-APPLICATION OF ENZYMES IN ORGANIC CHEMISTRY
Why enzymes in organic synthesis?
| Alternative to chemical methods: * High region- and stereoselectivity * Milder reaction conditions * Environmentally more friendly
| Which enzyme(s)?
| Which reaction system?
| AqueousAqueous and water-miscible organic solventAqueous and water-immiscible organic solventPure organic solventOther solvents (supercritical fluids, ionic liquids)
| Which ‘chemistry’
| (dynamic) kinetic resolution vs. asymmetric sunthesis?Cofactor free or cofactor-dependent enzymes
Organic chemistry is the science concerned with all aspects of organic compounds. It is a sub discipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation (by synthesis or by other means) of carbon-based compounds, hydrocarbons, and their derivatives. These compounds may contain any number of other elements, including hydrogen, nitrogen, oxygen, the halogens as well as phosphorus, silicon, and sulfur. Organic synthesis is the methodology of their preparation. Organic compounds are molecules that contain carbon and hydrogen. All living things contain these organic molecules: carbohydrates, lipids, proteins, and nucleic acids. These molecules are often called macromolecules because they may be very large, containing thousands of carbon and hydrogen atoms and because they are typically composed of many smaller molecules bonded together. Enzymes are proteins that catalyze that is increase the rates of chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates sufficient for life. Since enzymes are selective for their substrates and speed up only a few reactions from among many possibilities, the set of enzymes made in a cell determines which metabolic pathways occur in that cell. The mechanism of enzyme in synthesis are:
1. Lock and key, developed by E. Fisher in 1894. Assumes rigid structure 2. Induced fit, Koshland Jr. in late 60s, enzyme can change its conformation 3. Desolvation theory, 1986 MJS Dewar – like gas phase rxns. Substrate replace H2O molecules from active site, then formal gas rxn takes place. In solution approach, this process is impeded by H2O. 4. Solvation Substitution theory, 1989 Warshel, Aqvist, and Creighton say no, energetically unfavored. Solvent is displaced by another environment provided by active site of enzyme The first application of enzymes in organic chemistry date back almost a century. As early as 1908, Rosenthaler used a hydroxynitrile lyase-containing extract for the preparation of (R)-mandelonitrile from benzaldehyde and hydrogen cyanide (HCN). Since then, an increasing number of enzymes have been identified, and their use in organic chemistry has steadily increased in parallel. In particular, since the mid-1970s the number of reports of enzymes utilization-which at present stands at more than 13000-as well as the number of industrialized enzyme-related processes has increased substantially. Several reasons can be identified for this development, including: * More organic chemists accept the use of biocatalyst
* Biocatalysis may save additional reaction steps compared to organic synthesis * Enzymes are often highly chemo-, region-, and stereospecific * Biocatalysis is a safer and ‘greener’ technology
* There is a substantially increased demand for optically pure compounds, especially for pharmaceutical applications * The production of biocatalysts has been made easier due to the development of recombinant expression systems * Many enzymes are available commercially
The most important application of enzymes in organic chemistry is in the synthesis of optically active compounds. This is due to the excellence...
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