Synthesis of the Cyclopentyl Nucleoside (−)-Neplanocin A fromD-Glucosevia Zirconocene-Mediated Ring Contraction
作者:Leo A. Paquette、Zhenjiao Tian、Christopher K. Seekamp、Tony Wang
DOI:10.1002/hlca.200590099
日期:2005.6
Two approaches for the conversion of d-glucose to (−)-neplanocin A (2), both based on the zirconocene-promoted ring contraction of a vinyl-substituted pyranoside, are herein evaluated (Scheme 1). In the first pathway (Scheme 2), the substrate possesses the α-d-allo configuration (see 6) such that ultimate introduction of the nucleobase would require only an inversion of configuration. However, this
本文评估了两种基于d-葡萄糖转化为(-)-neplanocin A(2)的方法,这两种方法都是基于锆茂促进的乙烯基取代吡喃糖苷的环收缩(方案1)。在第一种途径(方案2),在基板的具有α -D-同种异体配置(参见6),使得所述核碱基的最终介绍将只需要配置的反转。但是,该前体被证明对Cp 2 Zr(= [ZrCl 2(Cp)2 ])无反应,最终结果被认为是在关键中间体中发生实质性非键合空间效应的结果(方案5)。与此相反,C(2)差向异构体(参见7)经历了期望的金属促进的转化为对映体纯的多官能环戊烷(见5在方案3)。该产物中的取代基以使得可以通过双转化序列(方案4)方便地实现向靶核苷的转化的方式排列。求助于钯(0)催化的烯丙基烷基化没有提供生成2的替代方法。