Summary of unprotected pyridimic nucleosides in O-2 ' from cyclic sulfites in C-1-C-2*

Treatment of 3,5,6-tri-O-benzoyl-alpha-D-glucofuranose 1,2-sulfite with an excess of bis(trimethylsil) uracil, in fusion processes without any catalyst, afforded an excellent yield of 1-(3,5,6-tri-O-benzoyl-2-O-trimethylsilyl-beta-D-glucofuranosyl) uracil, which was readily hydrolyzed in slightly acid conditions to give in almost quantitative yield 1-(3,5,6-tri-O-benzoyl-beta-D-glucofuranosyl) uracil. This new synthetic method for nucleosides unprotected at O-2' was also tested in other sugar series. In some cases, only the 1', 2'-trans-nucleosides were obtained, but in others, small yields (3-10%) of 1', 2'-cis-nucleosides were detected. The alpha-to-beta ratio seems to be dependent on the reaction temperature. 2,4-Dimethoxypyrimidine also reacted with sugar 1, 2-sulfites and 4-O-methyl-1-(3,5,6-tri-O-benzyl-beta-D-glucopyranosyl)2-pyrimidinone was prepared in 85% yield from 3,5,6-tri-O-benzyl-alpha-D-glucopyranose 1,2-sulfite.