Pyruvate aldolases in chiral carbon-carbon bond formation.

Nature protocols (2007-07-21)
Matthew J Walters, Eric J Toone

A procedure for the preparation of optically pure alpha-keto-gamma-hydroxy carboxylic acids through stereospecific aldol addition catalyzed by pyruvate aldolases from the Entner-Doudoroff and the DeLey-Doudoroff glycolytic pathways is described. This highly versatile fragment serves as a precursor for a variety of commonly encountered functionalities, including beta-hydroxy aldehydes and carboxylic acids, alpha-amino-gamma-hydroxy carboxylic acids and alpha,gamma-dihydroxy carboxylic acids. The protocol described here uses recombinant His6-tagged KDPG aldolase for the synthesis of (S)-4-hydroxy-2-keto-4-(2'-pyridyl)butyrate. A protocol for evaluating enantiomeric excess through formation of the gamma-lactone of the dithioacetal followed by chiral-phase gas-liquid chromatography is also described. Enzyme expression and enzymatic synthesis can be accomplished in approximately 1 week. The enzymatic aldol addition proceeds in nearly quantitative yields with enantiomeric excesses greater than 99.7%.

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Ethyl alcohol, Pure, 200 proof, anhydrous, ≥99.5%
Dichloromethane, HPLC Plus, for HPLC, GC, and residue analysis, ≥99.9%, contains 50-150 ppm amylene as stabilizer
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