The asymmetric syntheses of 25 and 29, which constitutes the C(3)–C(15) segment of the stereochemically complex ansa chain of (+)-macbecin I (1) and herbimycin A (2), respectively, have been achieved. The approach features the furan-hydropyranone transformation 9→10 followed by stereoselective introduction of substituents onto the conformationally-biased hydropyran ring of 10 to give 17. Extension
已实现25和29的不对称合成,分别构成(+)-macbecin I(1)和除草霉素A(2)的立体
化学复杂ansa链的C(3)–C(15)段。该方法的特征是
呋喃-氢
吡喃酮转化9→10,然后将取代基立体选择性地引入构象偏向的氢
吡喃环10上,得到17。侧链17的延伸导致枢轴中间件22,该中间件被细化为25和29。25羧基末端的重新官能化提供了26,通过立体选择性地将芳基
锂加到内醇30中转化为32。32的结构通过将其转化为34来建立,该结构是Baker 1的总合成中的高级中间体,从而完成了光学纯(+)-macbecin I(1)的形式合成。