Diterpene Synthesis. IV. Synthesis of Some Octahydrophenanthrenes and a Contribution to the Mechanisms of Cyclialkylations

Abstract

The cis octahydrophenanthrene (3), a product of the acid-catalysed cyclialkylation of alcohol (1), has been synthesized. Various analogues having cis A/B stereochemistry have also been isolated from cyclization reactions; in these cases there is no rearrangement of the carbon skeleton, as shown by isotopic labelling. Variable temperature n.m.r. studies have been used to define the conformations of some of the cis octahydrophenanthrenes. The mechanisms of cyclialkylations leading to octahydrophenanthrenes can now be clarified.