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Keywords:

  • absolute configuration;
  • conformation;
  • malathion;
  • VCD spectroscopy;
  • conformational code;
  • DFT calculation;
  • MM calculation;
  • conformome

Abstract

The absolute configuration and solution conformation of (R)-(+)-malathion were determined by using vibrational circular dichroism spectroscopy and a fragment-conformational search with a recently published conformational code. The determination of molecular stereochemistry was carried out without a conformational search using molecular mechanics calculations. Density functional theory calculations of the fragments of (R)-malathion, ethyl propionate, (R)-ethyl 2-(methylthio)propanoate, (R)-diethyl 2-(methylthio)succinate, and O,O,S-trimethyl phosphorodithioate were carried out, and the principal conformational features of the fragments were profiled. This fragment-conformational search reduces the time needed for the selection of the predominant conformations for (R)-malathion and significantly improves the accuracy of the determination of absolute configuration. Chirality 21:E172–E180, 2009. © 2009 Wiley-Liss, Inc.