ONE-POT SYNTHESIS OF BETA-D-GALF(1-]4)[BETA-D-GALP(1-]6)]-D-GLCNAC, ACORE TRISACCHARIDE LINKED O-GLYCOSIDICALLY IN GLYCOPROTEINS OF TRYPANOSOMA-CRUZI

Tin(IV) chloride-promoted condensation of benzyl tamido-3-O-benzoyl-2- deoxy-alpha-D-glucopyranoside (4) with penta-O-benzoyl-beta-D-galactop yranose (6) gave the derivative of beta-D-Galp-(1 --> 6)-alpha-D-GlcNA c 7 in 80% yield, This was glycosylated with penta-O-benzoyl-alpha,bet a- D-galactofuranose (5>, employing the same catalyst, to afford the p rotected benzyl per-O-benzoyl-beta-D-Galf(1 --> 4)[beta-D-Galp(1 --> 6 )]D-GlcNAc 10 in 41% yield, Alternatively, compound 10 was obtained di rectly in a one-pot reaction from 4, by sequential addition of 6 and 5 (34% yield). beta-Glycosidic linkages were diastereoselectively forme d. De-O-benzoylation of 10, followed by heterogeneous catalytic transf er hydrogenolysis of the benzyl group afforded the free trisaccharide beta-D-Galf(1 --> 4)[beta-D-Galp(1 --> 6)]-D-GlcNAc (14) in 98% yield from 10. Sodium borohydride reduction of 14 gave the corresponding ald itol, whose spectral data were identical to those reported for the ald itol obtained from the 38-43 kDa cell-surface glycoprotein of Trypanos oma cruzi. (C) 1998 Elsevier Science Ltd.