Page - (000026) - in Biomedical Chemistry: Current Trends and Developments

rotation: when illuminated, as a solid or in solution, chiral molecules rotate the plane of polarization of light transmitting through it. One of the enantiomers rotates this plane clockwise by some amount dependant on concentration and path length of the light through the sample. The other enantiomer will rotate light by the same amount but anticlockwise. Racemic mixtures (racemates) are mixtures with same amount of both enantiomers of a compound and have a null optical rotation. Biological systems are highly stereospecific ‒ in general, only one stereoisomer is reactive towards an enzyme or a certain receptor. As a result, racemate resolution is of extreme importance for drug synthesis, particularly when one enantiomers has a negative effect. This problem is often solved by two different approaches: 1. Enzymatic resolution: the racemate is transformed in such a way that the resulting product may be then cleaved by an enzyme (e.g. lyase). Because of the stereospecificity of the enzyme, only one of the compounds is cleaved, enabling separation of cleaved and uncleaved product. 2. Diastereomeric resolution: the racemate is made to react with a specific, enantiomerically pure reagent (e.g. L-tartaric acid, to form an ester). The obtained products are diastereomers, which unlike enantiomers possess different properties and are therefore separable. After separation, the reverse reaction is performed to return the original enantiomers. 1.1.4 Common Mechanisms in Biological Chemistry Reactions that occur in living organisms follow the same rules of those occurring in the laboratory. The solvent, temperature and almost certainly the catalyst can be different, but the fundamental reaction mechanisms are the same. So conveniently, common organic reaction