Racemisation of drug enantiomers by benzylic proton abstraction at physiological pH

Chirality. 1994;6(5):400-4. doi: 10.1002/chir.530060507.

Abstract

The enantiomers of the aromatase inhibitors 3-(4-aminophenyl)-pyrrolidine-2,5-dione (WSP-3, II), its N-pentyl derivative (III), and the antifungal econazole (IV), all possessing a benzylic proton at the chiral centre, are rapidly racemised in vitro in phosphate buffer (0.01 M) at pH 7.4 and 23 degrees C with t 1/2 values of 7, 6, and 5 h respectively. In vivo studies in rats show that (+)-econazole is racemised after intraperitoneal injection with t 1/2 = 1.24h. The enantiomers of the antifungal 1-[(benzofuran-2-yl)-4-chlorophenylmethyl] imidazole (V) were stable at pH 7.4, attributable to steric hindrance to carbanion formation in the racemisation step.

MeSH terms

  • Aniline Compounds / chemistry*
  • Aniline Compounds / isolation & purification
  • Aniline Compounds / pharmacology
  • Animals
  • Aromatase Inhibitors
  • Buffers
  • Econazole / chemistry*
  • Econazole / isolation & purification
  • Econazole / pharmacology
  • Half-Life
  • Hydrogen-Ion Concentration
  • Kinetics
  • Phosphates
  • Protons
  • Pyrrolidinones / chemistry*
  • Pyrrolidinones / isolation & purification
  • Pyrrolidinones / pharmacology
  • Rats
  • Stereoisomerism
  • Succinimides / chemistry*
  • Succinimides / isolation & purification
  • Succinimides / pharmacology

Substances

  • 1-pentyl-3-(4-aminophenyl)pyrrolidine-2,5-dione
  • Aniline Compounds
  • Aromatase Inhibitors
  • Buffers
  • Phosphates
  • Protons
  • Pyrrolidinones
  • Succinimides
  • 3-(4'-aminophenyl)pyrrolidine-2,5-dione
  • Econazole