SYNTHESIS OF SOME 6-SUBSTITUTED 5-AZACYTIDINES

Protected 6-substituted benzyl, phenyl and chloromethyl derivatives of 5-azacytidine 8-10 have been prepared by addition of phenylacetyl- (2 ), benzoyl- (3) or (chloroacetyl)guanidine (4) to 2,3,5-tri-O-benzoyl- beta-D-ribosyl isocyanate (1) and subsequent silylation-mediated cycli zation of the obtained acyl(carbamoyl)guanidines 5-7. 4-Amino-6-phenyl -1,3,5-triazin-2(1H)-one (12) was obtained by condensation of carbamoy lguanidine (13) with methyl benzonte in presence of methanolic sodium methoxide or by condensation of 13 with triethyl orthobenzoate in N,N- dimethylformamide. Stannic chloride catalyzed condensation of silylate d 6-phenyl derivative 11 with 1-O-acetyl-2,3,5-tri-O-benzoyl-beta-D-ri bose (14) in 1,2-dichloroethane afforded a 1.2:1 mixture of N-1 and N- 3 nucleosides 9 and 15, respectively. Methanolysis of the protected co mpounds 8-10 and 15 gave the respective free nucleosides 16-19. The la tter compounds inhibited the growth of bacteria E. coli B to a much lo wer extent than the unsubstituted 5-azacytidine.