Synthesis of (+)- and (−)-ferruginol via asymmetric cyclization of a polyene

Abstract

Stereoselectivity of modified polyenes which have a terminal benzene ring was found to be dependent on the size of substituent on the adjacent asymmetric carbon to the terminal benzene ring of the polyenes. (R)-(+)-2′-Hydroxy-1,1′-binaphthyl-2-yl (2R)-2-(4-methoxyphenyl)-5,9-dimethyldeca-4,8-dienoate gave (R)-(+)-2′-hydroxy-1,1′-binaphthyl-2-yl (4aS,9R,10aS)-1,2,3,4,4a,9,10,10a-octahydro-6-methoxy-1,1,4a-trimethylphenanthene-9-carboxylate stereoselectively by treatment with BF₃·Et₂O in nitromethane. The products were elaborated to (+)-ferruginol 1. (−)-Ferruginol 2 and (±)-ferruginol 3 were also synthesized via a similar synthetic route.