Synthesis of (6S,6aS,7R,10S,10aR)-6-(indol-3-yl)-7,11,11-trimethyl-5,6,6a,7,8,9,10,10a-octahydro-7,10-methanoindeno[2,1-b]indole and its enantiomer: absolute configuration of active yuehchukene

Abstract

Efficient synthesis of the title compound and its R-enantiomer from readily available (1S)–(–)-camphor or (1R)-(+)-camphor, respectively, is described. Stable conformations of the title compounds and yuehchukene were compared by employment of the MM2 force field for energy calculation and minimization. Since yuehchukene occurs in Nature in racemic form, a bioassay study of enantiomerically pure S- and R-enantiomer of the title compound would provide an indication as to which enantiomer of yuehchukene is responsible for its activity. Results of the study led to the conclusion that the enantiomer of yuehchukene which is biologically active should possess the R-absolute configuration at C-6.