3-Aminopropyl O-(β-d-galactopyranosyl)-(1→4)-O-(β-d-glucopyranosyl)-(1→6)-O-{3-O-[(S)-1-carboxyethyl]-β-d-galactopyranosyl-(1→4)-O}-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-(1→3)-O-(β-d-galactopyranosyl)-(1→4)-β-d-glucopyranoside (18) was synthesized by block condensations from suitably protected acceptors and donors, namely 3-azidopropyl 4-O-(2,4,6-tri-O-acetyl-β-d-galactopyranosyl)-2,3,6-tri-O-acetyl-β-d-glucopyranoside (5), phenyl 3-O-benzyl-4,6-di-O-isopropylidene-2-deoxy-2-phthalimido-1-thio-β-d-glucopyranoside (7), 2,4,6-tri-O-acetyl-3-O-[(S)-1-(methoxycarbonyl)ethyl]-α-d-galactopyranosyl trichloroacetimidate (11), and 4-O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)-2,3,6-tri-tri-O-acetyl-α-d-glucopyranosyl trichloroacetimidate (14). Compound 18 contains structural elements of type III group B Streptococcus capsular polysaccharide in which terminal sialic acid is replaced by an (S)-1-carboxyethyl group, and has a short spacer for the conjugation with peptide or protein.