Oligo‐ and macrocyclic diterpenes in thymelaeaceae and euphorbiaceae occurring and utilized in yunnan (Southwest China) 4. Tigliane type diterpene esters (phorbol–12,13‐diesters) from Wikstroemia canescens

From a methanol extract of the roots of Wikstroemia canescens (Wall) Meisen the hitherto unknown Wikstroemia factors C1 and C2 were isolated by means of a Craig distribution followed by TLC. They were identified as the tigliane type phorbol–12‐benzoate–13‐decanoate (C2) and the corresponding–13‐3E, 5E‐decadienoate) (C1). On the mouse ear Wikstroemia factor C1 showed irritant activity comparable to that of the standard irritant phorbol ester 12‐O‐tetradecanoylphorbol–13‐acetate. Wikstroemia factor C2, not assayed for irritancy, may be expected to be about as active as C1.