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2.1.2.4 Aldol Addition of Glycine to Aldehydes

DOI: 10.1055/sos-SD-215-00021

Clapés, P.Science of Synthesis: Biocatalysis in Organic Synthesis, (2015275.

The aldol addition of glycine to aldehydes is catalyzed by pyridoxal 5′-phosphate (PLP) dependent aldolases such as threonine aldolases (ThrA; EC 4.1.2.5) and serine hydroxymethyltransferase (SHMT; EC 2.1.2.1).[‌176‌‌179‌] Because two new stereogenic centers are formed, four possible stereoisomers can be formally obtained, depending on the specificity of the aldolase (Scheme 29).[‌178‌,‌180‌‌182‌] However, in contrast to the case of DHAP dependent aldolases, a set of four stereocomplementary enzymes has not yet been found in nature. Each enzyme exquisitely controls the specificity at the nucleophile configuration, i.e. 2S or 2R for the l- or d-threonine-type aldolases, respectively (Scheme 30). With respect to the β-carbon, l-specific threonine aldolases can further be divided into three sub-types: l-threonine aldolase (l-ThrA), which preferentially cleaves l-threonine (l-Thr); l-allo-threonine aldolase (l-allo-ThrA), which cleaves l-allo-threonine (l-allo-Thr); and l-low specificity threonine aldolase, which accepts both l-Thr and l-allo-Thr as substrates. Regarding the d-series only d-low specificity threonine aldolase (d-low-ThrA) has so far been found in nature.[‌178‌,‌183‌]

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References


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