Triterpenes pentacyclic, squalene-derived

Matsuo Y, Suzuki M, Masuda M (1995) Enshuol, a Novel Squalene-Derived Pentacyclic Triterpene Alcohol from a New Species of the Red Algal Genus Laurencia. Chem Lett 1043... 

B Formation of Tetracyclic and Pentacyclic Triterpenes from Squalene Epoxide. In most microorganisms and in plants and animals the cyclic triterpenes are derived from squalene-2,3-epoxide, which is formed from squalene by a monooxygenase (C 2.6.5). The action of different, squalene epoxide cyclases results in the formation of different types of cyclic triterpenes. 

The steroid euphol as well as the pentacyclic triterpenes may be derived from squalene epoxide in chair-chair-chair-boat-unfolded conformation (Figs. 116 and 117). 

Matsuo, Y, Suzuki, M, and Masuda, M. (1995) Enshuol, a novel squalene-derived pentacyclic triterpene alcohol from a new species of the red alga Laurencia. Chem. Lett., 24,1043-1044. 

Several pentacyclic triterpenes found in ferns also appear to be formed from squalene (1), but not via the intermediacy of the 2,3-epoxide (2) (Fig. 23.4). Compounds, such as fer-nane (16), are found in several ferns (Goodwin, 1973). 24-Ethoxyhopane (17) has been reported from the fern Onoclea neriifolia. Although these triterpenes apparently are distributed widely in ferns, triterpenes derived from condensation of squalene 2,3-oxide frequently co-occur with them. 

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