Halogenium-Induced Cyclization of 5-Substituted 6, 2'-O-Cyclouridine

Abstract

Reaction of 5-chloro (or bromo)-6, 2'-O-cyclouridine (IIa or IIb) with N-bromo(or chloro)-succinimide gave 5-bromo-5-chloro-5, 6-dihydro-6, 2' : 6, 5'-di-O-cyclouridine (VI). A similar reaction of 5-nitro-6, 2'-O-cyclouridine (VII) afforded the 5-chloro(or bromo)-5-nitro analog (VIII or IX). Both VI and VIII were mixtures of two diastereoisomers and each isomeric mixture was separated by preparative high-performance liquid chromatography. The steric configurations and mass spectra of VI, VIII and IX are discussed.