Abstract
Treatment of 5'-acetylthio-5'-deoxy-2', 3'-O-isopropylidene-5-bromouridine, prepared from 2', 3'-O-isopropylidene-5-bromouridine, with sodium methoxide in methanol afforded 5'-deoxy-5'-thio-2', 3'-O-isopropylidene-S6, 5'-cyclouridine. Deacetonation of the product gave 5'-deoxy-5'-thio-S6, 5'-cyclouridine, a sulfur-bridged cyclouridine fixed in the"anti"conformation. Starting from the 5'-amino derivative a N6, 5'-cyclouridine was similarly prepared. The nuclear magnetic resonance and mass spectra of a series of O-, N- and S-cyclouridines were compared and the characteristic features were discussed.
