The racemic sesquiterpene isocomene (1) has been synthesized starting from 1,7-octadien-3-one (2) in a stereoselective manner (Scheme 2). In the key step 4 5 the C(7), C(8)-bond was formed by an intramolecular thermal ene reaction. Further elaboration of 5 involved the ring contraction 6 7, the elimination 8 9 and the final olefin isomerization 9 1.
外消旋
倍半萜烯
异丁烯(1)已经以立体选择性的方式从1,7-八二烯-3-酮(2)开始合成(方案2)。在关键步骤4 5中,通过分子内热烯反应形成C(7),C(8)键。5的进一步加工涉及环收缩6 7,消除8 9和最终的烯烃异构化9 1。