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