Chirality

Les hypotheses, n'en deplaise a mon contradicteur, sont l'ame des progres de la science. Louis Pasteur The concept of chirality, established 100 years ago, plays an im portant role in almost all domains and dimensions of our recent scientific view of life. Chiral properties can be found in fundamen tal nuclear particles, in molecules, and in the macroscopic world of living nature (plants and animals) and inanimate nature (crystals). In particular, chirality, or more precisely chiral excess, is evident in human beings. For example, the expected symmetry of the hands turns out to be functionally non-existent. Consequently chirality occurs in the technical sphere, where screws are the best-known examples, since most of them are made for right-handed people. Chirality is not confined to static objects but influences processes such as chemical reactions. The occurrence of chiral objects on different dimensional scales has been treated in the past in mutually independent frameworks. There were, however, two remarkable events from which the conclu sion can be drawn that the appearance of chirality in various fields has a common cause. On the one hand, physicists found evidence that the well-known biomolecular homochirality can be traced back to the chirality of weak bosons. At the same time, on the other hand, the so-called thalidomide tragedy occurred when thalido mide molecules of a certain chirality, taken by pregnant women, caused deformed children.

The phenomenon of chirality occurs in many disciplines of natural sciences, such as elementary particle physics, chemistry of molecules, biopolymers and crystals, pharmacology, biology (snails, winding plants), and medicine (handedness). This book gives for the first time an interdisciplinary comprehensive treatment of chirality. Ten well-known scientists describe the present state of the art in different fields in introductory review articles without going into detail.

1 Parity Violation in Atomic Physics.- 1.1 Introduction.- 1.2 Parity.- 1.3 Elementary Particles and Forces.- 1.3.1 Leptons and Quarks.- 1.3.2 Forces and Interactions.- 1.3.3 Spin and Helicity (Chirality).- 1.3.4 Unified Theory of Weak and Electromagnetic Interactions ("Standard Model").- 1.4 Parity-Violating Effects in Atoms.- 1.4.1 Phenomenology.- 1.4.2 Experiments.- 1.5 References.- 2 Theories on the Origin of Biomolecular Homochirality.- 2.1 Introduction.- 2.2 Observability of Chiral Molecular Structures.- 2.3 Kinetic Models for Unstable Equilibrium.- 2.4 Kinetic Models with Instrinsic Asymmetry.- 2.5 Parity-Violating Energy Differences Between Enantiomers.- 2.6 Homochirality from Stochastic Equations.- 2.7 References.- 3 Chirality and Group Theory.- 3.1 Introduction.- 3.2 The Principle of Pairwise Interactions.- 3.3 The Theory of Chirality Functions.- 3.4 The Approximation Methods.- 3.5 Determining the Lowest-Degree Chirality Polynomials.- 3.6 Qualitative Completeness and Supercompleteness.- 3.7 Counting Enantiomeric Pairs.- 3.8 References.- 4 Helicity of Molecules - Different Definitions and Application to Circular Dichroism.- 4.1 Introduction.- 4.2 The Ideal Finite Helix.- 4.3 Real Molecules or Parts of Them, Fractions of a Helix.- 4.4 Rules.- 4.4.1 The Torsional-Angle-Rule (CIP).- 4.4.2 The IUPAC-Axis-Tangent-Rule.- 4.4.3 The Two-Tangent Rule.- 4.4.4 The Spade-Product Rule.- 4.4.5 The Spiral-Staircase-Rule.- 4.5 Some Applications.- 4.6 Summary.- 4.7 References.- 5 Anomalous Dispersion of X-Rays and the Determination of the Handedness of Chiral Molecules.- 5.1 Introduction.- 5.2 "Normal" X-Ray Diffraction.- 5.2.1 Scattering from a Crystal.- 5.2.2 Friedel's Law and When It Breaks Down.- 5.2.3 Physical Origin of Anomalous Scattering.- 5.3 Past, Presence and Future Use of Anomalous Scattering.- 5.3.1 Outlook.- 5.4 References.- 6 Chirality in Organic Synthesis - The Use of Biocatalysts.- 6.1 Chirality in Organic Chemistry and Biochemistry.- 6.1.1 Explanation of Basic Terms.- 6.1.2 Comparison of Properties: Enantiomers and Diastereomers.- 6.1.3 The Importance of Enantiomeric Purity.- 6.1.4 Methods of Obtaining Enantionerically Pure Chiral Compounds.- 6.2 Biocatalysts in Organic Chemistry - General Remarks.- 6.2.1 Enzymes.- 6.2.2 Whole Cell Systems.- 6.2.3 Types of Selectivities Achieved.- 6.3 Enzymes.- 6.3.1 Classes and Nomenclature.- 6.3.2 Properties and Stabilities.- 6.3.3 Coenzymes.- 6.3.4 Enzyme Mechanisms.- 6.3.5 Active Site and Enzyme Models.- 6.4 Use of Whole Cell Systems.- 6.4.1 Principles.- 6.4.2 Application to Unnatural Substrates.- 6.5 Application of Biocatalytic Hydrolysis.- 6.5.1 General Remarks.- 6.5.2 Resolution of Racemates.- 6.5.3 Asymmetrization of Prochiral and meso-Compounds.- 6.5.4 Selective Protection and Deprotection.- 6.5.5 Mild Conditions.- 6.6 Reduction and Oxidation Using Biocatalysts.- 6.6.1 Introduction.- 6.6.2 Enzymatic Cofactor Recycling.- 6.6.3 Enantioface Differentiation in Reduction of Ketones.- 6.6.4 Oxidation of Ketones.- 6.6.5 Hydroxylation of Nonactivated Carbon Atoms.- 6.6.6 Other Oxidations.- 6.7 Further Applications.- 6.7.1 Use of Organic Solvents, Transesterification.- 6.7.2 Lyase-Catalyzed Additions to Double Bonds.- 6.7.3 C-C Bond Formation and Cleavage.- 6.7.4 Transferases.- 6.8 Special Techniques and Novel Developments.- 6.8.1 Immobilization Techniques.- 6.8.2 Artificial and Modified Enzymes, Enzyme Mimics.- 6.8.3 Catalytic Antibodies.- 6.9 Comparison of Methods and Outlook.- 6.9.1 Advantages and Disadvantages of Biocatalysts.- 6.9.2 Future Developments and Trends.- 6.10 References.- 7 Preparation of Homochiral Organic Compounds.- 7.1 Introduction.- 7.2 Separation Techniques.- 7.3 Homochiral Building Blocks from Natural Products.- 7.4 Auxiliary Modified Substrates.- 7.5 Homochiral Reagents.- 7.6 Homochiral Catalysts.- 7.7 References.- 8 Transition Metal Chemistry and Optical Activity - Werner-Type Complexes, Organometallic Compounds, Enantioselective Catalysis.- 8.1 Werner-Type Complexes.- 8.2 Organometallic Compounds.- 8.3 Enantioselective Catalysis with Optically Active Transition Compounds.- 8.4 References.- 9 Strategies for Liquid Chromatographic Resolution of Enantiomers.- 9.1 Background of Basic Chromatorgraphic Terms.- 9.2 Strategies to Separate Enantiomers by Chromatographic Techniques.- 9.3 Thermodynamic and Kinetic Considerations for Chromatographic Enantioseparation.- 9.4 Enantioselective Liquid Chromatography.- 9.5 Direct Enantioseparation by Liquid Chromatography.- 9.6 Chiral Phases Using Polymers as Chiral Selectors.- 9.7 Chiral Stationary Phases Using Proteins (Polypeptides) as Chiral Selectors.- 9.8 Chiral Stationary Phases Based on Synthetic Chiral Polymers.- 9.9 Chiral Stationary Phases Based on "Brush Type" Immobilization of Small Selector Molecules.- 9.10 Final Remarks on Brush Type and Inclusion Type CSPs.- 9.11 Indirect Enantioseparation.- 9.12 Final Remarks.- 9.13 References.- 10 The Nucleoproteinic System.- 10.1 Introduction.- 10.2 The Chiral Message.- 10.3 The Evolution of the Chiral Amphiphilic Patterns.- 10.3.1 Darwinian Selection for Chiral Information-Processing Patterns.- 10.3.2 Basal Geometries of Chiral Nucleoproteinic Constituents.- 10.3.3 The DNA-RNA-Protein Triad.- 10.4 Stabilization Within the Dynamics.- 10.5 Outlook.- 10.6 References.