CONVERGENT SYNTHESIS OF 2',3'-DIDEOXY-3'-MERCAPTO NUCLEOSIDES - POTENTIAL ANTI-HIV AGENTS

Methyl io-5-O-tert-butyldiphenylsilyl-2,3-dideoxy-beta-D- erythro-pent ofuranoside (4) and its corresponding alpha anomer 5 were synthesized in four steps from 2-deoxy-D-ribose and used as substrates for the syn thesis of nucleosides by condensation with silylated thymidine and N-6 -isobutyryladenine. The nucleosides were deprotected by treatment with Bu(4)NF in THF followed by reaction with MeONa in MeOH to give 3'-deo xy-3'-mercaptothymidine (8), 2',3'-dideoxy-3'mercaptoadenosine (15) an d its corresponding alpha anomer 16. In the latter reactions it was im portant to use degassed solvents to minimize formation of the correspo nding disulfides of purine nucleosides. Using Bu(4)NF, without subsequ ent reaction with MeONa in the deprotection reaction, resulted in inte rmolecular transesterification reactions.