A convenient method for the conversion of β-thymidine to α-thymidine based on TMSOTf-mediated C1′-epimerization

A practically useful method for the synthesis of α-thymidine from β-thymidine was developed by trimethylsilyl triflate-mediated C1′-epimerization. When 5′-O-diphenylacetyl-3′-O-toluoylthymidine was trimethylsilylated and successively treated with TMSOTf in acetonitrile, the resulting α-thymidine derivative was crystallized and isolated without silica-gel column chromatography. Deprotection gave unprotected α-thymidine in an overall yield of 50% from β-thymidine.