Enantiomerenreine Pyrrolidin‐Derivate aus <i>trans</i>‐4‐Hydroxy‐<scp>L</scp>‐prolin durch elektrochemische oxidative Decarboxylierung und Titantetrachlorid‐vermittelte Umsetzung mit Nukleophilen

Abstract

Enantiomerically Pure Pyrrolidine Derivatives from trans ‐4‐Hydroxy‐ L ‐proline by Electrochemical Oxidative Decarboxylation and Titanium‐Tetrachloride‐Mediated Reaction with Nucleophiles Preparative electrolysis of N ‐methoxycarbonyl‐ O ‐[( t ‐butyl)dimethylsilyl]hydroxyproline 4 in MeOH leads to substitution of the COOH by a MeO group (oxidative decarboxylation). The mixture 5 of the two diastereoisomers ( ca 1:1) thus obtained was reacted in CH 2 Cl 2 with nucleophilic silylated compounds (such as allylsilane, silyl cyanide and 1‐phenyl‐1‐silyloxyethane) or with trimethyl phosphite in the presence of TiCl 4 to give 2‐allyl‐, 2‐cyano‐, 2‐(2‐oxo‐2‐phenylethyl)‐ and 2‐phosphono‐substituted hydroxypyrrolidines, respectively, with high diastereoselectivities (≥ 90%, products 6‐12 ). The configuration of two of the products ( 6/7 and 8/9 ) was shown to be cis .