Allyl 2- O-benzoyl-4, 6- O-benzylidene-α-n-glucopyranoside ( 3), obtained by selective benzoylation of allyl 4,6- O-benzylidene-α- d-glucopyranoside ( 2) with benzoyl chloride- imidazole in anhydrous chloroform, reacted with 2, 3, 4-tri- O-benzoyl-α- l-rhamnopyranosyl bromide to give a disaccharide derivative ( 4), and an important intermediate ( 5) was obtained by cleavage of its acetal. Treatment of 5 with a series of glycopyranosyl bromides, protected by acetyl or benzoyl groups in benzene-nitromethane in the presence of Hg(CN) 2 as a catalyst afforded four trisaccharides ( 6-9). The disaccharide ( 5) and trisaccharides ( 6-9) constitute the sugar cores of phenylpropanoid glycosides. A new glycosyl anomeric leaving group, trichloroacetoxy, was employed to prepare the disaccharide ( 4) and trisaccharides residue ( 8) efficiently and with high stereoselectivity.