Studies on the Phytoalexin Elicitor-Active Substance for the Defensive Mechanism in Plants

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It is generally known that some plants synthesize antimicrobial substances as a defende mechanism against invasive microorganism. These antimicrovial substances synthesized are called phytoalexins, and their inducer is called an elicitor. Matsubara found elicitor activity on a aglycoprotein in a culture fitrate of germinating Mycospharella pinodes conidia and determined its structure to ve a glycosyl chain. In order to investigate the structural requirements for bioactive glycoprotein in detail, we have carried out synthetic studies on the triglycosyl-serine and/or trihlycosyl dipeptide derivatives of a model of the glycopeptide. Glycosylation of the disaccharide, 2,3,4,6-tetra-OMICRON-acetyl-BETA-D-glucopyranosyl-(1-6)-2,3,4-rei-OMICRON-acetyl-ALPHA-D-monnopyranosyl trichloroacetimidate, with NU-(carbovenzoxy)-2,3,4, -tri-OMICRON-acetyl-ALPHA-D-mannlpyranosyl)-(1-3)-L-serine methyl ester or NU-(carbobenzoxy)-(2,3,4, -tri-OMICRON-acetyl-ALPHA-D-mannopyranosyl)-(1-3)-L-seryl-L-proline methyl ester by use of AgOTf gave the desired trisaccharide-serine or trisaccharide-seryl-proline derivatives, which were transformed into BETA-D-dlucopyranosyl-(1-6)-ALPHA-D-monnopyranosyl-(1-6)-PLPHA-D-monnopyranosyl-(1-3)-L-serine and triglycosyl-(1-3)-L-seryl-L-proline via removal of NU-carbobenzoxy group, followed by deacylation. These compounds possess potenitial elicitor activity.