Lipase catalysis enantioselective acylation

A prominent example of chemoenzymatic catalysis in bio-organic chemistry is the dynamic kinetic resolution (DKR) of secondary alcohols (Scheme 9) [94, 95] and amines [96-99], In this process, a lipase is employed as an enantioselective acylation catalyst, and a metal-based catalyst ensures continuous racemization of the unreactive enantiomer. 

These findings led to elucidation of the mechanistic aspects of Upase (Novozym 435) catalysis enantioselection is operated by the deacylation step as shown in Fig. 3 [53], where only dimer formation is shown for simphcity. It is well accepted that at first the monomer (substrate) is activated by enzyme with formatimi of an (/ )-acyl-enzyme intermediate (enzyme-activated monomer, EM) [ acylation of lipase step (a) in Fig. 3]. Onto the activated carlxMiyl carbon of EM, the OH group of the D-lactate nucleophUically attacks to form an ester bond, liberating Upase enzyme and giving rise to D,D-dimer [ deacylation of Upase step (b) in Fig. 3]. 

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