Synthesis of the Propyl Glycoside of the Trisaccharide alpha-L-Fucp-(1-2)-beta-D-Galp-(1-3)-beta-D-GalpNAc, Component of a Tumor Antigen Recognized by the Antibody MBr1.

The synthesis of the trisaccharide α‐L‐Fucp‐(1 → 2)‐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 7 via 8 by regioselective opening of the orthoester function with AcOH/pyridine followed by treatment with CCl₃CN and 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) (Scheme 2). Glycosylation of 6 with 9 in the presence of BF₃ · OEt₂ gave the disaccharide 10. Selective deprotection of 10 at OC(2′) followed by glycosylation with 12 and by standard deprotection afforded the title trisaccharide 2 (Scheme 3). Preliminary biological testing showed that 2 is able to inhibit the binding of the monoclonal antibody MBrl to the target tumor cells MCF7 in a dose‐dependent manner.