SYNTHESIS OF A GLYCOPEPTIDE WITH PHYTOALEXIN ELICITOR ACTIVITY .1. SYNTHESES OF A TRIGLYCOSYL-L-SERINE AND A TRIGLYCOSYL L-SERYL-L-PROLINE DIPEPTIDE

A stereocontrolled synthesis of the model compound for the phytoalexin elicitor-active glycoprotein is described. Glycosylation of the disac charide, 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl-(1 --> 6)-2,3,4- tri-O-acetyl-alpha-D-mannopyranosyl trichloroacetimidate, with xy)-(2, 3,4-tri-O-acetyl-alpha-D-mannopyranosyl)-(1 --> 3)-L-serine methyl est er or xy)-(2,3,4-tri-O-acetyl-alpha-D-mannopyranosyl)-(1 --> 3)-L-sery l-L-proline methyl ester by use of AgOTf gave the desired trisaccharid e-serine or trisaccharide-seryl-proline derivatives, which were transf ormed into beta-D-glucopyranosyl-(1 --> 6)-alpha-D-mannopyranosyl-(1 - -> 6)-alpha-D-mannopyranosyl-(1 --> 3)-L-serine and triglycosyl-(1 --> 3)-L-seryl-L-proline via removal of the N-carbobenzoxy group, followe d by deacylation.