Glycosidation of 3,4,6-Tri-O-Benzyl-2-Ethenyl-D-Glucal – A Route to 2-C-(β-Methyl)Methylene Glycosides

ABSTRACT Monosaccharidic and disaccharidic 2-C-(β-methyl)methylene glycosides were synthesized by an electrophilic conjugate addition reaction of ROH-type compounds in the presence of Ph3P+H Br− to 2-ethenyl-3,4,6-tri-O-benzyl-D-glucal 1, functioning as a model glycosyl donor. This 2-vinyl glucal derivative represents a series of 2-vinyl and 2-butadienyl glycals, prepared by Wittig-type methylenation of pyranosidic conjugated enals, derived from glucal, galactal and lactal. The exo-(β-methyl)methylene group paves the way for further chemical transformations.