Use of Aldolases for Asymmetric Synthesis

Josep L6pez-Santi n , (jregorio Alvaro , and Pere Clapds  

Aldolases are a group of C—C bond forming enzymes with widespread applications. The stereoselective aldol addition reaction catalyzed by aldolases represents an attractive alternative to conventional chiral organic chemistry methods for chemical and pharmaceutical industries. Aldolases are classified according to both their proposed catalytic mechanism and the structure of the donor substrate, their sources and microbial production processes being presented in this chapter. To design appropriate bioreactors for aldol synthesis, the characteristics of aldolase biocatalysts obtained after purification procedures in free and immobilized form are discussed. 

Aldolases are a specific group of lyases (aldehyde-lyases EC 4.1.2) catalyzing the reversible stereoselective addition of a donor compound (nucleophile) to an acceptor compound (electrophile). 

It involves the attack by the deprotonated a-carbon atom of an aldehyde or ketone on the carbonyl atom of another aldehyde or ketone, resulting in a (3-hydroxyaldehyde or a (3-hydroxyketone. While the donor compound for aldolases is usually invariable, the acceptor may vary, allowing the use of these biocatalysts in asymmetric synthesis (Takayama et al. 1997 Samland and Sprenger 2006). 

Aldolases are usually classified according to their catalytic mechanism as  

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