Structure Activity Relations of Polyfunctional Diterpenes of the Tigliane Type, VI¹

A method for the isolation and preparation of 12-deoxyphorbol ( 1) from Euphorbium resin ( EUPHORBIA RESINIFERA Berg) was established to provide substantial amounts of 1-esters for bioassays. Acylation of 1 yielded 12-deoxyphorbol-13,20-diesters ( 2, esters with acids CH (3)(CH (2)) (n)COOH, n = 0, 4, 8, 12, 16, 20; and with benzoic, oleic, elaidic and linoleic acid). Upon mild transesterification the 13,20-diesters 2 yielded the 13-monoesters 3. Both ester types were tested for their irritant activities, the 13-monoesters were also assayed for their tumor-promoting activity. A dependance of both of these activities on the chain length of the acyl residues is noticeable. For both probably a broad maximum exists around the tetradecanoate.