Branched-chain nucleosides: Synthesis of 3'-deoxy-3'-C-hydroxymethyl-alpha-L-lyxopyranosyl thymine and 3'-deogy-3'-C-hydroxymethyl-alpha-L-threofuranosyl thymine.

The synthesis of 3'-deoxy-3'-C-hydroxymethyl branched nucleosides with alpha-L-lyxopyranosyl and alpha-L-threofuranosyl sugar moieties is described The synthetic scheme makes use of a furanose --> pyranose conversion and of the formation of both furanose and pyranose nucleosides during Vorbruggen sugar-base condensation reaction starting from tetra-O-acetyl-3-deoxy-3-C-hydroxymethyl-L-lyxo-(1,6)-furanose. The conformation of the target molecules is discussed.