Total syntheses of theaspirone (A and B) and vitispirane (A and B) are described. The key step in the syntheses is the palladium(II)-catalyzed intramolecular oxaspirocyclization of diene alcohol 4 to either vitispirane or the allylic alcohol 9. The outcome of the oxaspirocyclization is very much dependent on the solvent employed. In water-acetic acid (4:1) a 1:1 mixture of the diastereomeric alcohols
描述了茶
螺环酮(A和B)和维替斯潘(A和B)的总合成。合成中的关键步骤是
钯(II)催化的二烯醇4分子内氧杂螺环环化为维斯匹烷或
烯丙醇9。氧杂螺环化的结果在很大程度上取决于所用的溶剂。在
水-
乙酸(4:1)中,仅形成非对映异构醇9A和9B的1:1混合物。在具有8当量的强非亲核酸的
水中,获得了维斯匹烷A和B(1:1)。描述了使用LiCl和K(2)CO(3)获得维斯匹林的替代方法。在后一反应中,优先生成替斯匹兰B。通过两个可能的pi-烯丙基复合物5A和5B之间的平衡来解释该结果,