The Structural Identification of the O;efinic Components of Japanese Lac Urushiol

The heteroolefinic composition of urushiol, the vesicant principle of Japanese lac, has been confirmed. By means of chromatography on alumina the dimethyl ether has been separated intio four components whose structures have been established. All of the components of urushiol have the carbon skeleton of 3-pentadecylcatechol. A monoolefin, diolefin and triolefin account for about 95% of the urushiol. The fourth component has the saturated side chain. The structueres of the die- and triolefinic components have been found to be different from those proposed earlier by Majima.The major difference between the alkenyl catechols of Japanese lac and poison ivy is found in the triolefinic components. The lac triolefin, which constitutes about 50% of urushiol, possesses a conjugated diene system. The corresponding triolefin of poison ivy has no conjugation.