N.m.r. studies of the flexibility of the glycosyl ring in thymidine and uridine nucleosides

Abstract

1H-N.m.r. spectroscopy at various temperatures has been used to investigate the flexibility of the glycosyl ring and to calculate the percentage of N- and S-character in the most favoured conformations in solution adopted by various pyrimidine deoxyribonucleosides. The position and orientation of substituents have a definite and predictable influence on the conformation of the deoxyribose ring in these nucleosides. The deoxyribose rings in the nucleosides studied were, in general, flexible except for those of 3'-deoxy-3'-fluoro- and 3'-azido-3'-deoxy-thymidine and 2'-deoxy-2'-fluoro-5-methyl-arabinosyluracil.