Summaries, structure and reactivity regarding 1,2 : 3,4-disulfite beta-L-arabinopyranosis nucleophiles

Treatment of L-arabinose, at low temperature, with thionyl chloride in the presence of pyridine afforded, in 93% yield, a mixture of the four diastereoisomeric beta-L-arabinopyranose 1,2: 3,4-disulfites. Configurations at the sulfur atoms were determined for each isomer by high resolution H-1-n.m.r. spectroscopy. Reaction of these compounds with various nucleophiles, including bis(trimethylsilyluracil), led in high yields to 1,2-trans-glycosides, unprotected at O-2 and having a cyclic 3,4-sulfite group. The latter compound was substituted by azide ion to give, after benzoylation, 1-(3-azido-2,4-di-O-benzoyl-3-deoxy-alpha-L-lyxopyranosyl) uracil from l-(O-trimethylsilyl-alpha-L-arabinopyranosyl 3,4-sulfite) uracil. Hydrolysis of the cyclic sulfite group of 1-(alpha-L-arabinopyranosyl 3,4-sulfite) uracil afforded l-(alpha-L-arabinopyranosyl) uracil in almost quantitative yield. Thus, this nucleoside was synthesized in 77% overall yield from L-arabinose via beta-L-arabinopyranose 1,2: 3,4-disulfite.