New general approach to the synthesis of yuehchukene analogues. Stereoselective synthesis of 9,10-dihydro-7α,9-didemethylyuehchukene. X-Ray molecular structure of 6β-(indol-3′-yl)-7β-methyl-5-phenylsulphonyl-5,6,6aβ,7,8,9,10,10aβ-octahydroindeno[2,1-b]indole

Abstract

A versatile synthetic strategy for the syntheses of the yuehchukene analogues 6β-(indol-3′-yl)-7β-methyl-5,6,6aβ,7,8,9,10,10aβ-octahydroindeno[2,1-b] indole and 7β-methyl-6β-(2′-methylindol-3′-yl)-5,6,6aβ,7,8,9,10,10aβ-octahydroindeno[2,1-b]indole is described. The key reactions involve trapping of the vinyllithium derivative 6-methylcyclohex-1 -enyllithium, generated from the trisylhydrazone of 2-methylcyclohexanone, with indole-2-carbaldehyde, and Nazarov cyclization of the α,β-unsaturated 2-acylindole 6-methylcyclohex-1-enyl N-phenylsulphonylindol-2-yl ketone.