Nucleosides and Nucleotides. IX. Synthesis of Sulfur-bridged Cyclonucleosides : (S)-2, 2'-, 2, 3'-, and 2, 5'-Cyclo-2-thiouridines

Abstract

Three sulfur-bridged cyclonucleosides, (S)-2, 2'-, 2, 3'-and 2, 5'-cyclo-2-thiouridines (VII, XV, and XIV) have been synthesized. The present synthetic method involves the use of uridine as the starting material through 2-thiouridines as the intermediates. The ultraviolet, optical rotatory dispersion (ORD), circular dichroism (CD), and nuclear magnetic resonance data of these (S)-cyclo-2-thiouridines are presented. (S)-2, 5'-Cyclonucleoside (XIV) was thought to be present as an "endo" conformation in terms of bridging sulfur. The limitation of the applicability of Ulbricht's rule on the correlation of the sign of ORD (CD) and torsion angle around the glycosidic bond was discussed.