In our studies towards the total synthesis of solanoeclepin A, a natural hatching agent of potato cyst nematodes, three analogues containing the tetracyclic left-handed substructure have been synthesised. First, the synthesis of the parent tetracycle 2 in enantiopure form is reported. Key steps are (1) chromium-mediated coupling of aldehyde 5 (see preceding paper in this issue) and vinyl triflate 6 to furnish an α,β-unsaturated lactone, which was transformed into triene 4 in six-steps, (2) ring-closing metathesis of 4 to tetracycle 3 and (3) oxidative functionalisation of the least substituted double bond of 3 to provide the fully functionalised tetracyclic left-handed substructure
of solanoeclepin A. The methodology developed was successfully applied in the synthesis of two more elaborate solanoeclepin A analogues 9 and 11. Both compounds, prepared as mixtures of diastereomers, showed promising biological activity in hatching activity tests.
在我们对马铃薯胞囊线虫
天然孵化剂solanoeclepin A的全合成研究中,已经合成了三个含有四环左手子结构的类似物。首先,报道了母四环2的手性纯粹形式的合成。关键步骤是(1)通过
铬介导的醛5(见本期前文)和
乙烯基三
氟磺酸盐6的耦合,得到α,β-不饱和内
酯,经过六步转变为
三烯4,(2)4的环闭合
金属转移反应形成四环3,以及(3)3上最少取代的双键的
氧化功能化,得到solanoeclepin A的完全功能化的四环左手子结构。所开发的方法成功地应用于合成两个更复杂的solanoeclepin A类似物9和11。这两个化合物均以非对映异构体混合物形式制备,并在孵化活性测试中显示出有希望的
生物活性。