Stereoselectivity polyolefin cyclization

Once the structure was known, many syntheses were reported and all of a sudden the literature was loaded with stereoselective methods for olefin synthesis. Although it is only a guess, it is probable that the discovery of Cecropia juvenile hormone (CJH) was responsible (in part) for this burst of activity. Another reason would be the interest in carbocycle synthesis via polyolefin cyclizations (the development of steroid and terpene chemistry) which slightly preceeded the discovery of CJH, We will start by looking at the Trost group synthesis (the first synthesis) of CJH and then examine several other syntheses wherein the focus... 

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 ... 

Stereoselectivity in the synthesis of trisubstituted olefins is necessary for the study of biosynthetic routes to polyisoprenoids, the nonenzymatic cyclization of polyolefinic substrates, and the study of insect hormones. 

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