Steric inhibitor

Systemic fungi- 743-745 cide acting as a steric inhibitor towards succinate deshy-drc gcnasc... 

The design of potent inactivators requires the determination of the functional groups necessary for optimal binding of the inhibitor to the enzyme. Next, the regions of steric tolerance are identified that will be useful for introduction of the reactive group. The reactivity as well as the size of the reactive... 

Inhibition of a regulatory enzyme by a feedback inhibitor does not conform to any normal inhibition pattern, and the feedback inhibitor F bears little structural similarity to A, the substrate for the regulatory enzyme. F apparently acts at a binding site distinct from the substrate-binding site. The term allosteric is apt, because F is sterically dissimilar and, moreover, acts at a site other than the site for S. Its effect is called allosteric Inhibition. 

In this chapter, an attempt has been made to present a total number of 20 QSAR models (12 QSAR models for topo I inhibitors and eight QSAR models for topo II inhibitors) on 11 different heterocyclic compound series (an-thrapyrazoles, benzimidazoles, benzonaphthofurandiones, camptothecins, desoxypodophyllotoxins, isoaurostatins, naphthyridinones, phenanthridines, quinolines, quinolones, and terpenes) as well as on some miscellaneous heterocyclic compounds for their inhibition against topo I and II. They have been found to be well-correlated with a number of physicochemical and structural parameters. The conclusion, from the analysis of these 20 QSAR, has been drawn that the inhibition of topo I is largely dependent on the hydrophobicity of the compounds/substituents. On the other hand, steric parameters (molar refractivity, molar volume, and Verloop s sterimol parameters) are important for topo II inhibition. 

Steric effects and FMO control have been combined in an elegant way to achieve regiospecific synthesis of pyrazole inhibitors of dihydroorotate dehydrogenase <2006SL901>. When the size of the propargylic acid ester 86 is increased from ethyl to diphenylmethyl, pyrazole 87 is formed from compound 85 regiospecifically (Scheme 3 Table 4) <2006H(68)1007>. 

As the reaction temperature increases, the equilibrium constant diminishes, since complex formation is accompanied by heat liberation. Sterically hindered phenols form loose complexes because of the impeding effect of voluminous alkyl substituents in the ortho-position. Hydrogen bonding reduces the activity of phenols, which was first observed in the studies of the effects of cyclohexanol and butanol on the inhibitory activity of a-naphthol in cyclohexane [9]. This phenomenon was investigated in detail with reference to the oxidation of methylethylketone [10]. The k7 values for some inhibitors of the oxidation of ethylbenzene and methylethylketone are given below (333 K) [10,46] ... 

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