GLYCOSYLATION BY SUGAR 1,2-O-(1-CYANOBENZYLIDENE) DERIVATIVES - INFLUENCE OF GLYCOSYL-DONOR STRUCTURE AND PROMOTER

,2-O-(1-cyanobenzylidene)-alpha-D-galactopyranoses with differently su bstituted aromatic nuclei have been synthesised and used as glycosyl d onors in reactions with the acceptors methyl 4-tri-O-acetyl-6-O-trityl -beta-D-galactopyranoside (11) and methyl 6-tri-O-acetyl-3-O-trityl-be ta-D-galactopyranoside (12). The glycosylation of 11 gave only beta pr oducts. The efficiency and stereoselectivity of the glycosylations of 12 depend on the nature of the substituent in the aromatic ring. The s tereoselectivity for the formation of 1,2-trans-glycosidic bonds was t he highest with the p-methoxy-benzylidene derivative with triphenylmet hylium triflate as the promoter.