Synthesis of inverto-yuehchukene and its 10-(indol-3′-yl) isomer. X-Ray structure of (4aRS,10aRS)-1,1,3-trimethyl-1,2,4a,5,10,10a-hexahydroindene [1,2-b]indol-10-one

Abstract

A total synthesis of inverto-yuehchukene 4 and its 10-(indo-3′-yl) isomer 7 is described. The key tetracyclic ketone intermediate 13 was synthesized by a coupling reaction between 3-indolylzinc reagent and acid chloride 11, followed by Nazarov cyclization of the divinyl ketone 12. The indol-2-yl moiety present in inverto-yuehchukene 4 was introduced by palladium(0)-catalysed cross-coupling between indol-2-ylzinc reagent and the acetate 16.