Pyruvate aldolases in chiral carbon–carbon bond formation

Abstract

A procedure for the preparation of optically pure a-keto-c-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 b-hydroxy aldehydes and carboxylic acids, a-amino-c-hydroxy carboxylic acids and a,c-dihydroxy carboxylic acids. The protocol described here uses recombinant His 6 -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 c-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%.

Organocatalyzed Aldol Reaction between Pyridine‐2‐carbaldehydes and α‐Ketoacids: A Straightforward Route towards Indolizidines and Isotetronic Acids

“…Moderate yields resulted from the formation of unidentified by‐products, which were discarded upon crystallization. To the best of our knowledge, the reaction that provided pyridinium 4 e represents the first example of organocatalyzed aldol process that exploits pyruvic acid as a pronucleophile 11. The relative configuration of the C7 and C8 stereocenters in pyridinium salts 4 a – 4 h was assumed based on the configurations in compounds 4 a and 4 e that were obtained by X‐ray diffraction studies (Scheme and Scheme ).…”

“…To the best of our knowledge, the reaction that provided pyridinium 4 e represents the first example of organocatalyzed aldol process that exploits pyruvic acid as a pronucleophile. [11] The relative configuration of the C7 and C8 stereocenters in pyridinium salts 4 a-4 h was assumed based on the configurations in compounds 4 a and 4 e that were obtained by X-ray diffraction studies (Scheme 2 and Scheme 3). However, it is worthy of note that, in the solid state, a cis-C7-C9 relative configuration is found in compound 4 a, whilst it is trans in compound 4 e (see below).…”

Stable and efficient immobilization technique of aldolase under consecutive microwave irradiation at low temperature

“…In enzyme biocatalysis, aldolase has attracted the interest of organic chemists because of its ability to catalyze the formation of C-C bonds under mild conditions with stereospecific control and thus direct the synthesis of a single product (Bolt et al, 2008;Gillingham et al, 2010;Walters and Toone, 2007). Stereocontrolled C-C bond-forming reactions catalyzed by aldolase are also highly valuable tools in the synthesis of chiral molecules, especially in the pharmaceutical industry (Jennewein et al, 2006).…”

Enzyme‐Catalyzed Aldol Additions

“…GalA from E. coli was recently cloned, expressed, and characterized [57]. Application of GalA from E. coli and GlcA from Thermotoga maritima [58] yielded the two enantiomers, 48 and ent-48, precursors of the unnatural amino acid (2S,4S)-2-amino-4-hydroxy-4-(2-pyridyl) butyrate (Scheme 8.12) with high enantioselectivity [57,59].…”