An Introduction to Asymmetric Synthesis

A molecule is chiral if it has a non-superimposable mirror image (Eigure 2.1). The most common cause of chirality in molecules is the presence of asymmetric carbon atom(s). The majority of pharmaceuticals and natural products are in single-enantiomer form. Asymmetric synthesis plays a key role in the preparation of these compounds of interest. Stereoselective synthesis of chiral compounds, as defined by lUPAC, is a chemical reaction in which one or more new elements of chirality are formed in a substrate molecule, produeing the stereoisomeric products in unequal amounts. Asymmetric synthesis is particularly important in the fields of pharmaceuticals and agrochemicals, because the different enantiomers or diastereomers of a molecule often have different biological activities. 

Chirality is becoming increasingly common in pharmaceuticals, as well as in the fine chemical industry. As reported, as many as 80% of the 

The approaches to preparing a single enantiomer or diastereomer of a chiral molecule include  

Apart from enantioselective synthesis, optically pure compounds can be obtained by chiral resolution. This involves the isolation of one enantiomer from a racemic mixture by a number of methods. This route remains cost-effective when the time and money required for making racemic mixtures are low, or both enantiomers have a separate use. 

As listed in Table 2.1, biocatalytic technology employing either isolated enzymes or whole-cell biocatalysts is gaining popularity due to its superior chemoselectivity, regioselectivity, or stereoselectivity, as well as mild reaction conditions and environmental biocompatibility. 

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