The trisaccharide beta-D-GlcpNAc-(1----2)-alpha-D-Manp-(1----6)-beta-D-Manp, as its 8-methoxycarbonyloctyl glycoside, is an acceptor selective for N-acetylglucosaminyltransferase V.

Incubation of the trisaccharide acceptor, beta-D-GlcpNAc-(1----2)-alpha-D-Manp-(1----6)-beta-D-Manp-O( CH2)8CO2Me with sonicates of Rous sarcoma-transformed baby-hamster kidney cells, which contain N-acetylglucosaminyltransferase V activity, resulted in the production of beta-D-GlcpNAc-(1----2)-[beta-D-GlcpNAc-(1----6)]-alpha-D-Manp-(1- ---6)- beta-D-Manp-O(CH2)8CO2Me (4). The product of the enzymic reaction was identified by comparison of its 1H-n.m.r. spectrum with that of authentic 4 whose chemical synthesis is also described.