Maria B Mayo Martin and David E Jane

contents

5.1 Introduction 76

5.2 What Is Chirality 76

5.3 The Origin of Stereospecificity in Molecular Recognition 78

5.4 Why Is Stereochemistry Important in Drug Design 79

5.4.1 The Distomer Is Inactive (High ER) 80

5.4.2 Both Enantiomers Have Independent Therapeutic Benefits 80

5.4.3 Distomer Possesses Harmful Effects 81

5.4.4 The Eutomer and the Distomer Have the Opposite

Biological Activity 81

5.4.5 The Racemate Has a Therapeutic Advantage over the

Individual Enantiomers 81

5.4.6 One Enantiomer Is Converted into the Other in the Body 82

5.5 Methods for Obtaining Pure Stereoisomers 83

5.5.1 Resolution of Racemates by Crystallization of Diastereomers 83

5.5.2 Enantioselective Chromatography 84

5.5.2.1 Ligand Exchange 84

5.5.2.2 Crown Ethers 84

5.5.2.3 Pirkle Columns 84

5.5.2.4 Miscellaneous Phases 85

5.5.2.5 Simulated Moving Bed Chromatography 85

5.5.3 Asymmetric Synthesis 85

5.5.3.1 The Chiral Pool 85

5.5.3.2 Stereoselective Synthesis 85

5.5.3.3 The Use of a Chiral Auxiliary 85

5.5.3.4 The Use of Chiral Reagents and Catalysts 86

5.5.3.5 The Use of Enzymes and Whole Organisms 86

5.6 Analytical Methods of Determining Purity of Stereoisomers 87

5.6.1 Nuclear Magnetic Resonance Spectroscopy 87

5.6.2 Gas Chromatography 87

5.6.3 Capillary Electrophoresis 88

5.6.4 Mass Spectrometry 88

5.7 Concluding Remarks 88

Further Readings 88

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