Allyl 4-O-benzyl-alpha-L-rhamnopyranoside was converted into allyl 4-O-benzyl-3-O-methyl-alpha-L-rhamnopyranoside and this was condensed with 2,3,4-tri-O-acetyl-alpha-L-rhamnopyranosyl chloride to give a disaccharide derivative which was converted into allyl 4-O-benzyl-2-O-(2,3-O-isopropylidene-alpha-L-rhamnopyranosyl)-3-O-methyl -alpha- L-rhamnopyranoside. This disaccharide derivative was condensed with 2,4-di-O-acetyl-3,6-di-O-methyl-alpha-D-glucopyranosyl chloride to give a trisaccharide derivative which was converted into the title compound. This compound represents the oligosaccharide portion of the major serologically active glycolipid from Mycobacterium leprae which is required to prepare a synthetic diagnostic agent for leprosy infection at an early stage and to investigate the specificities of monoclonal antibodies directed towards the glycolipid.