CONFORMATIONALLY SELECTIVE TRANSANNULAR CYCLIZATION OF HUMULENE 9,10-EPOXIDE. SYNTHESIS OF THE TWO SKELETALLY DIFFERENT CYCLOHUMULANOIDS: DL-BICYCLOHUMULENONE AND DL-AFRICANOL

Article abstract of DOI:10.1016/0040-4039(80)80152-3

Two cyclohumulanoids, dl-bicyclohumulenone (4) and dl-africanol (7) were synthetized through newly developed conformationally selective transannular cyclization of humulene 9,10-epoxide (2).The epoxide 2 was converted to a bicyclohumulenediol diacetate 3a in 70percent yield by treatment with BF3.Et2O-Ac2O, while treatment of 2 with trimethylsilyl trifluoromethansulfonate gave an africen-ol (5a and 5b) in 80percent yield.The two intermediates 3a and 5a furnished the natural products 4 and 7 in 30 and 8 percent yield from 2 respectively.