Stereoselective entry to 1′-C-branched 4′-thionucleosides from 4-thiofuranoid glycal: synthesis of 4′-thioangustmycin C

A stereoselective synthetic method for the synthesis of novel 1′-C-carbon-substituted 4′-thionucleosides has been developed. The present method consists of the following steps: (1) preparation of the 1-C-carbon-substituted 4-thiofuranoid glycals based on lithiation, and (2) NIS- or PhSeCl-initiated stereoselective glycosidation to these 1-substituted glycals. This synthetic sequence enabled us to synthesize the 4′-thio analogue of antitumor antibiotic angustmycin C.