Abstract
6, 5'-Cyclo-5'-deoxyuridine, a fixed anti form of uridine, was synthesized by a radical cyclization of 5'-bromo (or iodo)-5'-deoxy-2', 3'-O-isopropylidene-5-chloro (or bromo)-uridine with tri-■-butyltin hydride followed by dehydrohalogenation and deacetonation. The 5-bromo and 4-thio derivatives of the cyclouridine were also prepared and were converted to the 2', 3'-cyclic phosphates. These nucleotides were hydrolyzed by pancreatic ribonuclease. The result showed that the enzyme recognizes the pyrimidine nucleotides in the anti form. 6, 5'-Cyclo-5'-deoxycytidine was also synthesized by two routes.