EFFECT OF A NUCLEOPHILIC SUBSTITUENT ON THE STEREO-CHEMISTRY OF THE KOENIGS-KNORR REACTION - STEREOSPECIFIC SYNTHESIS OF SOME ALPHA-LINKED AND BETA-LINKED DISACCHARIDES OF L-FUCOSE

Reaction of 2-O-benzyl-3,4-di-O-p-nitrobenzoyl-α-l-fucopyranosyl bromide with suitably protected benzyl α-l-fucopyranoside, methyl α- and β-l-fucopyranosides, and methyl α- and β-d-galactopyranosides afforded 2-O-α-l-linked disaccharides stereospecifically. Reaction of the same nucleophilic derivatives with 2,3,4-tri-O-acetyl-α-l-fucopyranosyl bromide generally led to the corresponding β-l-linked disaccharides. However, methyl 6-O-benzoyl-3,4-O-isopropylidene-β-D-galactopyranoside gave an appreciable proportion of α-l-disaccharide, whereas benzyl β-l-fuco- and β-d-galacto-pyranosides gave α-l-linked disaccharides stereospecifically. © 1979.