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|標題:||Hammett-Taft cross-interaction correlations for the inhibition mechanism of cholesterol esterase by substituted phenyl N-substituted carbamates||作者:||Lin, G.||關鍵字:||Hammett-Taft cross-interactions;cholesterol esterase inhibition;carbamate inhibitors;interaction constants;lipase;site;rat;activation;absorption||Project:||Journal of Physical Organic Chemistry||期刊/報告no：:||Journal of Physical Organic Chemistry, Volume 13, Issue 6, Page(s) 313-321.||摘要:||
With the modified Hammett-Taft cross-interaction variations, multiple linear regressions of the chemical shifts of NH protons, pK(a), logk([OH]), -logK(i), logk(c) and logk(i) values for both substituted phenyl N-n-butyl carbamates (1) and 4-nitrophenyl-N-substituted carbamates 2 give linear correlations, and the cross-interaction constants are -0.5, 0.3, -2.4, 2, 1 and 2, respectively. The cross-interaction constant for the correlation of the chemical shifts of NH protons indicates that the pseudo-traits conformers are major conformers of carbamates 1 and 2 in CDCl3. Thus, the distances between the substituents at nitrogen and phenyl of carbamates 1 and 2 are relatively longer. In the transition states of protonations of carbamates 1 and 2 in aqueous solution (pK(a)), those distances are also longer. However, those distances of transition states for the E1cB mechanism of the basic hydrolysis of carbamates 1 and 2 and for the cholesterol esterase inhibition mechanism by carbamates 1 and 2 are relatively shorter based on large absolute values of cross-interaction constants. Moreover, the cholesterol esterase inhibition mechanism by carbamates 1 and 2 is common in the formation of the tetrahedral intermediate and then the carbamyl enzyme. Based on the stereoelectronic effects, the x-ray structures of cholesterol esterase and large values of the cross-interaction constants, the inhibition mechanism of cholesterol esterase by carbamates 1 and 2 is proposed. Copyright (C) 2000 John Wiley & Sons, Ltd.
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