Synthesis of Some 6-Substituted 5-Azacytidines

Abstract

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-β-D-ribosyl isocyanate (1) and subsequent silylation-mediated cyclization 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 carbamoylguanidine (13) with methyl benzoate in presence of methanolic sodium methoxide or by condensation of 13 with triethyl orthobenzoate in N,N-dimethylformamide. Stannic chloride catalyzed condensation of silylated 6-phenyl derivative 11 with 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribose (14) in 1,2-dichloroethane afforded a 1.2 : 1 mixture of N1 and N3 nucleosides 9 and 15, respectively. Methanolysis of the protected compounds 8-10 and 15 gave the respective free nucleosides 16-19. The latter compounds inhibited the growth of bacteria E. coli B to a much lower extent than the unsubstituted 5-azacytidine.