4,4′,4″-Tris(levulinoyloxy)trityl as a New Type of Primary Hydroxyl Protecting Group

Abstract

Abstract The 4,4′,4″-tris(levulinoyloxy)trityl (TLTr) group was introduced selectively on the 5′-oxygen of thymidine by use of in situ generated 4,4′,4″-tris(levulinoyloxy)trityl bromide. The TLTr group was found to be sufficiently stable to acids and readily removed by hydrazinolysis followed by warming to 50 °C in pyridine–acetic acid without damage of other protecting groups such as the O-acetyl and 4,4′-dimethoxytrityl groups. The utility of this new protecting group was demonstrated by the successful synthesis of thymidylyl(3′–5′)-thymidine where the TLTr group was employed as the 5′-hydroxyl-protecting group.