Perhydrophenanthrene skeleton

This example aside, the utility of the electrohydrocyclization reaction in the assembly of natural products remains essentially untapped. The reason for this observation is not entirely clear. Consider, for example, the rapid and efficient construction of the perhydrophenanthrene skeleton as exemplified by the conversion illustrated below [18]. The reaction is stereospecific, leading to the trans-anti-trans ring fused adduct 13 in a 65 to 72% yield. It takes little thought to imagine the application of this powerful transformation to the synthesis of steroids. Yet, this opportunity has not b n realized. 

A further prospect for these derivatives originates with the substituted enones (161) and (162) (Scheme 38) which are expected to give the Diels-Alder adducts (194) and (198) respectively. The latter is of particular interest since conversion of the pyranose into a cyclohexane ring (see for example Schemes 35—37), would afford the decalone (199) cis or trans) which has the proper absolute stereochemistry for the A and B rings of the majority of terpenes. Furthermore, the functionalization of (199) makes it a synthon of the perhydrophenanthrene (200) and perhydro-anthracene (201) skeletons. 

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