TSAO ANALOGS - STEREOSPECIFIC SYNTHESIS AND ANTI-HIV-1 ACTIVITY OF 1-[2',5'-BIS-0-(TERT-BUTYLDIMETHYLSILYL)-BETA-D-RIBOFURANOSYL]-3'-SPIRO-5''-(4''-AMINO-1'',2''-OXATHIOLE 2'',2''-DIOXIDE)PYRIMIDINE AND PYRIMIDINE-MODIFIED NUCLEOSIDES

Several analogues of a new lead for anti-HIV-1 agents [1-[2',5'-bis-O-(tert-butyldimethylsilyl)-beta-D-ribofuranosyl]-thymine]-3'-spiro-5''-(4''-amino-1'',2''-oxathiole 2'',2''-dioxide) (TSAO) modified at positions N-3, 0-4 and C-5 of the thymine moiety, have been prepared and evaluated as inhibitors of HIV-1 replication. A new stereoselective synthetic procedure is described. Reaction of 1,2-di-O-acetyl-5-O-benzoyl-3-C-cyano-3-O-mesyl-D-ribofuranose with pyrimidine bases, followed by treatment with Cs2CO3 afforded stereoselectively, beta-D-ribofuranosyl-3-spiro nucleosides 2',5'-O-Deacylation and subsequent treatment with tert-butyldimethylailyl chloride gave the TSAO derivatives. Only those analogues having a tBDMSi group at both the C-5' and C-2' positions of the ribose moiety showed potent anti-HIV-1 activity. The activity ranged from 0.060-mu-M to 1.0-mu-M. Introduction of an alkyl or alkenyl function at N-3 of the thymine ring markedly decreased cytotoxicity without affecting the antiviral activity. While markedly active against HIV-1, the TSAO derivatives had no activity against HIV-2 or SIV. They represent the first example of nucleoside analogues with an intact ribose moiety that discriminate between HIV-1 and other retroviruses.