Enzymatic reactions stereoelectronic effect

Another stereoelectronic effect induced by electronegative substituents is the "Anh-Eisenstein effect [44] (Scheme 4.17) which can be of particular importance to the stereochemical outcome of enzymatic reactions involving fluorinated substrates [45]. In a-fluorocarbonyl compounds nucleophilic attack of the carbonyl group occurs preferentially anti to the fluorine substituent [46]. The resulting, unusually high stereospecificity, e.g. in some enzymatic reactions of fluorinated substrates [45], cannot be explained by the slightly different steric demands of hydrogen and fluorine alone. 

Redirecting reactions via conformational control In the final example of this chapter, we will show how understanding of enzyme stereoelectronics allows one to redirect reactivity of known substrate into a new direction. When the stractural constraints of enzyme active sites are removed, a new set of stereoelectronic constraints can be imposed on the same substrate to enforce a different reactivity. For example, the effect of stereoelectronic factors on the relative order of steps in the deprotonation/decarboxylation sequence were recently analyzed for an enzyme-catalyzed vs. Cu-catalyzed reactions of the similar substrates (Figure 11.66). The first process is involved in the biosynthesis of polyketides and fatty acids where enzymatic activation of... 

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