Page 8 - Chiral Separation Techniques

VIII Contents

2.2.1 Chiral Recognition Mechanisms 26
2.2.2 Multi-modal CSPs 28
2.2.3 Predictability of Enantioselectivity 30
2.2.4 Complementary Separations 30
2.3 Method Development with Glycopeptide CSPs 38
2.3.1 Method Development Protocols 38
2.3.2 Column Coupling Technique 39
2.4 Optimization 44
2.4.1 Effect of Flow Rate and Temperature on Enantiomeric
Separations 44
2.4.2 Optimization of Enantiomeric Separations in the New Polar Organic
Mode 46
2.4.3 Optimization of Enantiomeric Separations in
Reversed Phase 48
2.4.3.1 Effect of Organic Modifier on Enantiomeric Separations 48
2.4.3.2 Effect of Aqueous Buffer on Chiral Separations 51
2.4.4 Optimization of Enantiomeric Separations in Normal
Phase 53
2.5 Concluding Remarks 53
References 54

3 Combinatorial Approaches to Recognition of Chirality:
Preparation and the Use of Materials for the Separation
of Enantiomers 57
Frantisek Svec, Dirk Wulff, Jean M. J. Fréchet

3.1 Introduction 57
3.2 Engineering of a Chrial Separation Medium 58
3.3 Chiral Selectors 59
3.3.1 Design of New Chiral Selectors 61
3.4 In Pursuit of High Selectivity 62
3.5 Acceleration of the Discovery Process 63
3.5.1 Reciprocal Approach 63
3.5.2 Combinatorial Chemistry 64
3.6 Library of Cyclic Oligopeptides as Additives to Background
Electrolyte for Chiral Capillary Electrophoresis 64
3.6.1 Library of Chiral Cyclophanes 68
3.6.2 Modular Synthesis of a Mixed One-Bead – One-Selector
Library 70
3.7 Combinatorial Libraries of Selectors for HPLC 73
3.7.1 On-Bead Solid-Phase Synthesis of Chiral Dipeptides 73
3.7.2 Reciprocal Screening of Parallel Library 80
3.7.3 Reciprocal Screening of Mixed Libraries 85
3.7.4 Library-On-Bead 87