REGIOSELECTIVE FORMATION OF DI-O-BENZYLSUBSTITUTED HEXOPYRANOSIDES VIA STANNYLENE ACETAL INTERMEDIATES

The reactions of dibutylstannylene acetals derived from several methyl hexopyranosides with benzyl bromide have been investigated. These rea ctions occur readily in benzyl bromide at 85 degrees C. At reaction ti mes of one to two days, the major products are di-O-benzyl derivatives . In several cases, single di-O-benzyl derivatives are the predominant products: methyl alpha-D-glucopyranoside and methyl beta-D-galactopyr anoside gave the 2,6- and 3,6-di-O-benzyl ethers in 82 and 70% yields, respectively. The species present in these reactions and the reaction pathway are discussed.