Organic Synthesis With Enzymes In Non Aqueous Media

Closing a gap in the literature, this comprehensive book examines and discusses different non-aqueous systems from organic solvents to ionic liquids for synthetic applications, thus opening the door to new successful methods for biocatalytic reactions. It gathers into one handy source the information otherwise widely spread throughout the literature, combining useful background information with a number of synthetic examples, including industrial scale processes for pharmaceutical and fine chemicals. Extremely well structured, the text introduces the fundamentals of non-aqueous enzymology, before going on to new reaction media and synthetic applications using hydrolases and non-hydrolytic enzymes. The one-stop reference for everyone working in this hot field.

Enzymatic catalysis has gained considerable attention in recent years as an efficient tool in the preparation of natural products, pharmaceuticals, fine chemicals, and food ingredients. The high selectivity and mild reaction con- tions associated with enzymatic transformations have made this approach an attractive alternative in the synthesis of complex bioactive compounds, which are often difficult to obtain by standard chemical routes. However, the maj- ity of organic compounds are not very soluble in water, which was traditi- ally perceived as the only suitable reaction medium for the application of biocatalysts. The realization that most enzymes can function perfectly well under nearly anhydrous conditions and, in addition, display a number of useful properties, e. g. , highly enhanced stability and different selectivity, has d- matically widened the scope of their application to the organic synthesis. Another great attraction of using organic solvents rather than water as a reaction solvent is the ability to perform synthetic transformations with re- tively inexpensive hydrolytic enzymes. It is worth reminding the reader that in vivo, the synthetic and hydrolytic pathways are catalyzed by different enzymes. However, elimination of water from the reaction mixture enables the “reversal” of hydrolytic enzymes and thus avoids the use of the expensive cofactors or activated substrates that are required for their synthetic count- parts.

Extending the range of enzymatic catalysis by using non-aqueous media has now developed into a powerful approach in biochemistry and biotechnology. One peculiar feature which distinguishes it from the conventional enzymology (carried out in aqueous buffers) is that the awareness of different parameters that control and influence the behaviour of enzymes in such environments has emerged rather slowly. Science is about being able to repeat what somebody else has done. Absence of knowledge about such well-defined parameters/fac tors has sometimes made some workers rather cautious and diffident about using this approach in their laboratories. But for this, non-aqueous enzymol ogy would be more widely practised. It is these thoughts that made me feel that the availability of some well-defined protocols for various applications invol ving enzymes in non-aqueous environments would further catalyze the growth of this area. Hence this book, in which each chapter has some protocols in a specific area. The protocols are preceded by brief background material. The early chapters, which are of general importance, concern control of water ac tivity and stabilization via immobilization. Some subsequent chapters provide the protocols for transformations involving lipids and carbohydrates, peptide synthesis, and preparation of chiral compounds. The disproportionate focus on lipases is not a coincidence; this class of enzymes has been used more often than others in non-aqueous enzymology.

The outlook of organic synthesis has changed many times during its tractable history. The initial focus on the synthesis of substances typical of living matter, exemplified by the first examples of organic chemistry through the synthesis of urea from inorganic substances by Liebig, was accepted as the birth of organic chemistry, and thus also of organic synthesis. Although the early developments in organic synthesis closely followed the pursuit of molecules typical in nature, towards the end of the 19th century, societal pressures placed higher demands on chemical methods appropriate for the emerging age of industrialization. This led to vast amounts of information being generated through the discovery of synthetic reactions, spectroscopic techniques and reaction mechanisms. The basic organic functional group transformations were discovered and improved during the early part of this century. Reaction mechanisms were elucidated at a growing pace, and extremely powerful spectroscopic tools, such as infrared, nuclear magnetic resonance and mass spectrometry were introduced as everyday tools for a practising organic chemist. By the 1950s, many practitioners were ready to agree that almost every molecule could be syn thesized. Some difficult stereochemical problems were exceptions; for example Woodward concluded that erythromycin was a "hopelessly complex target". This frustration led to a hectic phase of development of new and increasingly more ingenious protecting group strategies and functional group transformations, and also saw the emergence of asymmetric synthesis.

This book covers the most recent development of enzymatic organic synthesis, with particular focus on the use of isolated enzymes. It is organized into one introductory chapter dealing with the characteristics of enzymes as catalysts, and five chapters dealing with different types of chemical transformations. Methods for enzyme immobilization and stabilizaton, the use of enzymes in extreme environments, and the alteration of enzyme properties by chemical modification and site-directed mutagenesis for synthetic purposes are covered.

The synergy between synthetic biology and biocatalysis is emerging as an important trend for future sustainable processes. This book reviews all modern and novel techniques successfully implemented in biocatalysis, in an effort to provide better performing enzymatic systems and novel biosynthetic routes to (non-)natural products. This includes the use of molecular techniques in protein design and engineering, construction of artificial metabolic pathways, and application of computational methods for enzyme discovery and design. Stress is placed on current ‘hot’ topics in biocatalysis, where recent advances in research are defining new grounds in enzyme-catalyzed processes. With contributions from leading academics around the world, this book makes a ground-breaking contribution to this progressive field and is essential reading for graduates and researchers investigating (bio)catalysis, enzyme engineering, chemical biology, and synthetic biology.

This reference book originates from the interdisciplinary research cooperation between academia and industry. In three distinct parts, latest results from basic research on stable enzymes are explained and brought into context with possible industrial applications. Downstream processing technology as well as biocatalytic and biotechnological production processes from global players display the enormous potential of biocatalysts. Application of "extreme" reaction conditions (i.e. unconventional, such as high temperature, pressure, and pH value) - biocatalysts are normally used within a well defined process window - leads to novel synthetic effects. Both novel enzyme systems and the synthetic routes in which they can be applied are made accessible to the reader. In addition, the complementary innovative process technology under unconventional conditions is highlighted by latest examples from biotech industry.

This volume addresses the key topics: nonaqueous enzymology in general and protein design for organic solvents in particular, and enzymatic synthesis of carbon-carbon bonds, novel oligosaccharides, and modified steroids. It is a valuable source to experienced as well as potential users of enzymes.