Isoneorautenol and other pterocarpan phytoalexins from calopogonium mucunoides

Abstract

Following inoculation with the fungus Helminthosporium carbonum, excised leaflets of the tropical papilionate legume Calopogonium mucunoides have been found to produce isoneorautenol, a new dimethylpyrano-substituted isoflavonoid (pterocarpan) phytoalexin. This com pound accumulates together with dem ethylm edicarpin, neodunol, tuberosin, sophorapterocarpan A, and a sixth highly antifungal isoflavonoid (calopocarpin) characterised as 3,9-dihydroxy-2-(3,3-dimethylallyl)pterocarpan. Chromatographic and spectroscopic examination of’hom oedudiol’(a pterocarpan from Neorautanenia edulis roots previously considered to possess the structure now assigned to calopocarpin) has shown that in reality this substance is identical with sophorapterocarpan A.The systematic relationship of C alopogonium to other genera with in the legum e tribe Phaseoleae is briefly discussed. © 1985, Walter de Gruyter. All rights reserved.