Biomimicking of Enzyme Catalysis

D Souza and Bender proposed the synthesis of a hydrolyzing cavity that mimicks chymotrypsin by attachment of selected substituents to a dextrine cavity (Fig. 7.9). 

The two examples shown in Figs. 7.9 and 7.10 illustrate attempts at synthesizing a biomimetic flexible environment with well-controlled electrostatics strategically placed in a small cavity to provide concerted activation of probe molecules. 

The principles of supramolecular catalysis relate to enzyme catalysis, because weak chemical bonds involving well defined hydrogen bonds are essential. Lehnl formulated two main steps required for supramolecular reactivity and catalysis  

The D Souza and Bender system shows many of these features. Systems that induce bond formation require the presence of several binding and reactive groups. The catalytic molecule should act as a co-receptor bringing together reactant, substrate and intermediate complex. As an example, Hisselni and Lehnl l demonstrated pyrophosphate formation from the intermediate phosphoramidate formed by phosphorylation of the macrocycle by ATP. In a second reaction step, the phosphoramidate reacts with a phosphate group to form pyrophosphate (see Fig. 7.10). 

Enzyme-mimicking systems that contain metal cations have also been designed. A very elegant supramolecular assembly was designed by Sanders et al.I l (see Fig. 7.11). They constructed trimeric porphyrin structures where Zn porphyrin moieties function as templates for the organization of substrates into a conformationaUy optimal configuration that undergoes an efficient acyl-transfer reaction or that lead to Diels Alder products. 

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