The catalytic carboxyester hydrolysis by a new zinc(II) complex with an alcohol-pendant cyclen (1-(2-hydroxyethyl)-1,4,7,10-tetraazacyclododecane): A novel model for indirect activation of the serine nucleophile by zinc(II) in zinc enzymes

Koike, Takao; Kajitani, Satoko; Nakamura, Ikushi; Kimura, Eiichi; Shiro, Motoo

doi:10.1021/ja00109a004

Cited by 186 publications

(143 citation statements)

References 1 publication

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“…1 A representative figure showing the increase in the absorbance of the released 4-nitrophenolate at 360 nm for the reaction of 2 (1.5 mM) with 4-nitrophenyl trifluoroacetate (0.15 mM) in CH 3 CN at 300 K of phosphate as well as carboxylate ester. Like other researchers [26][27][28] we too observe that with Tp ligand system also, the hydrolysis of both phosphate as well as carboxylate ester is slower with catalyst 4 in comparison to 2. The k 2 values obtained by 4 are smaller than that of 2.…”

Section: Hydrolysis Of Esterssupporting

confidence: 87%

“…The kinetic experiments indicated that the rate of generation of 4-nitrophenolate ion was varied from ester to ester and TpCoOH is the kinetically active species. The hydrolysis of ester occurs via a binuclear mechanism involving the nucleophilic attack of the metal-bound hydroxide to the carbonyl group of the ester as reported by other workers also [38][39][40][41][42][43][44]. The carbonic anhydrase also promotes the hydrolysis of 4-nitrophenylacetate [45] and follows second order kinetics, involving the direct nucleophilic attack at the carbonyl group by a Zn-OH species or hydroxo of other substituted metal ions.…”

Section: Discussionmentioning

confidence: 63%

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A mononuclear cobalt(II) hydroxo complex: synthesis, molecular structure, and reactivity studies

Babbar

Tyagi

Weyhermüller³

2008

Transition Met Chem

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A novel Co(II) hydroxo complex Co{HB(3- Prpz) 3 = hydrotris(3-tert-butyl-5-isopropylpyrazol-l-yl)borate} has been prepared and its molecular structure has been determined by X-ray crystallography. This complex is mononuclear with distorted tetrahedral geometry. The reaction of CO 2 with Co{HB(3- Prpz) 3 }] 2 (CO 3 ) wherein the carbonate group is bound to both metal centers in an asymmetrical manner. In order to explore the role of labile metal complexes in promoting ester hydrolysis, complexes [Co{HB(3,

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Section: Hydrolysis Of Esterssupporting

confidence: 87%

Section: Discussionmentioning

confidence: 63%

A mononuclear cobalt(II) hydroxo complex: synthesis, molecular structure, and reactivity studies

Babbar

Tyagi

Weyhermüller³

2008

Transition Met Chem

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“…In our case the reaction rates cannot be compared with those for the hydroxide ion in water, since our measurements were made in chloroform. Like the other researchers [37,39,65] we do observe that p-nitrophenylacetate hydrolysis is 2 ± 3 orders of magnitude slower than tris(p-nitrophenyl)phosphate hydrolysis by the same [L n ZnÀOH] species. However, in the absence of systematic variations of the substrates or the reaction conditions we have no further arguments for a mechanistic discrimination between organophosphate and carboxylic ester hydrolysis.…”

supporting

confidence: 85%

“…Accelerations by one or two orders of magnitude were observed when the ligands used bore pendant alkoxide groups, which assist the hydrolytic process. [65,66] Considering that the cleavage of 13 by 3 was performed in chloroform, that is, a solvent of much lower polarity, one can conclude that the hydrolytic activity of 3 actually corresponds to those of the reference compounds, as also evidenced above for the organophosphate cleavages.…”

mentioning

confidence: 60%

Evidence for a Trajectory of Hydrolytic Reactions brought about by [L3Zn−OH] Species

et al. 1999

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A kinetic study has been performed on the hydrolytic cleavage of various triorganophosphates PO-(OR) 2 (OR') by three pyrazolylborate ± zinc hydroxide complexes [Tp'Zn À OH] to form [Tp'Zn À OPO(OR) 2 ] and HOR'. The nature of the reactions (first order both in the zinc complex and the phosphate) and the strongly negative activation entropies (À 54 to À 126 J mol) indicate an intimate association of the ZnÀOH and PO functions in the rate-determining step. Some ester cleavages by [Tp'Zn À OH] show the same kinetic pattern and similar activation parameters. The observations are in accord with a four-center arrangement (ZnOPO or ZnOCO) in the activated complex, that is, the hybrid mechanism discussed for zinc enzyme as well as zinc complex catalyzed hydrolyses. A trajectory for reactions passing through this intermediate has been constructed with the Bürgi ± Dunitz structure correlation method, based on the geometries of 30 [Tp'Zn(X)(Y)] species with truly five-coordinate zinc centers. Its first step is the approach of the substrates oxygen atom to the tetrahedral L 3 ZnÀOH species along the axis of a trigonal bipyramid. In the resulting four-center intermediate with five-coordinate zinc a Berry pseudorotation describes the synchronous formation of the Zn À O-(substrate) and breaking of the ZnÀO-(OH) bonds. The concluding step in the coordination sphere of zinc is the expulsion of the former OH oxygen, now part of the substrate, again along the axis of a trigonal bipyramid. This mechanism, which is applicable to phosphate as well as to ester, amide, and carbon dioxide hydrolysis, is in accord with theoretical models of carbonic anhydrase action.

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“…In comparison to the parent cyclen system 1, which shows two nitrogen atoms with high basicity (pKa 11.0 Ϯ0.1 and 9.9 Ϯ0.1) and two nitrogen atoms with low basicity (pKa Ͻ 2), [30] compound 6b has one amino group with pKa of 11.3 Ϯ0.1, one with reduced basicity (pKa 6.3 Ϯ0.1), and one with low basicity (pKa Ͻ 2). Titration of biscyclen 9b shows that protonation of both monosubstituted azamacrocycles is independent: The pH profile is nearly identical to 6b, if equivalents of base (with respect to the number of cyclen moieties) are used (pKa 11.3 Ϯ0.1 and pKa of 6.3 Ϯ0.1).…”

Section: Determination Of Pka Values By Potentiometric Titrationmentioning

confidence: 96%

Urea Derivatives of 1,4,7,10-Tetraazacyclododecane − Synthesis and Binding Properties

et al. 2001

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Keywords: Azacrown ether / DNA binding / Macrocycles / Supramolecular chemistry / UreaThe reaction between 1,4,7,10-tetraazacyclododecane (cyclen) and partially protected derivatives and isocyanates gives macrocyclic ureas in good yields. Bridged biscyclens with aliphatic or aromatic spacers were obtained from the reaction between diisocyanates and partially protected cyclen. The substituted cyclen derivatives with one or two urea moieties coordinate zinc(II) and copper(II) ions to form stable mononuclear and dinuclear complexes. Potentiometric titration revealed that the urea substitution significantly changes the basicity of the remaining secondary amino groups of the macrocycle. In comparison with that of cyclen

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The catalytic carboxyester hydrolysis by a new zinc(II) complex with an alcohol-pendant cyclen (1-(2-hydroxyethyl)-1,4,7,10-tetraazacyclododecane): A novel model for indirect activation of the serine nucleophile by zinc(II) in zinc enzymes

Cited by 186 publications

References 1 publication

A mononuclear cobalt(II) hydroxo complex: synthesis, molecular structure, and reactivity studies

A mononuclear cobalt(II) hydroxo complex: synthesis, molecular structure, and reactivity studies

Evidence for a Trajectory of Hydrolytic Reactions brought about by [L3Zn−OH] Species

Urea Derivatives of 1,4,7,10-Tetraazacyclododecane − Synthesis and Binding Properties

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