Both enantiomeric tricyclic enones 2 and 3 serving as the synthetic equivalents of chiral cyclohexadienone and cycloheptadienone have been prepared by lipase-mediated kinetic ester ex-change reaction as the key step. The absolute configuration of the latter has been determined by transformation of the (-)-enantiomer 3 into the known (-)-6-methyl-2-cycloheptenone 16 and the cytotoxic marine natural product (-)-clavularin B 19. However, it has been found that the seven-membered enone 3 exhibits lower diastereoselectivity and less favorable thermal stability than the five-membered and six-membered analogues.
作为手性环
己二烯酮和环庚二烯酮合成等价物的对映体
三环烯酮 2 和 3 都是通过
脂肪酶介导的动力学酯交换反应作为关键步骤制备的。通过将(-)-对映体 3 转化为已知的(-)-6-甲基-2-
环庚烯酮 16 和具有细胞毒性的海洋
天然产物 (-)-clavularin B 19,确定了后者的绝对构型。但研究发现,七元烯酮 3 的非对映选择性较低,热稳定性也不如五元和六元类似物。