X-ray analysis of 2',3'-lyxoanhydrothymidine, a conformationally restricted inhibitor of retroviral reverse transcriptases.

2',3'-Lyxoanhydrothymidine (LAT), a conformationally restricted inhibitor of retroviral reverse transcriptases, has been studied by X-ray analysis. The unit cell contains two crystallographically independent molecules A and B. Their sugar moieties have an identical structure: an 04'-endo pucker of the furanose cycle and a trans conformation about the exocyclic C4'-C5' bond. The conformations of A and B molecules differ with respect to the N-glycosidic bond: chi A(04 'Cl' N1C2) = -121.9 degrees which is typical of a common anti conformation whereas chi B (04'Cl'N1C2) = 121.2 degrees corresponds to a rare high-syn conformation. All the conformation properties of LAT molecules stem from the presence of an epoxide cycle in their molecules.