Synthesis of (+-)-Kempa-6,8-dien-3-ol (=(2aRS,3SR,4aSR,7RS,7aSR,10bSR,10cSR)-2,2a,3,4,4a,5,6,7,7a,8,10b,20c-Dodecahydro-2a,7,10,10c-tetramethylnaphth[2,18-cde]azulen-3-ol))

摘要

The synthesis of kempa-6,8-dien-3beta-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_3SiCl (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.