Hydrolysis of phosphate esters with polymer-supported catalysts containing cyclodextrin pendant group

Abstract

Polymer-supported catalysts of several kinds, including /3-cyclodextfin (P-CD), fl-cyclodextrin-diethylenetriamine (P-CD-DETA), and fl-cyclodextrin-N-methylhydroxamate (P-CD-NMHA)-containing polymers, as well as their corresponding metal complexes, were synthesized and examined as catalysts for the hydrolysis of phosphate esters. The kinetic measurements were performed in a phosphate buffer (0.05 M, pH 8.2) at a temperature of 25.0 4-0.1 o C. Each kinetic run was initiated on introducing ester stock solution (0.13 ml) containing diphenyl p-nitrophenyl phosphate (DPPNPP) in dioxane (0.010 M). The rate of hydrolysis of DPPNPP was evaluated by measuring the absorbance of liberated p-nitrophenol at 402 run. The dissociation constants between DPPNPP and the polymers P-CD, P-CD-DETA and P-CD-NMHA obtained from Eadie-type plots were 16.8, 16.4 and 8.0 (x 10 -3 M) and the acceleration factors were 1.5, 2.8 and 8.6 respectively. Hence P-CD-NMHA is the most promising catalyst. The activation parameters, preexponential factor (A) and activation energy using P-CD-NMHA as catalyst, are A = 1.2 x 10 9 min -1 and E~ = 43 kJ/mol respectively; the latter was about 12 kJ/mol lower than the activation energy of spontaneous hydrolysis. The results indicate that the catalytic power of P-CD-NMHA may reflect the combined behavior of molecular recognition and nucleophilicity.

Biomimetic Reactions Catalyzed by Cyclodextrins and Their Derivatives

“…[132][133][134] Polymers containing cyclodextrins have also been examined for phosphate cleavages. 135 Simple cyclodextrins can act as catalysts and not just reactants. The earliest example was the chlorination of anisole catalyzed by R-CD (Figure 6).…”

“…Cleavage of phosphate esters by nucleophilic attack of a cyclodextrin oxyanion, to form a phosphorylated cyclodextrin, has also been studied . Simple β-CD accelerates the cleavage of bis( p -nitrophenyl) phosphate by almost 2 orders of magnitude, and some fluorophosphate nerve gases acylate cyclodextrins rapidly. − Polymers containing cyclodextrins have also been examined for phosphate cleavages …”

Synergistic effect of hydrogen bonding mediated selective synthesis of benzaldehyde in water

“…However, -CD is not a good model for enzyme catalysis because -CD has limited catalytic activity due to the weak intermolecular interactions between -CD and the substrate. If the catalytic site could have the synergistic effects of more functional groups, recognition should be more precise, and more like what is seen in enzyme recognition [17][18][19]. But to the best of our knowledge, -CD derivatives based on the synergistic effects of multiple hydrogen bonds have not been applied to organic reactions, despite some reports on the acceleration of reaction rates and obvious enhancements in selectivity [20][21][22].…”

Molecular Recognition of the Macrocyclic Polyamine for the Hydrolysis of Nucleotides in the Electrophoretic Condition

“…E-mail: cliu@ccms.ntu.edu.tw al. [12], and that of phosphate esters with polymersupported catalysts containing cyclodextrin pendant group has also been investigated in our lab [13]. Recently a 28-membered macrocyclic polyamine, 4,8,12,18,22,26hexaaza-1,15-dioxacyclooctaeicosane ([28]ane-N 6 O 2 ) bonded phase was prepared and evaluated for its use in the electrophoretic separation of organic and inorganic anions and metal ion speciation [14][15][16][17][18].…”