The Use of Grignard Reagents in the Synthesis of Carbohydrates. I. The Synthesis of Deoxy and Branched-chain Deoxy Sugars

Article abstract of DOI:10.1246/bcsj.53.222

Two branched-chain deoxy sugars, methyl 5,6-O-cyclohexylidene-3-deoxy-2-C-methyl-β-D-arabino-hexofuranoside and its α-D-ribo isomer, were easily prepared by the one-step reaction of methyl 5,6-O-cyclohexylidene-3-O-mesyl-β-D-allofuranoside (3a) with methylmagnesium iodide.Similarly, the corresponding α-mesylate (4a) gave methyl 5,6-O-cyclohexylidene-3-deoxy-2-C-methyl-α-D-ribo-hexofuranoside.It was demonstrated that these reactions involved 1,2-hydride shifts.The reactions of 3a and 4a with t-butylmagnesium bromide yielded two deoxy sugars, methyl 5,6-O-cylohexylidene-3-deoxy-β-D-arabino-hexofuranoside and the corresponding α-D-ribo isomer, respectively.Under certain reaction conditions with the Grignard reagents, the sulfonate (3a) afforded dimeric compounds, in which two furanose rings were directly bound with a carbon-carbon bond.A convenient method for the preparation of the sulfonates (3a and 4a) is also reported.