On the Active Principles of the Thymelaeaceae

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Abstract
The toxic and irritant diterpene esters present in Pimelea prostrata (Thymelaeaceae) were isolated and characterized. Of the tigliane types found, prostratin (I) and two autoxidation products thereof proved to be practically non-irritant on the mouse ear. A further new and moderately irritant factor (Pimelea factor P5) of the tigliane type was isolated and characterized as 12-deoxy-5β-hydroxy-13-O-tetradecanoylphorbol-6α,7α-oxide (II a). In addition highly irritant new diterpene esters of the daphnane type, i. e. Pimelea factors P1 (III a) and P4 (III b) and of the new 1α-alkyldaphnane type were isolated, i. e. Pimelea factors P2 (V a), P3 (VI a) and P6 (VII a). The daphnane and 1α-alkyldaphnane types essentially represent the irritant activity of the plant. The structures V a, VI a and VII a represent a new class of irritant and tumor promoting polyfunctional diterpelnes with an intramolecular orthoester function.