Chiral Aldehydes by Ring Contraction of Pento- and Hexopyranoside Epoxides

Article abstract of DOI:10.1021/jo00307a017

The chiral aldehydes (-)-(2S,5S)- and (-)-(2S,5R)-2-<<oxy>methyl>-5-methoxy-2,5-dihydrofuran-3-carbaldehyde (2 and 4) were synthesized in 60 and 15percent yield, respectively, by lithium bromide induced rearrangement of 6-O-silylated methyl 2,3- and 3,4-anhydro-α- and -β-D-hexopyranosides, obtained in two steps from methyl α- and β-D-glucopyranoside.Rearrangement of various other pento- and hexoside epoxides permitted the suggestion of probable reaction routes.Hydrogenation of the unsaturated aldehydes gave the corresponding saturated aldehydes in good yield.