The synthesis of vicinal trimethoxyoctahydrophenanthrene derivatives

Abstract

Diels–Alder condensation of 3,4-dihydro-5,6,7-trimethoxy-1-vinylnaphthalene with methyl acrylate gave two isomeric hexahydro-6,7,8-trimethoxyphenanthrene-2α-carboxylic acids (2) and (3). The acid (2) was readily isomerized under acidic conditions to the acid (3). Both compounds (2) and (3) gave the same octahydrophenanthrenecarboxylic acid (4) on reduction with a limited quantity of sodium and liquid ammonia. Reduction of either acid (2) or (3) with excess of sodium and liquid ammonia caused loss of the 7-methoxy-group.