Oligosaccharides Related to Tumor-Associated Antigens. Part I. Synthesis of the propyl glycoside of the trisaccharide ?-L-Fucp-(1 ? 2)-?-D-Galp-(1 ? 3)-?-D-GalpNAc, component of a tumor antigen recognized by the antibody MBr1
The synthesis of the trisaccharide α-L-Fucp-(12)-β-D-Galp-(1 3)-β-D-GalpNAc-1-OPr (2) is described. The N-acetylgalactosamine 6 was obtained from 4 by an intramolecular displacement of a (trifluoromethyl)sulfonyloxy by a pivaloyloxy group with its concomitant migration from position 3 to position 4 (Scheme 1). The galactosyl donor 9 was obtained from 7via8 by regioselective opening of the orthoester