Vesicant principles of Poison Ivy and related plants: synthesis of the urushiols, 1,2- dihydroxy-3-[(Z)-pentadec-8-enyl]benzene and 1,2 dihydroxy-3-pentadecylbenzene

Abstract

New syntheses of 1,2-dihydroxy-3-[(Z)-pentadec-8-enyl]benzene (1) and 1,2-dihydroxy-3-pentadecylbenzene (4), vesicant principles of Poison Ivy (Rhus radicans) and other species of Anacardiaceae, are described starting from 1,2-dimethoxybenzene (7). The lithiation of 1,2-dimethoxybenzene (7) has been re-examined and the yield of the product, 2,3-dimethoxyphenyl-lithium (8), re-determined. The reaction of this aryl-lithium with 1,7-dibromoheptane has been studied by g.I.c., using tributyltin chloride as a quenching reagent. The extracts of two plants of the Anacardiaceae family, Semecarpus vitiensis Engl. and Melanorrhoea beccari Engl., have been examined for the presence of urushiols. The bark of the latter has been found to contain gallic acid.