ABSTRACT
The phorbol esters belong to the group of natural products based upon the hydrocarbon nucleus known as tigliane. The nature of the phorbol-ester receptor site has been made clearer due to the use of radioactive labeled phorbol compounds, mainly 20-H-phorbol-12, 13-dibutyrate, a relatively simple derivative to synthesize from natural phorbol. Phorbol contains a αβ-unsaturated keto group in ring A of its structure; the presence of this functional group cannot be demonstrated by the normal reagents. This functional group as exhibited by phorbol-12, 13, 20-triacetate undergoes reduction with either sodium borohydride or lithium aluminum hydride. Phorbol ester hydroxyl groups may be selectively alkylated under mild reaction conditions. The synthesis of esters of phorbol from the natural polyol, as isolated by crystallization from the hydrolysis of croton oil, was essential for the structure elucidation of these natural products. Esters of phorbol have been isolated from eight individual species of four genera of the plant family Euphorbiaceae.
