Enzymatic Synthesis of a-Hydroxyketones Acyloins

The bifunctional nature and the presence of a stereocenter make a-hydroxyketones (acyloins) amenable to further synthetic transformations. There are two classical chemical syntheses for these a-hydroxyketones the acyloin condensation and the benzoin condensation. In the acyloin condensation a new carbon-carbon bond is formed by a reduction, for instance with sodium. In the benzoin condensation the new carbon-carbon bond is formed with the help of an umpolung, induced by the formation of a cyanohydrin. A number of enzymes catalyze this type of reaction, and as might be expected, the reaction conditions are considerably milder [2-4, 26, 27]. In addition the enzymes such as benzaldehyde lyase (BAL) catalyze the formation of a new carbon-carbon bond enantioselectively. Transketolases (TK) 

The enantioselective synthesis of a-hydroxyketones via a carbon-carbon bond forming reaction has received a significant impulse during recent years. Four different enzymes are commonly used for this reaction BAL, BFD, pyruvate decarboxylase (PDC) and TK. Many different compounds can be prepared with 

D-Ribose 5-phosphate D-Xylulose 5-phosphate D-Sedoheptulose 7-phosphate D-Glyceraldehyde 3-phosphate 

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