P(1)-(Phenoxyundecyl)-P(2)-(alpha-D-galactopyranosyl) diphosphate as well as P(1)-(11-phenoxyundecyl)-P(2)-(alpha-D-glucopyranosyl) diphosphate are newly synthesized and their ability to serve as substrate-acceptor of mannosyl residue in enzymic reaction catalyzed by mannosyltransferase from Salmonella newport membrane preparation is investigated. The possibility ofgalactosyl-containing derivative to serve as mannosyl acceptor from GDP-Man is established whereas glucosyl-containing compound is inactive in this process.