Asymmetric synthesis of 1,2,3-trisubstituted cyclopentanes and cyclohexanes as key components of substance p antagonists

J Org Chem. 2002 Aug 23;67(17):5993-6000. doi: 10.1021/jo025883m.

Abstract

An efficient asymmetric synthesis of 1,2,3-trisubstituted cyclopentanes and cyclohexanes is described. Three methods were developed for the preparation of the 2,3-disubstituted cyclopentenones and cyclohexenones, which are key achiral building blocks. These intermediates are reduced catalytically with (R)-2-methyloxazaborolidine in high yield (82-98%) and excellent ee (89-96%). Directed reduction of the chiral allylic alcohols using Red-Al gives exclusively the 1,2-anti stereochemistry (>99:1). Epimerization of the ester center followed by saponification/crystallization affords the desired hydroxyacids in good yield (65-70%) and in high enantiomeric excess (>99%).

MeSH terms

  • Catalysis
  • Combinatorial Chemistry Techniques / methods*
  • Cyclohexanes / chemical synthesis*
  • Cyclopentanes / chemical synthesis*
  • Molecular Conformation
  • Molecular Structure
  • Stereoisomerism
  • Substance P / antagonists & inhibitors*

Substances

  • Cyclohexanes
  • Cyclopentanes
  • Substance P