Asymmetric Hosomi−Sakurai Reaction of Allylsilanes Containing Arabinose-Derived Alcohols as Chiral Auxiliaries

Five enantiopure allylsilanes 1a − e have been prepared, with arabinose-derived alcohols methyl and benzyl 3,4- O -isopropylidene- and 3,4- O -methylene-β- l -arabinopyranosides as chiral auxiliaries, and subjected to the asymmetric Hosomi−Sakurai reaction. The effect of Lewis acid on the stereochemical outcome of the reaction was investigated, and BF 3 was found to exhibit higher enantioselectivity than that of SnCl 4 or TiCl 4 . The reaction of benzyl 2- O -(allyldimethylsilyl)-3,4- O -isopropylidene-β- l -arabinopyranoside ( 1b ) with n -decanal gave the highest ee (45%) in the presence of BF 3 . The steric effect of the chiral auxiliary on the asymmetric Hosomi−Sakurai reaction is demonstrated for the first time although the stereogenic center is remote from the reaction site.