A total synthesis of (±)-asteriscanolide which features two transition metal-mediated carbocyclic ring forming reactions as key elements of our strategy (Scheme 1) is described. The highly functionalized cyclopentenone 4, the product of a cobalt-mediated Pauson-Khand [2 + 2 + 1] cycloaddition, is the key starting point for the synthesis. Excellent regiocontrol was obtained in the intermolecular Pauson-Khand reaction. Further synthetic manipulations of 4 led to diene 16 which underwent ring-closing metathesis using (PPh3)2Cl2Ru(CHPh) to provide the desired "inside-outside" tricycle 17. Conversion of 17 to 1 was achieved in a minimal number of steps. The synthesis of asteriscanolide has been achieved in 19 steps and 12% overall yield.
我们描述了一种(±)-星雪酮的全合成方法,该方法以两种过渡
金属介导的碳环形成反应为关键步骤(图1)。高度官能化的
环戊烯酮4,是
钴介导的Pauson-Khand [2 + 2 + 1]环加成反应的产物,是合成过程的关键起点。在分子间Pauson-Khand反应中获得了极佳的区域控制。对4的进一步合成操作得到了二烯16,后者通过(PPh3)2Cl2Ru(CHPh)实现的环闭合复分解反应生成了所需的“内外”
三环化合物17。将17转化为1仅需要少数几个步骤。星雪酮的合成在19步反应中完成,总产率为12%。