Enantio- and Diastereoselective Stepwise Cyclization of Polyprenoids Induced by Chiral and Achiral LBAs. A New Entry to (−)-Ambrox, (+)-Podocarpa-8,11,13-triene Diterpenoids, and (−)-Tetracyclic Polyprenoid of Sedimentary Origin
作者:Kazuaki Ishihara、Hideaki Ishibashi、Hisashi Yamamoto
DOI:10.1021/ja0124865
日期:2002.4.1
stepwise cyclization of polyprenoids induced by Lewis acid-assisted chiral Brønsted acids (chiral LBAs) and achiral LBAs is described. In particular, the absolute stereocontrol in the initial cyclization of polyprenoids to form an A-ring induced by chiral LBAs and the importance of the nucleophilicity of the internal terminator in polyprenoids for the relative stereocontrol in subsequent cyclization are
描述了由路易斯酸辅助的手性布朗斯台德酸(手性 LBA)和非手性 LBA 诱导的聚异戊二烯的对映选择性和非对映选择性逐步环化。特别是,证明了在聚异戊二烯初始环化以形成由手性 LBA 诱导的 A 环中的绝对立体控制,以及聚异戊二烯中内部终止子的亲核性对于后续环化中的相对立体控制的重要性。(-)-Ambrox 通过 (E,E)-高法呢基三乙基甲硅烷基醚与氯化锡 (IV) 配位的 (R)-2-(o-氟苄氧基)-2'-羟基-1,1' 的对映选择性环化反应合成-联萘 ((R)-BINOL-o-FBn) 和随后的非对映选择性环化与 CF(3)CO(2)H.SnCl(4) 作为关键步骤。保护 (E, E)-由三乙基甲硅烷基组成的高法呢醇增加了手性 LBA 诱导的环化的对映选择性以及随后环化中的化学产率和非对映选择性。(R)-BINOL-o-FBn.SnCl(4) 还诱导了具有芳基的均(聚异戊二烯基)芳烃的对映选择性环化。通过