A New DNA Building Block, 4′-Selenothymidine: Synthesis and Modification to 4′-Seleno-AZT as a Potential Anti-HIV Agent

The first synthesis of 4′-selenothymidine (1), a novel DNA building block, and 4′-seleno-AZT (2) was accomplished from 2-deoxy-d-ribose via stereoselective formation of 2-deoxy-4-seleno-d-furanose 17 and a Pummerer-type base condensation as key steps. 4′-Selenothymidine (1) was discovered to adopt the same 2′-endo/3′-exo conformation as thymidine, which is unusual in that 4′-selenouridine has the opposite conformation to that of uridine.