Synthesis of the antigenic tetrasaccharide side chain from the major glycoprotein of Bacillus anthracis exosporium

A synthesis of the pentenyl glycoside of the tetrasaccharide side chain from the major glycoprotein of Bacillus anthracis by a [3 + 1] approach is described. The construction of the 1,2-trans-glycosidic linkage in the terminal anthrose moiety was achieved through the application of known alpha-nitrilium ion-mediated beta-selective glycosylation methodology. An iterative glycosylation strategy was used for the assembly of the trirhamnan building block. A new route to the anthrose saccharide was developed from D-galactose.