Absolute configuration of volicitin, an elicitor of plant volatile biosynthesis from lepidopteran larvae

The absolute configuration of the hydroxylinolenoyl moiety of volicitin (17-hydroxylinolenoyl-l-glutamine) 1a/b from four lepidopteran larvae was determined by methanolysis and derivatisation of the resulting ester with (1R)-1-phenyl-ethylisocyanate 3. The absolute configuration of the resulting (1′R)-17-(1′-phenyl-ethylcarbamoyloxy)-methyl linolenoates 4a/b followed from GLC comparison with synthetic references. Natural volicitin 1 from caterpillars of Spodoptera exigua, S. frugiperda, S. littoralis and Heliothis virescens (Noctuidae) exhibits a high ee (92–96%) and has a 17S configuration.