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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.
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.
The Organic Chemistry of Enzyme-Catalyzed Reactions is not a book on enzymes, but rather a book on the general mechanisms involved in chemical reactions involving enzymes. An enzyme is a protein molecule in a plant or animal that causes specific reactions without itself being permanently altered or destroyed. This is a revised edition of a very successful book, which appeals to both academic and industrial markets. Illustrates the organic mechanism associated with each enzyme-catalyzed reaction Makes the connection between organic reaction mechanisms and enzyme mechanisms Compiles the latest information about molecular mechanisms of enzyme reactions Accompanied by clearly drawn structures, schemes, and figures Includes an extensive bibliography on enzyme mechanisms covering the last 30 years Explains how enzymes can accelerate the rates of chemical reactions with high specificity Provides approaches to the design of inhibitors of enzyme-catalyzed reactions Categorizes the cofactors that are appropriate for catalyzing different classes of reactions Shows how chemical enzyme models are used for mechanistic studies Describes catalytic antibody design and mechanism Includes problem sets and solutions for each chapter Written in an informal and didactic style
Books dealing with the mechanisms of enzymatic reactions were written a generation ago. They included volumes entitled Bioorganic Mechanisms, I and II by T.C. Bruice and S.J. Benkovic, published in 1965, the volume entitled Catalysis in Chemistry and Enzymology by W.P. Jencks in 1969, and the volume entitled Enzymatic Reaction Mechanisms by C.T. Walsh in 1979. The Walsh book was based on the course taught by W.P. Jencks and R.H. Abeles at Brandeis University in the 1960's and 1970's. By the late 1970's, much more could be included about the structures of enzymes and the kinetics and mechanisms of enzymatic reactions themselves, and less emphasis was placed on chemical models. Walshs book was widely used in courses on enzymatic mechanisms for many years. Much has happened in the field of mechanistic enzymology in the past 15 to 20 years. Walshs book is both out-of-date and out-of-focus in todays world of enzymatic mechanisms. There is no longer a single volume or a small collection of volumes to which students can be directed to obtain a clear understanding of the state of knowledge regarding the chemicals mechanisms by which enzymes catalyze biological reactions. There is no single volume to which medicinal chemists and biotechnologists can refer on the subject of enzymatic mechanisms. Practitioners in the field have recognized a need for a new book on enzymatic mechanisms for more than ten years, and several, including Walsh, have considered undertaking to modernize Walshs book. However, these good intentions have been abandoned for one reason or another. The great size of the knowledge base in mechanistic enzymology has been a deterrent. It seems too large a subject for a single author, and it is difficult for several authors to coordinate their work to mutual satisfaction. This text by Perry A. Frey and Adrian D. Hegeman accomplishes this feat, producing the long-awaited replacement for Walshs classic text.
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.
Transformations using enzymes have been extensively investigated in the last two decades and the results promise great potential for this growing field, especially in the area of synthetic organic chemistry mainly due to of its many advantages. Accordingly, this book has attempted to bring out the advantages of using enzymes involving complex underivatized and unprotected substrates in non-polar media under homogenous and heterogeneous reaction conditions. Merits and demerits of using enzymes in terms of yields and selectivity/specificity are presented without any prejudice. Almost all the reactions dealt with are from the author’s laboratory comprising diverse substrates, and the catalysis involves two important hydrolyzing enzymes, extensively examined for the reverse reactions. Thus, esterification involving lipses and glycosylation involving glycosidases were investigated with respect to various strategies like optimization of reaction conditions, response surface methodology and kinetics, carrying out reactions under solvent, non-solvent and super critical carbon dioxide conditions. In short, the work presented is to ensure the comprehension of the problems faced by the researchers in this area so as to work out further efficient strategies for carrying out enzymatic transformations in the laboratory successfully with better yields and specificity.
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.
From a biotechnological perspective there are many potential advantages of employing enzymes in organic as opposed to aqueous media. To that end, we have concluded an initial three-year research program in the area of enzymatic catalysis in organic solvents. Our studies have focused on the effect of protein hydration on subtilisins BPN' and Carlsberg in nonaqueous media. Investigations on protein engineered mutants, catalyst engineering studies, and structural studies, primarily employing EPR spectroscopy, have revealed fundamental information on the role of water, the the nature of enzyme structure, and the effects of solvents on the catalytic activity in organic solvents. This study has also resulted in several rational methods to dramatically improve enzyme activity under anhydrous conditions. Catalytic activities in organic solvents can now be expressed at levels similar to that in water--this is a major advance in the field of nonaqueous enzymology. (jg).