2 SYNTHETIC ROUTES TO 3'-DIDEOXY-3'-C-(HYDROXYMETHYL)-4'-THIONUCLEOSIDES

A number of 3'-dideoxy-3'-C-(hydroxymethyl)-4'-thionucleosides have be en prepared from either rt-butyldimethylsiloxymethyl)tetrahydrofuran-2 -one or from R,3R)-1-benzyloxy-3(benzyloxymethyl)hex-5-en-2-ol. The fo rmer was converted into methyl dimethylsiloxy)-3-(tert-butyldimethylsi loxymethyl) and then into 1-0-acetyl-2,3-dideoxy-3-C- butyldimethylsil yl)-4-thio-D-evythro-pentofuranose prior to coupling with silylated py rimidines. The second key intermediate was converted into benzyloxymet hyl-5,5-bis(benzylsulfanyl)pentan-2-ol and thence via the mesyl ester into yl)-2,3-dideoxy-1,4-dithio-D-erythro-pentofuranose prior to coupl ing with silylated pyrimidines.