Improved access to highly unsaturated skin irritants of the daphnane type from latex of Excoecaria oppositifolia.

A new and more efficient procedure was developed to obtain 5 beta-hydroxyresiniferonol-6 alpha,7 alpha-epoxide- 9,13,14-ortho(2,4,6-decatrienoate) [Excoecaria factor O1] by alkaline transesterification of corresponding 20-ester(s) genuinely present in latex of Excoecaria oppositifolia. It was obtained in a 10-fold better yield than previously, probably due to speeding up the separation procedures of the sensitive compound. O1 is an appropriate starting material for the preparation of the daphnane prototype irritant and tumor-promoting orthoester simplexin (SIM) especially of a multiple tritium-labeled form thereof. Moreover, a new Excoecaria factor O3, i.e. the 9,13,14-ortho(2,4,6,8-hexadecate-traenoate) of 5 beta,12 beta-dihydroxyresiniferonol-6 alpha,7 alpha-epoxide was isolated after alkaline transesterification of a TLC-uniform fraction, composed of corresponding 20-ester(s).