Synthesis and reaction of some 6-substituted pyrimidine nucleosides

Treatment of 5-bromouridines with sodium cyanide afforded 6-cyanouridines. Further treatment of the 6-cyano derivatives with cyanide ion at higher temperature gave the 5-cyanouridines. The 6-cyano group was transformed to thioamido, carboxy, chloromethyl cyanomethyl, carboxymethyl, and methyl group, respectively. 5-Bromocytidines were also converted to the 6-cyanocytidines, from which cytidine 6-carboxylic acid was derived. The cyano group of 6-cyanocytidines has a leaving ability toward nucleophilic substitution reactions. The circular dichroic spectra of various 6-substituted pyrimidine nucleosides showed positive Cotton effect at B2u region, which were in contrast to the reported negative bands in 6-methyl-uridine or-cytidine.