Synthesis and Characterization of CoII Macrocycles and its Use for Promoting Hydrolysis of Esters

The design and synthesis of hydrolytically active macrocycles mimic the substrate selectivity and rate enhancements for the hydrolysis of various organic substrates in high/low temperatures and extreme pH conditions, which is extremely challenging. In the present study, we synthesized two CoIIHMTAA-14 and CoIIHMTAA-16 macrocycles (HMTAA=hexamethyl-dibenzo-tetraaza-azulene) and used them to promote the hydrolysis of 4-nitrophenyl-2-benzamide carbonate and 4-nitrophenyl-4-benzamide carbonate esters. The effect of pH on hydrolysis of the carbonate esters was also studied at different pH 4.0, 6.5, and 8.5. The results of these studies showed that the reaction follows the first order with respect to ester concentration and is independent of the medium pH and water concentration. For the account of mechanism, hydrolysis of 4-nitrophenyl-2-benzamide carbonate and 4-nitrophenyl-4-benzamide carbonate proceeds either through oxygen or nitrogen intermolecular attack and normal H2O or OH- attacks, respectively. The plots of logkobs vs. pKa of the conjugate acid nucleophile showed leveling beyond pKa of about β = 0.3. The present macrocyclic complexes were found to provide enhanced hydrolysis of the esters.

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Characterization of 2β(R)-17-O-AcetylajmaIan: Acetylesterase — a Specific Enzyme Involved in the Biosynthesis of the Rauwolfia Alkaloid Ajmaline

Zeitschrift für Naturforschung C ◽

10.1515/znc-1987-0403 ◽

1987 ◽

Vol 42 (4) ◽

pp. 333-342 ◽

Cited By ~ 13

Author(s):

Leo Polz ◽

Helmut Schübel ◽

Joachim Stoekigt

Keyword(s):

Substrate Selectivity ◽

Specific Enzyme ◽

Naturally Occurring ◽

Optimum Ph ◽

Relative Molecular Weight ◽

Inhibition Studies ◽

Hydrolysis Of ◽

Activity Point ◽

Rauwolfia Alkaloid

A novel enzyme was isolated, partially purified (217-fold) and characterized from cell suspension cultures of Rauwolfia serpentina Benth. The enzyme catalyzes one of the late biochemical reactions in the biosynthesis of ajmaline by hydrolysis of 17-O-acetylated alkaloids of the ajmalan group forming the appropriate deacetylated compounds. This esterase exhibits an unusually high substrate selectivity and exclusively accepts acetylated ajmaline derivatives with the naturally occurring 2β(R)-configuration. The properties of the enzyme were determined showing an optimum pH at 7.5, an isoelectric point of pH 4.9 and a relative molecular weight of 33 ± 2 kDa. Inhibition studies of enzyme activity point to the necessity of SH-groups. The esterase seems not to be inhibited by ajmaline. the end product of the pathway. The highest enzyme activities were observed in leaves and cell suspension tissues of the tribe Rauwolfieae which are known to synthesize ajmaline and its congeners. The specific function of the esterase in the biosynthesis of the later alkaloids was established.

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Characterization of nanoprecipitates formed from the forced hydrolysis of bioleach liquors under different pH conditions

Journal of Industrial and Engineering Chemistry ◽

10.1016/j.jiec.2013.12.051 ◽

2014 ◽

Vol 20 (5) ◽

pp. 3578-3583 ◽

Cited By ~ 1

Author(s):

Sehliselo Ndlovu ◽

Geoffrey S. Simate ◽

Kudzai A. Mchibwa ◽

Alejandra Giaveno

Keyword(s):

Forced Hydrolysis ◽

Ph Conditions ◽

Hydrolysis Of

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The Effects of Amines on the Esterase Activities of Thrombin and Thrombokinase and on Several Clotting Tests

Thrombosis and Haemostasis ◽

10.1055/s-0038-1649165 ◽

1974 ◽

Vol 31 (02) ◽

pp. 309-318

Author(s):

Phyllis S Roberts ◽

Raphael M Ottenbrite ◽

Patricia B Fleming ◽

James Wigand

Keyword(s):

Choline Chloride ◽

Polymerization Process ◽

Ammonium Bromide ◽

Bovine Thrombin ◽

One Stage ◽

Human Proteins ◽

Rate Of Hydrolysis ◽

The One ◽

Hydrolysis Of Esters ◽

Hydrolysis Of

Summary1. Choline chloride, 0.1 M (in 0.25 M Tris. HCl buffer, pH 7.4 or 8.0, 37°), doubles the rate of hydrolysis of TAME by bovine thrombokinase but has no effect on the hydrolysis of this ester by either human or bovine thrombin. Only when 1.0 M or more choline chloride is present is the hydrolysis of BAME by thrombokinase or thrombin weakly inhibited. Evidence is presented that shows that these effects are due to the quaternary amine group.2. Tetramethyl ammonium bromide or chloride has about the same effects on the hydrolysis of esters by these enzymes as does choline chloride but tetra-ethyl, -n.propyl and -n.butyl ammonium bromides (0.1 M) are stronger accelerators of the thrombokinase-TAME reaction and they also accelerate, but to a lesser degree, the thrombin-TAME reaction. In addition, they inhibit the hydrolysis of BAME by both enzymes. Their effects on these reactions, however, do not follow any regular order. The tetraethyl compound is the strongest accelerator of the thrombokinase-TAME reaction but the tetra-ethyl and -butyl compounds are the strongest accelerators of the thrombin-TAME reaction. The ethyl and propyl compounds are the best (although weak) inhibitors of the thrombokinase-BAME and the propyl compound of the thrombin-BAME reactions.3. Tetra-methyl, -ethyl, -n.propyl and -n.butyl ammonium bromides (0.01 M) inhibit the clotting of fibrinogen by thrombin (bovine and human proteins) at pH 7.4, imidazole or pH 6.1, phosphate buffers and they also inhibit, but to a lesser degree, a modified one-stage prothrombin test. In all cases the inhibition increases regularly as the size of the alkyl group increases from methyl to butyl. Only the ethyl com pound (0.025 M but not 0.01 M), however, significantly inhibits the polymerization of bovine fibrin monomers. It was concluded that inhibition of the fibrinogen-thrombin and the one-stage tests by the quaternary amines is not due to any effect of the com pounds on the polymerization process but probably due to inhibition of thrombin’s action on fibrinogen by the quaternary amines.

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The effect of polymeric and model imidazolium halides on the rate of hydrolysis of 4-acetoxy-3-nitrobenzoic acid

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19850845 ◽

1985 ◽

Vol 50 (4) ◽

pp. 845-853 ◽

Cited By ~ 3

Author(s):

Miloslav Šorm ◽

Miloslav Procházka ◽

Jaroslav Kálal

Keyword(s):

Catalyst Concentration ◽

Low Molecular Weight ◽

Imidazolium Chloride ◽

First Order ◽

Nitrobenzoic Acid ◽

Rate Of Hydrolysis ◽

Acid Catalyzed ◽

Hydrolysis Of ◽

Ethanol In Water ◽

Direct Attack

The course of hydrolysis of an ester, 4-acetoxy-3-nitrobenzoic acid catalyzed with poly(1-methyl-3-allylimidazolium bromide) (IIa), poly[l-methyl-3-(2-propinyl)imidazolium chloride] (IIb) and poly[l-methyl-3-(2-methacryloyloxyethyl)imidazolium bromide] (IIc) in a 28.5% aqueous ethanol was investigated as a function of pH and compared with low-molecular weight models, viz., l-methyl-3-alkylimidazolium bromides (the alkyl group being methyl, propyl, and hexyl, resp). Polymers IIb, IIc possessed a higher activity at pH above 9, while the models were more active at a lower pH with a maximum at pH 7.67. The catalytic activity at the higher pH is attributed to an attack by the OH- group, while at the lower pH it is assigned to a direct attack of water on the substrate. The rate of hydrolysis of 4-acetoxy-3-nitrobenzoic acid is proportional to the catalyst concentration [IIc] and proceeds as a first-order reaction. The hydrolysis depends on the composition of the solvent and was highest at 28.5% (vol.) of ethanol in water. The hydrolysis of a neutral ester, 4-nitrophenyl acetate, was not accelerated by IIc.

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ChemInform Abstract: Chemical Characterization of a New 5,7-Diamino-3,5,7,9-tetradeoxynonulosonic Acid (I) Released by Mild Acid Hydrolysis of the Legionella pneumophila Serogroup 1 Lipopolysaccharide.

ChemInform ◽

10.1002/chin.199807224 ◽

2010 ◽

Vol 29 (7) ◽

pp. no-no

Author(s):

YU. A. KNIREL ◽

H. MOLL ◽

J. H. HELBIG ◽

U. ZAEHRINGER

Keyword(s):

Acid Hydrolysis ◽

Legionella Pneumophila ◽

Chemical Characterization ◽

Mild Acid Hydrolysis ◽

Hydrolysis Of ◽

Mild Acid

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295. Ion-exchange resins as catalysts in the hydrolysis of esters

Journal of the Chemical Society (Resumed) ◽

10.1039/jr9520001607 ◽

1952 ◽

pp. 1607 ◽

Cited By ~ 45

Author(s):

C. W. Davies ◽

G. Garrod Thomas

Keyword(s):

Ion Exchange ◽

Ion Exchange Resins ◽

Exchange Resins ◽

Hydrolysis Of Esters ◽

Hydrolysis Of

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MW irradiation and ionic liquids as green tools in hydrolyses and alcoholyses

Green Processing and Synthesis ◽

10.1515/gps-2021-0001 ◽

2020 ◽

Vol 10 (1) ◽

pp. 001-010 ◽

Cited By ~ 1

Author(s):

Nikoletta Harsági ◽

Betti Szőllősi ◽

Nóra Zsuzsa Kiss ◽

György Keglevich

Keyword(s):

Ionic Liquids ◽

Alkaline Hydrolysis ◽

Alkyl Group ◽

Phosphinic Acid ◽

Reaction Times ◽

Alternative Possibility ◽

First Order ◽

Pseudo First Order ◽

Mw Irradiation ◽

Hydrolysis Of

Abstract The optimized HCl-catalyzed hydrolysis of alkyl diphenylphosphinates is described. The reaction times and pseudo-first-order rate constants suggested the iPr > Me > Et ∼ Pr ∼ Bu order of reactivity in respect of the alkyl group of the phosphinates. The MW-assisted p-toluenesulfonic acid (PTSA)-catalyzed variation means a better alternative possibility due to the shorter reaction times, and the alkaline hydrolysis is another option. The transesterification of alkyl diphenylphosphinates took place only in the presence of suitable ionic liquids, such as butyl-methylimidazolium hexafluorophosphorate ([bmim][PF6]) and butyl-methylimidazolium tetrafluoroborate ([bmim][BF4]). The application of ethyl-methylimidazolium hydrosulfate ([emim][HSO4]) and butyl-methylimidazolium chloride ([bmim][Cl]) was not too efficient, as the formation of the ester was accompanied by the fission of the O–C bond resulting in the formation of Ph2P(O)OH. This surprising transformation may be utilized in the phosphinate → phosphinic acid conversion.

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Pretreatment of Switchgrass for Production of Glucose via Sulfonic Acid-Impregnated Activated Carbon

Processes ◽

10.3390/pr9030504 ◽

2021 ◽

Vol 9 (3) ◽

pp. 504

Author(s):

Yane Ansanay ◽

Praveen Kolar ◽

Ratna Sharma-Shivappa ◽

Jay Cheng ◽

Consuelo Arellano

Keyword(s):

Activated Carbon ◽

Sulfonic Acid ◽

Solid Acid ◽

Methanesulfonic Acid ◽

Biofuel Production ◽

Acid Catalysts ◽

Effects Of Temperature ◽

Carbon Catalysts ◽

Hydrolysis Of

In the present research, activated carbon-supported sulfonic acid catalysts were synthesized and tested as pretreatment agents for the conversion of switchgrass into glucose. The catalysts were synthesized by reacting sulfuric acid, methanesulfonic acid, and p-toluenesulfonic acid with activated carbon. The characterization of catalysts suggested an increase in surface acidities, while surface area and pore volumes decreased because of sulfonation. Batch experiments were performed in 125 mL serum bottles to investigate the effects of temperature (30, 60, and 90 °C), reaction time (90 and 120 min) on the yields of glucose. Enzymatic hydrolysis of pretreated switchgrass using Ctec2 yielded up to 57.13% glucose. Durability tests indicated that sulfonic solid-impregnated carbon catalysts were able to maintain activity even after three cycles. From the results obtained, the solid acid catalysts appear to serve as effective pretreatment agents and can potentially reduce the use of conventional liquid acids and bases in biomass-into-biofuel production.

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