Synthesis of allyl 2-O-(alpha-L-arabinofuranosyl)-6-O-(alpha-D-mannopyranosyl)-beta-D-mannopyranoside, a unique plant N-glycan motif containing arabinose

The synthesis of the trisaccharide allyl 2-O-(alpha -L-arabinofuranosyl)-6- O-(alpha -D-mannopyranosyl)-beta -D-mannopyranoside is reported. Stereosele ctive glycosylation at C-6 of a non-protected allyl beta -mannoside with th e acetylated alpha -D-mannosyl bromide gave the alpha-(1 --> 6)-disaccharid e as the main product and the crystalline 3,6-branched trisaccharide as min or compound. Further glycosylation of the 2,3 diol (1 --> 6) disaccharide w ith L-arabinofuranosyl bromide furnished a mixture of 3-O- and 2-O-alpha -L -Ara-trisaccharides from which the title compound was isolated. (C) 2000 El sevier Science Ltd. All rights reserved.