00 mmol)), 2-methylbenzoyl chloride (201 mg (1.30 mmol)) and NaH  (80 mg (2.00 mmol)) in dry DMF (16 mL) gave the raw carboxamide which was purified by recrystallization in CH2Cl2 to yield compound 11 as white crystals (103 mg (28%)). m.p. 170 °C. IR = 3214, 2983, 1663, 1591, 1503, 1395, 1377, 1324, 1259, 1216, 1142, 1042, 918, 854, 803, 741, 687, 657, 618; 1H NMR  δ = 1.28 , 1.34 , 2.34 , 3.99 , 4.08 , 7.11 , 7.33–7.37 , 7.45 , 7.65 , 11.12 ; 13C NMR  δ = 14.61 (2 CH3), 19.56 (ArCH3), 63.84 (OCH2), 63.97 (OCH2), 112.06 (C-2”), 113.13 (C-5”), 116.96 (C-1”), 120.67 (C-6”), 125.79 (C-5), 127.89 (C-6), 130.92 (C-4), 131.10 (C-3), 133.97 (C-1), 136.63 (C-2), 148.21 (C-3”), 149.83 (C-3´), 150.34 (C-4”), 151.22 (C-4´), 168.70 (C=O); HRMS (EI+) calcd for C19H21N3O4: 367.1532; found: 367.1526.N--1,2,5-oxadiazol-3-yl)-2-(trifluoromethyl)benzamide (12): Method A: The reaction of compound 9 (249 mg (1.00 mmol)), 2-(trifluoromethyl)benzoyl chloride (271 mg (1.30 mmol)) and NaH  (80 mg (2.00 mmol)) in dry DMF (16 mL) gave the raw carboxamide which was purified by recrystallization in methanol to yield compound 12 as white crystals (38 mg (9%)). m.p. 171 °C. IR = 3209, 2983, 1676, 1604, 1531, 1494, 1397, 1377, 1316, 1277, 1217, 1177, 1129, 1043, 921, 854, 811, 772, 651, 617; 1H NMR  δ = 1.32 , 1.34 , 4.05 , 4.09 , 7.13 , 7.34 , 7.36 , 7.76-7.84 , 7.89 , 11.46 ; 13C NMR  δ = 14.61 (CH3), 14.64 (CH3), 63.84 (OCH2), 63.96 (OCH2), 112.37 (C-2”), 113.09 (C-5”), 116.52 (C-1”), 120.94 (C-6”), 123.52 , 126.25 , 126.71 , 128.69 (C-6), 131.05 (C-4), 132.69 (C-5), 134.03 , 148.23 (C-3”), 149.00 (C-3’), 150.41 (C-4”), 150.72 (C-4’), 166.47 (C=O); HRMS (EI+) calcd for C20H18F3N3O4: 421.1249; found: 421.1248.N--1,2,5-oxadiazol-3-yl)-3-(trifluoromethyl)benzamide (13): Method A: The reaction of compound 9 (249 mg (1.00 mmol)), 3-(trifluoromethyl)benzoyl chloride (271 mg (1.30 mmol)) and NaH  (80 mg (2.00 mmol)) in dry DMF (16 mL) gave the raw carboxamide which was purified by recrystallization in CH2Cl2 to yield compound 13 as white crystals (131 mg (31%)). m.p. 153 °C. IR = 3203, 1675, 1498, 1378, 1336, 1260, 1217, 1172, 1121, 1042, 815; 1H NMR  δ = 1.19 , 1.32 , 3.90 , 4.06 , 7.08 , 7.33 , 7.34 , 7.84 , 8.06 , 8.29 , 8.36 , 11.53 ; 13C NMR  δ = 14.40 (CH3), 14.56 (CH3), 63.77 (OCH2), 63.81 (OCH2), 111.72 (C-2”), 113.24 (C-5”), 116.83 (C-1”), 120.59 (C-6”), 123.82 , 124.66 , 129.33 , 129.44 , 130.18 (C-5), 132.27 (C-6), 133.21 (C-1), 148.11 (C-3”), 149.80 (C-3’), 150.36 (C-4”), 151.08 (C-4’), 165.25 (C=O); HRMS (EI+) calcd for C20H18F3N3O4: 421.1249; found: 421.1242.N--1,2,5-oxadiazol-3-yl)-3-fluorobenzamide (14): Method A: The reaction of compound 9 (249 mg (1.00 mmol)), 3-fluorobenzoyl chloride (206 mg (1.30 mmol)) and NaH  (80 mg (2.00 mmol)) in dry DMF (16 mL) gave the raw carboxamide which was purified by recrystallization in CH2Cl2 to yield compound 14 as beige crystals (186 mg (50%)). m.p. 250 °C. IR = 3216, 2983, 1663, 1591, 1505, 1364, 1275, 1215, 1142, 1039, 880, 857, 809; 1H NMR  δ = 1.27 , 1.33 , 3.99 , 4.07 , 7.06 , 7.32 , 7.48 , 7.63 , 7.81-7.87 , 7.93 ; 13C NMR  δ = 14.60 (CH3), 14.66 (CH3), 63.76 (2 OCH2), 112.34 (C-2”), 113.08 (C-5”), 114.69 , 117.25 , 119.08 (C-1”), 120.60 (C-6”), 124.25 , 129.87 , 140.35 (C-1), 147.84 (C-3”), 149.66 (C-4”), 150.19 (C-4’), 155.35 (C-3’), 161.94 , 166.84 (C=O); HRMS (EI+) calcd for C19H18FN3O4: 371.1261; found: 371.1276.3-Chloro-N--1,2,5-oxadiazol-3-yl)-4-methoxybenzamide (16): Method B: The reaction of 3-chloro-4-methoxybenzoic acid (280 mg (1.50 mmol)) and oxalyl dichloride 2 M in CH2Cl2 (0.95 mL (1.90 mmol)) in dry CH2Cl2 (14 mL) gave the raw acid chloride which was suspended in dry DMF (9 mL) and added to a suspension of compound 9 (249 mg (1.00 mmol)) and NaH  (80 mg (2.00 mmol)) in dry DMF (14 mL), giving the raw carboxamide which was purified by recrystallization in toluene to yield compound 16 as white crystals (255 mg (61%)). m.p. 260 °C (decomp.). IR = 2978, 1663, 1600, 1501, 1470, 1395, 1360, 1271, 1215, 1142, 1057, 1040, 937, 855, 811; 1H NMR  δ = 1.30 , 1.34 , 3.91 , 4.02 , 4.07 , 7.06 , 7.18 , 7.65 , 7.92 , 8.05 , 8.17 , 11.27 ; 13C NMR  δ = 14.69 (2 CH3), 56.27 (OCH3), 63.72 (2 OCH2), 111.80 (C-5), 112.33 (C-2”), 112.99 (C-5”), 119.43 (C-1”), 120.18 (C-3), 120.55 (C-6”), 128.55 (C-6), 129.79 (C-2), 131.72 (C-1), 147.76 (C-3”), 149.48 (C-4”), 150.09 (C-4’), 153.07 (C-3’), 156.03 (C-4), 166.89 (C=O); HRMS (EI+) calcd for C20H20ClN3O5: 417.1092; found: 417.1081.N--1,2,5-oxadiazol-3-yl)-3-fluoro-4-methoxybenzamide (17): Method B: The reaction of 3-fluoro-4-methoxybenzoic acid (255 mg (1.50 mmol)) and oxalyl dichloride 2 M in CH2Cl2 (0.95 mL (1.90 mmol)) in dry CH2Cl2 (14 mL) gave the raw acid chloride which was suspended in dry DMF (9 mL) and added to a suspension of compound 9 (249 mg (1.00 mmol)) and NaH  (80 mg (2.00 mmol)) in dry DMF (14 mL), giving the raw carboxamide which was purified by recrystallization in toluene to yield compound 17 as beige crystals (124 mg (31%)). m.p. 232 °C (decomp.). IR = 3199, 2982, 1663, 1615, 1500, 1469, 1396, 1377, 1327, 1286, 1217, 1140, 1040, 853, 802; 1H NMR  δ = 1.25 , 1.33 , 3.92 , 3.96 , 4.07 , 7.06 , 7.27 , 7.51 , 7.62 , 7.89 , 7.90 , 11.29 ; 13C NMR  δ = 14.55 (CH3), 14.63 (CH3), 56.23 , 63.74 (2 OCH2), 112.02 (C-2”), 113.06 , 115.54 , 118.23 (C-1”), 120.50 (C-6”), 125.30 , 128.22 (C-1), 147.90 (C-3”), 149.86 , 149.89 (C-4”), 150.61 (C-4’), 150.76 , 153.19 (C-3’), 166.11 (C=O); HRMS (EI+) calcd for C20H20FN3O5: 401.1387; found: 401.1380.N--1,2,5-oxadiazol-3-yl)-4-((pyrrolidin-1-yl)methyl)benzamide (26): Method B: The reaction of carboxylic acid 20 (308 mg (1.50 mmol)) and oxalyl dichloride 2 M in CH2Cl2 (0.95 mL (1.90 mmol)) in dry CH2Cl2 (14 mL) gave the raw acid chloride which was suspended in dry DMF (9 mL) and added to a suspension of compound 9 (249 mg (1.00 mmol)) and NaH  (80 mg (2.00 mmol)) in dry DMF (14 mL), giving the raw carboxamide which was purified by recrystallization in toluene to yield compound 26 as light yellow crystals (140 mg (32%)). m.p. 251 °C (decomp.). IR = 2973, 2788, 1584, 1471, 1365, 1271, 1246, 1201, 1141, 1091, 1038, 997, 937, 880, 854, 809; 1H NMR  δ = 1.32 , 1.35 , 1.69 2), 2.43 2), 3.59 , 4.05 , 4.08 , 7.07 , 7.27 , 7.92 , 8.11 , 8.24 ; 13C NMR  δ = 14.74 (CH3), 14.79 (CH3), 23.14 ((CH2)2), 53.54 (N(CH2)2), 59.54 (ArCH2), 63.68 (2 OCH2), 112.67 (C-2”), 112.86 (C-5”), 120.64 (C-1”), 120.72 (C-6”), 127.37 , 128.24 , 139.78 (C-1), 140.34 (C-4), 147.60 (C-3”), 149.12 (C-4”), 149.56 (C-4’), 158.93 (C-3’), 169.56 (C=O); HRMS (EI+) calcd for C24H28N4O4: 436.2111; found: 436.2102.N--1,2,5-oxadiazol-3-yl)-4-((morpholin-4-yl)methyl)benzamide (27): Method B: The reaction of carboxylic acid 25 (332 mg (1.50 mmol)) and oxalyl dichloride 2 M in CH2Cl2 (0.95 mL (1.90 mmol)) in dry CH2Cl2 (14 mL) gave the raw acyl chloride which was suspended in dry DMF (9 mL) and added to a suspension of compound 9 (249 mg (1.00 mmol)) and NaH  (80 mg (2.00 mmol)) in dry DMF (14 mL), giving the raw carboxamide which was purified by recrystallization in toluene to yield compound 27 as pale yellow crystals (258 mg (57%)). m.p. 269 °C (decomp.). IR = 2977, 1585, 1499, 1472, 1360, 1271, 1202, 1141, 1109, 1035, 867; 1H NMR  δ = 1.32 , 1.35 , 2.36 2), 3.49 , 3.58 2), 4.05 , 4.08 , 7.07 , 7.28 , 7.92 , 8.12 , 8.23 ; 13C NMR  δ = 14.75 (CH3), 14.79 (CH3), 53.22 (N(CH2)2), 62.36 (ArCH2), 63.69 (2 OCH2), 66.24 (O(CH2)2), 112.66 (C-2”), 112.86 (C-5”), 120.64 (C-1”), 120.73 (C-6”), 127.86 , 128.28 , 138.60 (C-1), 140.08 (C-4), 147.61 (C-3”), 149.12 (C-4”), 149.56 (C-4’), 158.97 (C-3’), 169.47 (C=O); HRMS (EI+) calcd for C24H28N4O5: 452.2060; found: 452.2043.N--1,2,5-oxadiazol-3-yl)-3-((pyrrolidin-1-yl)methyl)benzamide (28): Method B: The reaction of carboxylic acid 20 (308 mg (1.50 mmol)) and oxalyl dichloride 2 M in CH2Cl2 (0.95 mL (1.90 mmol)) in dry CH2Cl2 (14 mL) gave the raw acid chloride which was suspended in dry DMF (9 mL) and added to a suspension of compound 9 (249 mg (1.00 mmol)) and NaH  (80 mg (2.00 mmol)) in dry DMF (14 mL), giving the raw carboxamide which was purified by column chromatography  to yield compound 28 as yellow oil (262 mg (60%)). IR = 3212, 2974, 2799, 1661, 1591, 1500, 1473, 1395, 1377, 1259, 1217, 1140, 1041, 849, 800; 1H NMR  δ = 1.40 , 1.46 , 1.78–1.81 2), 2.52–2.56 2), 3.69 , 4.04 , 4.11 , 6.91 , 7.23 , 7.25 , 7.42 , 7.57 , 7.75 , 7.87 ; 13C NMR  δ = 14.64 (CH3), 14.65 (CH3), 23.42 ((CH2)2), 54.20 (N(CH2)2), 60.09 (ArCH2), 64.44 (OCH2), 64.58 (OCH2), 112.36 (C-2”), 112.94 (C-5”), 117.28 (C-1”), 120.33 (C-6”), 126.40 (C-6), 127.82 (C-2), 128.92 (C-5), 132.39 (C-1), 133.45 (C-4), 140.34 (C-3), 148.88 (C-3’), 149.08 (C-3”), 149.83 (C-4’), 150.82 (C-4”), 165.69 (C=O); HRMS (EI+) calcd for C24H28N4O4: 436.2111; found: 436.2086.N--1,2,5-oxadiazol-3-yl)-3-((morpholin-4-yl)methyl)benzamide (29): Method B: The reaction of carboxylic acid 21 (332 mg (1.50 mmol)) and oxalyl dichloride 2 M in CH2Cl2 (0.95 mL (1.90 mmol)) in dry CH2Cl2 (14 mL) gave the raw acid chloride which was suspended in dry DMF (9 mL) and added to a suspension of compound 9 (249 mg (1.00 mmol)) and NaH  (80 mg (2.00 mmol)) in dry DMF (14 mL), giving the raw carboxamide which was purified by recrystallization in toluene to yield compound 29 as white crystals (113 mg (25%)). m.p. 199 °C. IR = 2978, 1605, 1502, 1468, 1361, 1271, 1209, 1141, 1114, 1036, 854; 1H NMR  δ = 1.28 , 1.40 , 2.48 2), 3.58 , 3.70 2), 3.94 , 4.09 , 6.98 , 7.36 , 7.43 , 7.64 , 7.72 , 8.00 , 8.03 ; 13C NMR  δ = 15.23 (2 CH3), 54.77 (N(CH2)2), 64.49 (ArCH2), 65.72 (OCH2), 65.76 (OCH2), 67.92 (O(CH2)2), 114.03 (C-2”), 114.47 (C-5”), 121.81 (C-1”), 122.20 (C-6”), 128.81 (C-6), 128.95 (C-5), 131.01 (C-2), 132.31 (C-4), 137.99 (C-3), 140.85 (C-1), 149.92 (C-3”), 151.48 (C-4”), 151.79 (C-4’), 160.84 (C-3’), 173.71 (C=O); HRMS (EI+) calcd for C24H28N4O5: 452.2060; found: 452.2042.N--1,2,5-oxadiazol-3-yl)-3-(trifluoromethoxy)benzamide (15): Method C: The reaction of 3-(trifluoromethoxy)benzoic acid (309 mg (1.50 mmol)), N-hydroxysuccinimide (182 mg (1.58 mmol)) and N,N′-dicyclohexylcarbodiimide (310 mg (1.50 mmol)) in dry THF (10 mL) gave the raw NHS ester. It was suspended in dry DMF (4 mL) and added to a suspension of compound 9 (249 mg (1.00 mmol)) and NaH  (80 mg (2.00 mmol)) in dry DMF (14 mL), giving the raw carboxamide which was purified by recrystallization in CH2Cl2 to yield compound 15 as white crystals (136 mg (31%)). m.p. 145–147 °C. IR = 3209, 1675, 1590, 1501, 1378, 1260, 1216, 1170, 1042, 809, 633; 1H NMR  δ = 1.19 , 1.32 , 3.90 , 4.05 , 7.06 , 7.39–7.44 , 7.63 , 7.68 , 7.96 , 8.06 , 11.32 ; 13C NMR  δ = 14.45, 14.62 (2 CH3), 63.72, 63.78 (2 OCH2), 111.79 (C-2”), 113.13 (C-5”), 117.50 (C-1”), 120.08 , 120.50 (C-2), 120.56 (C-6”), 124.68 (C-4), 127.27 (C-6), 130.75 (C-5), 136.13 (C-1), 148.01 (C-3”), 148.34 (C-3’), 150.14 (C-4”), 150.84 (C-4’), 151.53 (C-3), 165.46 (C=O); HRMS (EI+) calcd for C20H18F3N3O5: 437.1198; found: 437.1171.9 (1.00 mmol) was dissolved in a mixture of dry diethyl ether (4 mL) and dry benzene (16 mL). Dry pyridine (1.13 mmol) was added and then a solution of chloroacyl chloride (1.10 mmol) in dry diethyl ether (4 mL) was added dropwise. The mixture was refluxed for 20 h and then the solvent was evaporated in vacuo. The residue was mixed with water (35 mL) and the aqueous phase was extracted with CH2Cl2. The combined organic layers were dried over anhydrous sodium sulfate and filtered, and the solvent was evaporated in vacuo, yielding the raw carboxamide which was used without further purification. It was dissolved in dry acetonitrile (20 mL), and the respective amine (2.00 mmol), K2CO3 (2.00 mmol) and a catalytical amount of NaI (0.65 mmol) were added. The mixture was stirred at 70 °C for 20 h and then cooled to ambient temperature. The suspension was filtered and the filtrate was evaporated in vacuo to dryness. The residue was mixed with water (20 mL) and the aqueous phase was extracted with CH2Cl2. The organic layer was washed with 8% aqueous NaHCO3 and brine, dried over anhydrous sodium sulfate and filtered, and the solvent was evaporated in vacuo, yielding the carboxamide, which was purified by column chromatography.Amino furazan N--1,2,5-oxadiazol-3-yl)-2-(pyrrolidin-1-yl)acetamide (31): The reaction of amino furazan 9 (249 mg (1.00 mmol)), chloroacetyl chloride (124 mg (1.10 mmol)) and pyridine (89 g (1.13 mmol)) in a mixture of dry diethyl ether (8 mL) and dry benzene (16 mL) gave the raw carboxamide. This was mixed with pyrrolidine (142 mg (2.00 mmol)), K2CO3 (276 mg (2.00 mmol)) and NaI (97 mg (0.65 mmol)) in dry acetonitrile (20 mL), giving the tertiary amine which was purified by column chromatography  to yield compound 31 as pale yellow amorphous solid (87 mg (24%)). IR = 2983, 1726, 1593, 1545, 1519, 1461, 1256, 1216, 1149, 1042, 844, 811; 1H NMR  δ = 1.48 , 1.50 , 1.79–1.85 2), 2.68–2.73 2), 3.38 , 4.13 , 4.17 , 6.97 , 7.12 , 7.22 , 9.73 ; 13C NMR  δ = 14.63 (CH3), 14.70 (CH3), 24.04 ((CH2)2), 54.62 (N(CH2)2), 58.76 (CH2), 64.63, 64.88 (2 OCH2), 113.07 (C-5”), 113.13 (C-2”), 117.07 (C-1”), 120.06 (C-6”), 147.54 (C-3’), 148.36 (C-4’), 149.53 (C-3”), 151.07 (C-4”), 168.87 (C=O); HRMS (EI+) calcd for C18H24N4O4: 360.1797; found: 360.1782.N--1,2,5-oxadiazol-3-yl)-2-(morpholin-4-yl)acetamide (32): The reaction of amino furazan 9 (249 mg (1.00 mmol)), chloroacetyl chloride (124 mg (1.10 mmol)) and pyridine (89 g (1.13 mmol)) in a mixture of dry diethyl ether (8 mL) and dry benzene (16 mL) gave the raw carboxamide. It was mixed with morpholine (174 mg (2.00 mmol)), K2CO3 (276 mg (2.00 mmol)) and NaI (97 mg (0.65 mmol)) in dry acetonitrile (20 mL), giving the tertiary amine which was purified by column chromatography  to yield compound 32 as white amorphous solid (233 mg (62%)). IR = 3326, 2982, 1731, 1595, 1542, 1520, 1462, 1328, 1254, 1216, 1146, 1112, 1041, 1009, 867, 809; 1H NMR  δ = 1.46–1.53 , 2.64 2), 3.24 , 3.68 2), 4.12–4.20 , 7.00 , 7.11 , 7.23 , 9.75 ; 13C NMR  δ = 14.62 (CH3), 14.71 (CH3), 53.79 (N(CH2)2), 61.76 (C-2), 64.69, 65.01 (2 OCH2), 66.85 (O(CH2)2), 113.05 (C-5”), 113.57 (C-2”), 116.84 (C-1”), 120.00 (C-6”), 147.42 (C-3’), 148.30 (C-4’), 149.65 (C-3”), 151.29 (C-4”), 167.80 (C=O); HRMS (EI+) calcd for C18H24N4O5: 376.1747; found: 376.1743.N--1,2,5-oxadiazol-3-yl)-3-(pyrrolidin-1-yl)propanamide (34): The reaction of amino furazan 9 (249 mg (1.00 mmol)), 3-chloropropanoyl chloride (140 mg (1.10 mmol)) and pyridine (89 g (1.13 mmol)) in a mixture of dry diethyl ether (8 mL) and dry benzene (16 mL) gave the raw carboxamide. It was mixed with pyrrolidine (142 mg (2.00 mmol)), K2CO3 (276 mg (2.00 mmol)) and NaI (97 mg (0.65 mmol)) in dry acetonitrile (20 mL), giving the tertiary amine which was purified by column chromatography  to yield compound 34 as yellow amorphous solid (300 mg (80%)). IR = 2977, 1719, 1551, 1476, 1434, 1396, 1323, 1274, 1250, 1217, 1149, 1043, 916, 845; 1H NMR  δ = 1.46–1.51 , 1.53–1.57 2), 2.51–2.56 2), 2.63 , 2.82 , 4.10–4.18 , 6.96 , 7.11 , 7.19 , 12.02 ; 13C NMR  δ = 14.68 (CH3), 14.72 (CH3), 23.35 ((CH2)2), 34.06 (C-2), 51.07 (C-3), 53.08 (N(CH2)2), 64.89, 64.65 (2 OCH2), 112.95 (C-5”), 113.50 (C-2”), 117.36 (C-1”), 120.46 (C-6”), 148.42 (C-3’), 148.71 (C-4’), 149.27 (C-3”), 150.88 (C-4”), 170.64 (C=O); HRMS (EI+) calcd for C19H26N4O4: 374.1954; found: 374.1973.N--1,2,5-oxadiazol-3-yl)-3-(morpholin-4-yl)propanamide (35): The reaction of amino furazan 9 (249 mg (1.00 mmol)), 3-chloropropanoyl chloride (140 mg (1.10 mmol)) and pyridine (89 g (1.13 mmol)) in a mixture of dry diethyl ether (8 mL) and dry benzene (16 mL) gave the raw carboxamide. It was mixed with morpholine (174 mg (2.00 mmol)), K2CO3 (276 mg (2.00 mmol)) and NaI (97 mg (0.65 mmol)) in dry acetonitrile (20 mL), giving the tertiary amine which was purified by column chromatography  to yield compound 35 as white amorphous solid (223 mg (57%)). IR = 3205, 2978, 1677, 1537, 1472, 1375, 1274, 1215, 1142, 1119, 1042, 870, 814; 1H NMR  δ = 1.48 , 2.49 2), 2.64 , 2.72 , 3.36–3.41 2), 4.10–4.17 , 6.96 , 7.15 , 7.19 , 11.28 ; 13C NMR  δ = 14.62 (CH3), 14.70 (CH3), 31.56 (C-2), 52.70 (N(CH2)2), 53.56 (C-3), 64.63 (OCH2), 64.98 (OCH2), 66.17 (O(CH2)2), 113.09 (C-5”), 113.56 (C-2”), 117.09 (C-1”), 120.83 (C-6”), 148.22 (C-3’), 148.95 (C-4’), 149.28 (C-3”), 151.14 (C-4”), 170.19 (C=O); HRMS (EI+) calcd for C19H26N4O5: 390.1903; found: 390.1892.3-Methyl-N-benzamide (39): Method A: The reaction of compound 38 (161 mg (1.00 mmol)), 3-methylbenzoyl chloride (201 mg (1.30 mmol)) and NaH  (80 mg (2.00 mmol)) in dry DMF (16 mL) gave the raw carboxamide which was purified by column chromatography  to yield compound 39 as white amorphous solid (75 mg (27%)). IR = 3288, 1663, 1588, 1566, 1521, 1481, 1383, 1284, 885, 807; 1H NMR  δ = 2.41 , 7.38 , 7.42 , 7.45–7.53 , 7.63 , 7.69 , 7.70 , 8.29 ; 13C NMR  δ = 21.32 (CH3), 124.45 (C-6), 125.29 (C-1”), 127.57 , 128.39 (C-2), 128.88 (C-5), 129.32 , 130.81 (C-4”), 131.99 (C-1), 133.95 (C-4), 139.13 (C-3), 148.73 (C-3’), 149.94 (C-4’), 165.38 (CO); HRMS (EI+) calcd for C16H13N3O2: 279.1008; found: 279.0997.P. falciparum was determined using a 3H-hypoxanthine incorporation assay [1 strain [3 (2.1 g/L), neomycin (100 U/mL), Albumax (5 g/L) and washed human red cells A+ at 2.5% hematocrit (0.3% parasitemia). Serial drug dilutions of 11 3-fold dilution steps covering a range from 100 to 0.002 μg/mL were prepared. The 96-well plates were incubated in a humidified atmosphere at 37 °C; 4% CO2, 3% O2, 93% N2. After 48 h, 0.05 mL of 3H-hypoxanthine (=0.5 μCi) was added to each well of the plate. The plates were incubated for a further 24 h under the same conditions. The plates were then harvested with a Betaplate cell harvester . The red blood cells were transferred onto a glass fiber filter and washed with distilled water. The dried filters were inserted into a plastic foil with 10 mL of scintillation fluid and counted in a Betaplate liquid scintillation counter . IC50 values were calculated from sigmoidal inhibition curves by linear regression [In vitro activity against erythrocytic stages of on assay ,46, usinon assay  or the c1 strain . Chloroqgression  using Mi50 values were calculated by linear regression [Assays were performed in 96-well microtiter plates, each well containing 0.1 mL of RPMI 1640 medium supplemented with 1% L-glutamine (200 mM) and 10% fetal bovine serum and 4000 L-6 cells  ,51. Serigression  from the2 value of the calibration curve was higher than 0.99 [e) was calculated as shown in the following Equations (1)–(3):The PAMPA was performed using a 96-well precoated Corning Gentest PAMPA plate at a pH of 7.4. The PAMPA plate system consists of a donor plate and an acceptor plate. When both plates are coupled, each well is divided into two chambers that are separated by a lipid–oil–lipid trilayer constructed in a porous filter. Stock solutions (10 mM) of each compound were prepared in DMSO and then further diluted to a concentration of 200 µM in phosphate-buffered saline (PBS) at pH 7.4. The compound dissolved in PBS was then added to the donor plate and pure PBS was added to the acceptor plate. Four replicates of each compound and negative control (PBS) were transferred into different wells of the donor plate. Both plates were coupled and left at room temperature for 5 h. Then, the plates were separated, and the solutions of each donor well and acceptor well were transferred to 96-well UV-Star Microplates (Greiner Bio-One). The UV absorbance of compounds in donor wells and acceptor wells were analyzed by a SpectraMax M3 UV plate reader (Molecular Devices). The concentrations were received from a calibration curve for each substance. The plates were analyzed at a wavelength where the Rhan 0.99 . The effeP—effective permeability;S—filter area (0.3 cm2);DV—donor well volume;AV—acceptor well volume;t—incubation time ;Ac(t)—concentration of compound in acceptor well at time t;equc—equilibrium concentration.Dc(t) —concentration of compound in donor well at time t.Recovery of compounds from donor and acceptor wells (mass retention) was calculated as shown in the equation below. Data were only accepted when recovery exceeded 70%.R—mass retention (%);Dc(t)—concentration of compound in donor well at time t;Ac(t)—concentration of compound in acceptor well at time t;c0—initial concentration of compound in donor well;DV—donor well volume;AV—acceptor well volume.Ligand efficiency was calculated as shown in the following Equation (4) :(4)LE=1.LE—ligand efficiency;HA—number of heavy atoms;50—negative logarithm of IC50.pICN-acyl derivatives of 1,2,5-oxadiazol-3-amines. The substitution of the phenyl ring in ring position 4 of the furazan ring has a remarkable impact on the antiplasmodial activity. A compound with an unsubstituted ring was practically ineffective against both strains of P. falciparum, whereas its 3,4-diethoxy analog was active in low nanomolar concentration. Moreover, the activity strongly depended on the nature of the acyl moiety. Benzoyl derivatives were much more active than their alkanoyl analogs. Substitution of the phenyl ring strongly influenced the activity depending on the substituent and its ring position (13 with a 3-(trifluoromethyl) group was highly active against the chloroquine-sensitive strain NF54 but even more active against the multiresistant K1 strain of P. falciparum. Like artemisinin, it possessed activity against this strain in low nanomolar concentration. Compared to the parent compound, it showed improved permeability. Further investigations should reveal if the  substitution is already the optimum in ring position 4 of the furazan ring.This paper deals with the synthesis and antiplasmodial activities of a series of new 4-substituted position . The mos