Synthesis of (±)‐Kempa‐6,8‐dien‐3‐ol (=(2a<i>RS</i>,3<i>SR</i>,4a<i>SR</i>,7<i>RS</i>,7a<i>SR</i>,10b<i>SR</i>,10c<i>SR</i>)‐2,2a,3,4,4a,5,6,7,7a,8,10b,10c‐Dodecahydro‐2a,7,10,10c‐tetramethylnaphth[2,18‐<i>cde</i>]azulen‐3‐ol)

Abstract

Abstract The synthesis of kempa‐6,8‐dien‐3 β ‐ol ( 4a ), as a synthetic leading model of the natural product 4b , was carried out starting from intermediate 12 , the synthetic route of which has been developed previously ( Scheme 1 ). The conversion of 12 to the model compound 4a involved the elaboration of three structure modifications by three processes, Tasks A, B , and C (see Scheme 2 ). Task A was achieved by epoxy‐ring opening of 41 with Me 3 SiCl ( Scheme 9 ), and Task B being performed by oxidation at the 13‐position, followed by hydrogenation, and then epimerization ( Schemes 4 and 5 ). The removal of the 2‐OH group from 12 ( Task C ) was achieved via 30b according to Scheme 6 , whereby 30b was formed exclusively from 30a / 31a 1 : 1 ( Scheme 7 ). In addition, some useful reactions from the synthetic viewpoint were developed during the course of the present experiments.