Biomimetic studies

Biomimetic studies typically have one or more of the following objectives (i) to reproduce in a small synthetic molecule reactivity that was theretofore only observed in an enzyme (ii) to understand the mechanisms of an enzymatic reaction and the relationship between the stereoelectronic attributes of the catalytic site and its reactivity and (iii) to develop practical catalysts by exploiting and adopting solutions that evolved in Nature. Biomimetic studies of cytochrome c oxidase have been particularly impactfull in addressing aim (ii). On the other hand, this approach is... 

Boulatov R. 2004. Understanding the reaction that powers this world Biomimetic studies of respiratory O2 reduction by cytochrome oxidase. Pure Appl Chem 76 303. 

Collman JP, Sunderland CJ, Boulatov R. 2002c. Biomimetic studies of terminal oxidases Trisimidazole picket metalloporphyrins. Inorg Chem 41 2282. 

Different ligands applicable in biomimetic studies have been synthesized by ring-opening reaction of 1,4,7-triazatricyclo[5.2.1.04,10]decane 40 via alkylation (Scheme 33) <20010L2855>. 

The synthesis of bicyclic molecules containing guanidinium subunits, such as 156 (Scheme 22), are of considerable interest due to the wide range of biological activities presented by this family of natural products (see Section 11.11.9). In one of the first biomimetic studies toward ptylomycalin A, a series of polycyclic compounds have been prepared through an intermediate l-imino-hexahydropyrrolo[l,2-f]pyrimidin-3(4//)-one such as 155. Succinaldehyde... 

NT341 Arndt, R., J. E. Berg, and I. Wahlberg. Tobacco chemistry. Structure determi nation and biomimetic studies of five new tobacco cembranoids. Acta Chem Scand 1990 44(8) 814-825. 

A problem with the formation of the ternary ES—02 adduct is that it entails an attack of triplet 02 on the singlet substrate, which is a forbidden reaction. However, the presence of iron(III) may provide a mechanism for relaxing this barrier, as suggested by biomimetic studies showing that oxidative cleavage of catechols can be catalyzed by iron(III) centers [145,146], Building on this important early work, Que and coworkers synthesized a series of [Fe(L)(dbc)] complexes where L is a tetradentate tripodal ligand based on trimethylamine with... 

In contrast to achiral/racemic porphyrinoids, the chirogenic properties of chiral porphyrinoids have been scantily investigated despite their prime importance for chiral recognition, asymmetric catalysis, medical purposes, and various biomimetic studies. 

Of major importance to biomimetic studies have been the development of model systems that mimic the natural ones. Indeed, the basis for our understanding of coenzyme functions stems primarily from such studies with model systems. We can anticipate for the future, and the reader will see in the pages of this monograph, promise of the ability to understand and parallel in vitro the specificity and catalytic acceleration of enzymes themselves. 

A number of investigators (15, 16, 17), working with pyruvate decarboxylase, actually isolated the pyruvate adduct to thiamin pyrophosphate, and demonstrated that the enzyme will then decar-boxylate that adduct to yield C02 and acetaldehyde. In an elegant biomimetic study, Lienhard (18, 19) and his collaborators synthesized an analog of this adduct, and showed that it undergoes decarboxylation upon heating in water. Further, the rate is enhanced 105-fold by carry-... 

The goal of diiron model chemistry is to develop small molecule systems that accurately reproduce spectroscopic, structural, and more ambitiously, reactivity aspects of driron metaUoproteins. Despite being structurally similar, diiron enzymes carry out a variety of catalytic processes see Iron Proteins with Dinuclear Active Sites)Advancements in the synthesis and characterization of small molecule mimics for nonheme diiron enzymes have been tremendous in the last decade. Biomimetic studies have been carried out in efforts to reproduce the structural and functional aspects of these biocatalysts. Although this has been a challenging endeavor, much information regarding the structural and mechanistic aspects of catalytic intermediates has been obtained. 

As part of a biomimetic study for the enzyme class II aldolase" the equilibrium was reported for the cyclen complex, hydroxo-Zn(II)-l-(4-bromophenacyl)-l,4,7,10-tetraaza-cyclododecane and the intramolecular enolate 20, formed from Zn(II) and the enolate of l-(4-bromophenacyl)cyclen. This cyclization reaction was shown to be endothermic by 8.7 kJmol. However, with an entropy of 19 JmoU K it proceeds readily enough to show facile H/D exchange from the CH2 group of the exocyclic ligand. We wonder about the enthalpy and entropy changes associated with a different choice of other polyamines and/or central metals. 

Several biomimetic studies involving the nonenzymatic, intramolecular cyclization of synthetic peptides that contain dehydroamino acids and unprotected cysteine residues have been used to investigate the cyclization step of lantibiotic biosynthesis. Short peptides that contain a single Dha or Dhb residue and... 

Zhu Y, Gieselman M, Zhou H, Averin O, van der Donk WA. Biomimetic studies on the mechanism of stereoselective lanthionine formation. Org. Biomol. Chem. 2003 1 3304-3315. 

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