Triterpenes asymmetric epoxidation

Squalene 2,3-oxide has been proposed to account for a vast array of polycyclic triterpenes in natureJ The synthesis of 6-amyrin by van Tamelen and his associates mimics the biological cyclization process, featuring the stereoselective generation of five asymmetric centres during a polyolefinic cyclization of the terminal epoxide Preparation of DIE Component ... 

Triterpenes are much rarer than sesquiterpenes or diterpenes, and can be divided into two distinct groups. The first group comprises squalene and its three possible epoxides which are also characterized by having all their asymmetric carbons with the configuration (S) 2,3(S), 6(S),7(S), and 10(S),ll(S)-epoxysqualene. These four substances were isolated from a single species, Caulerpa prol era (De Napoli et al., 1980, 1982). 

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