REGIOSELECTIVE GLYCOSYLATION OF N-PROTECTED L-RHAMNO(FUCO) PYRANOSYLAMINES - PREPARATION AND SPECTROSCOPIC CHARACTERIZATION OF BUILDING-BLOCKS FOR NEOGLYCOCONJUGATE SYNTHESES

The regioselective glycosylations of N-2-bis(ethoxycarbonyl)vinyl-beta-L-rhamno- (1) and fucopyranosylamine (2) with tetra-O-acetyl-alpha-D-glycopyranosyl bromides were performed. In this way the N-protected disaccharide and trisaccharide beta-D-Glcp-(1-->3)-beta-L-Rhap (3), beta-D-Glcp-(1-->4)-beta-L-Rhap (5), beta-D-Galp-(1-->3)-beta-L-Rhap (7), beta-D-Galp-(1-->4)-beta-L-Rhap (9), beta-D-Glcp-(1-->3)-beta-L-Fucp (11), beta-D-Glcp-(1-->2)-beta-L-Fucp (13), and beta-D-Galp-(1-->3)-[beta-D-Galp-(1-->3)]-beta-L-Rhap (14) glycosylamines were obtained. The structures of compounds 3, 5, 7, 9, 11, 13, and 14 are supported by the preparation of the corresponding per-O-acetyl derivatives and by spectroscopic (IR, NMR, and MS) data.