Synthesis of Thymine Nucleosides Derived from 1-Deoxy-D-psicofuranose

The use of D-(+)-ribonic γ-lactone 1a,b as a chiral synthon leads to an efficient synthesis of the ketose 1-deoxy-D-psicofuranose 2a,b. Condensation of the corresponding acetyl derivative 3a,b with silylated thymine, followed by deprotection of 4a,b affords an anomeric mixture of ketosyl nucleoside 6 (predominately the β-anomer) in an improved overall yield of 49%.