C-linked disaccharide derivatives mimicking O-beta-D-galactopyranosyl-(1-->3)-D-galactopyranosides (end groups in Core-B structures of biologically important proteoglycans) have been obtained from isolevoglucosenone and beta-D-galactopyranosylcarbaldehyde derivatives. The beta-D-galactopyranosyl-(1-->3)-CH(OH)-D-galactal derivatives 3a (4,6-di-O-acetyl-3-C-[(1R)-1,3,4,5,7-penta-O-acetyl-2,6-anhydro-D-glycer o-mannno-heptitol-1-C-yl]-3-deoxy-D-galactal), 3b (4,6-di-O-benzyl-3-C-[(1R)-2,6-anhydro-1,3,4,5,7-penta-O-benzyl-D-glycer ocero-L-manno-heptitol-1-C-yl]-3-deoxy-D-galactal) and the beta-D-galactopyranosyl-(1-->3)-CH2-D-galactal 3c (4,6-O-diacetyl-3-C-) [6-O-acetyl-2,3,4-tri-O-(tert-butyl)dimethylsilyl-beta-D-galactopyranosy l-methyl]-3-deoxy-D-galactal have been prepared. One of them, 3a, has been shown to be a suitable agent for the O-glycosidation and the construction of glycoconjugates bearing the beta-D-Galp-(1-->3)-CH(OH)-D-Galp-O moiety. (C) 2004 Elsevier Ltd. All rights reserved.