Synthetic Studies on the IsomericN-Methyl Derivatives ofC-Ribavirin

Novel synthesis of seco type of acyclo C-nucleosides of 1,2,4-triazole and 1,2,4-triazol

The seco C-nucleosides 3-(1,2,3,4,5-penta-O-acetyl-D-gluco- and D-galacto-pentitol-1-yl)-1H-1,2,4-triazoles (8 and 9) were obtained in a one pot by deamination and dethiolation of 4-amino-3-(D-gluco- and D-galacto-pentitol-1-yl)-5-mercapto-1,2,4-triazoles (1 and 2), respectively, using sodium nitrite in orthophosphoric acid and subsequent acetylation. Condensation of 1, 2, and 4-amino-3-(D-glycero-D-gulo-hexitol-1-yl)-5-mercapto-1,2,4-triazole (12) with phenacylbromide (11) afforded the corresponding 3-(D-gluco-, D-galactopentitol-1-yl) and 3-(D-glycero-D-gulo-hexitol-1-yl)-6-phenyl-7H-1,2,4-triazolo[3,4-b][1,3,4] thiadiazines (15, 16, and 17). Acetylation of 15-17 gave the penta- and hexa-O-acetyl derivatives 18-20, respectively. The structures were confirmed by using 1H, 13C, and 2D NMR spectra, DQFCOSY, HMQC, and HMBC experiments. The favored conformational structures were deduced from the vicinal coupling constants of the protons.

Synthesis and antiviral activity of 1,5- and 1,3-dialkyl-1,2,4-triazole C-nucleosides derived from 1-(chloroalkyl)-1-aza-2-azoniaallene salts

Reactions of alpha,alpha'-dichloroazo compounds 2 with SbCl5 gave 1-(chloroalkyl)-1-aza-2-azoniaallene salts 3 as reactive intermediates. Cycloadditions of 3 with the ribofuranosyl cyanide 4 afforded the beta-D-ribofuranosyl-1,2,4-triazolium salts 5, which rearranged spontaneously to salts 6. Hydrolysis of 6 gave the 1,2,4-triazole C-nucleosides 7, which yielded the free nucleosides 8 after deblocking. Analogously, 12 was prepared from the cycloaddition of 4 with the alpha-chloroazo compound 10 in the presence of SbCl5. Deblocking of 12 with sodium methoxide afforded 13. Compounds 8a,b,e,f and 13 were tested against HIV-1, HIV-2, HSV-1 and HSV-2 and were found to be inactive.