Crystalline 2,3,6,-tri- O-benzoyl-4- O-(bromoacetyl)-α- d-galactopyrasonyl chloride ( 5) was prepared from methyl 2,3,6-tri- O-benzoyl-4- O-(bromoacetyl)-α-or- or -β-β-galactopyranoside by cleavage with dichloromethyl methyl ether (DCMME) in the presence of zinc chloride. Silver trifluoromethanesulfonate (triflate) condensation of 5 with methyl 2,3,6-tri- O-benzoyl-β- d-galactopyranoside gave the corresponding β-linked disaccharide, which was O-de(bromoacetyl)ated and the resulting disaccharide nucleophile condensed with 5. The β-linked trisaccharide obtained was deprotected, to give the methyl β-glycoside of (1→4)-β-linked β-galactotriose. Compound 5 was converted in high yield into the corresponding 1- O-β-acetyl derivative, which was O-de(bromoacetyl)ated with thiourea to afford crystalline 1- O-acetyl-2,3,6-tri- O-benzoyl-β- d-galactopyranose ( 9). Condensation of 9 with 5 yielded O-[2,3,6-tri- O-benzoyl-4- O-(bromoacetyl)-β- d-galactopyranosyl]-(1→4)-1- O-acetyl-2,3,6-tri- O-benzoyl-β- d- galactopyranose ( 17), which was cleaved with DCMME to give the corresponding glycosyl chloride ( 20). The same sequence of reactions involving 1,2,3,6-tetra- O-benzoyl-α- d-galactopyranose and 2,3,4,6-tetra- O-benzoyl-α- d-galactopyranosyl bromide afforded O-(2,3,4,6-tetra- O-benzoyl-β- d-galactopyranosyl)-(1→4)-2,3,6-tri- O-benzoyl-α- d-galactopyranosyl chloride, which can be used to construct in an oligosaccharide the terminal, β-linked (1→4)-β- d-galactobiosyl group. Compounds 5, 17, and 20, when used as glycosyl donors, allow further chain extension at O-4 of the (terminal) β- d-galactopyranosyl group. The structures of all mono- and di-saccharide intermediates, including those of orthoesters formed during glycosylations under neutral conditions, were confirmed by combination of homo- and hetero-nuclear-correlation n.m.r. experiments. The sites of glycosidic linkages in orthoesters were directly determined by 1 D INAPT n.m.r. experiments. Characteristic features of the 1H- and 13C-n.m.r. spectra of orthoesters which distinguish them from the corresponding oligosaccharides have been summarized.