Total Synthesis of (.+-.)-Plumbazeylanone, A Naphthoquinone Trimer from Plumbago zeylanica.
作者:Tetsuya TAKEYA、Manabu KAJIYAMA、Chikara NAKAMURA、Seisho TOBINAGA
DOI:10.1248/cpb.47.209
日期:——
We have investigated the total synthesis of (±)-plumbazeylanone (1), a naphthoquinone trimer based on two different pathways (I) and (II). The synthetic approach based on pathway (I) was not successful. However, the first synthesis of 1 from plumbagin (2a) was achieved by utilizing an unsymmetrical methylene-bridged dimer (20b), with a naphthoquinone unit and a naphthalene unit as a key intermediate, based on pathway (II), in 11 steps with an overall yield of 5.9%. This synthesis features regioselective nucleophilic 1, 2-addition of the naphthyllithium reagent 4a to the C-1 position of naphthoquinone 20b, and the regio- and stereoselective dienone-phenol-type rearrangement of the 1, 2-adduct 21b (1, 2-migration of the naphthyl group to the C3-position on 21b) with 2 N-NaOH.
我们研究了 (±)-plumbazeylanone (1) 的全合成,这是一种基于两种不同途径 (I) 和 (II) 的萘醌三聚体。基于途径(I)的合成方法并不成功。然而,首次从白花丹素 (2a) 合成 1 是通过利用不对称亚甲基桥联二聚体 (20b),以萘醌单元和萘单元作为关键中间体,基于途径 (II),经过 11 个步骤实现的总收益率为5.9%。该合成的特点是萘基锂试剂 4a 与萘醌 20b 的 C-1 位进行区域选择性亲核 1, 2-加成,以及 1, 2-加合物 21b (1, 2-用 2 N-NaOH 将萘基迁移至 21b) 上的 C3 位。