A synthesis of the target trisaccharide is described in which the key beta-mannosylation is achieved in high yield and selectivity through reaction of the sulfoxide 7 with acceptor 8, mediated with triflic anhydride. The beta-xylosylation was best conducted using tribenzoyl xylopyranosyl bromide and silver triflate. (C) 1998 Elsevier Science Ltd. All rights reserved.