Search results for "HYDROLYSIS"
showing 10 items of 632 documents
Syntheses, X-ray structures, and physicochemical properties of phenoxo-bridged dinuclear nickel(II) complexes: kinetics of transesterification of 2-h…
2009
Four dinuclear nickel(II) complexes [Ni(II)(2)(L(1))(O(2)CMe)(2)(H(2)O)(2)][PF(6)].MeOH.3H(2)O (1), [Ni(II)(2)(L(1))(O(2)CMe)(2)(NCS)] (2), [Ni(II)(2)(L(2))(O(2)CMe)(2)(MeOH)(H(2)O)][ClO(4)] (3), and [Ni(II)(2)(L(2))(O(2)CMe)(2)(MeOH)(H(2)O)][BPh(4)].3MeOH.H(2)O (4) have been synthesized [HL(1): 2,6-bis[N-methyl-N-(2-pyridylethyl)amino]-4-methylphenol; HL(2): 2,6-bis[3-(pyridin-2-yl)pyrazol-1-ylmethyl]-4-methylphenol]. Complexes 1, 3, and 4 are new while complex 2 was reported previously by Fenton and co-workers (the structure of 2 was presented but no physicochemical properties of this complex were reported; in this work such studies have been completed). X-ray crystallographic analyses of…
C,N-chelated organotin(IV) trifluoroacetates. Instability of the mono- and diorganotin(IV) derivatives.
2011
Abstract The C,N-chelated tri-, di- and monoorganotin(IV) halides react with equimolar amounts of CF3COOAg to give corresponding C,N-chelated organotin(IV) trifluoroacetates. The set of prepared tri-, di- and monoorganotin(IV) trifluoroacetates bearing the LCN ligand (where LCN is 2-(N,N-dimethylaminomethyl)phenyl-) was structurally characterized by X-ray diffraction analyses, multinuclear NMR and IR spectroscopy. In the case of triorganotin(IV) trifluoroacetates and (LCN)2Sn(OC(O)CF3)2, no tendency to form hydrolytic products, or instability towards the moisture was observed. LCNRSn(OC(O)CF3)2 (where R is n-Bu or Ph) and LCNSn(OC(O)CF3)3 forms upon crystallization from THF in the air mainl…
Acylated oleanane-type saponins from Ganophyllum giganteum
2014
Abstract Five oleanane-type saponins , 3- O -β- D -glucuronopyranosylzanhic acid 28- O -β- D -xylopyranosyl-(1→3)-[α- L -rhamnopyranosyl-(1→2)]-(4- O -acetyl)-β- D -fucopyranosyl ester ( 1 ), 3- O -β- D -glucopyranosylzanhic acid 28- O -β- D -xylopyranosyl-(1→3)-[α- L -rhamnopyranosyl-(1→2)]-(4- O -acetyl)-β- D -fucopyranosyl ester ( 2 ), zanhic acid 28- O -β- D -xylopyranosyl-(1→3)-[α- L -rhamnopyranosyl-(1→2)]-(4- O -acetyl)-β- D -fucopyranosyl ester ( 3 ), zanhic acid 28- O -α- L -rhamnopyranosyl-(1→2)-4- O -[(3′-hydroxy-2′-methyl-butyroyloxy)-3-hydroxy-2-methyl-butyroyloxy]-β- D -fucopyranosyl ester ( 4 ), medicagenic acid 28- O -α- L -rhamnopyranosyl-(1→2)-4- O -[(3′-hydroxy-2′-methyl-…
Novel Acylated Triterpene Glycosides from Muraltia heisteria
2002
Four new acylated triterpene glycosides (1-4) have been isolated as two inseparable mixtures of the trans- and cis-3,4,5-trimethoxycinnamoyl derivatives (1,2 and 3,4) from the roots of Muraltia heisteria. The structures of these compounds were elucidated by various 1D and 2D NMR techniques, including (1)H and (13)C, COSY, NOESY, HSQC, TOCSY, and HMBC experiments and FABMS. Compounds 3 and 4 were shown to be cytotoxic in a human colon cancer cell line but did not show any ability to potentiate in vitro cisplatin cytotoxicity.
Acylated Preatroxigenin Glycosides from Atroxima congolana
2003
Six new acylated bisdesmosidic preatroxigenin saponins named atroximasaponins E1, E2 (1, 2), F1, F2 (3, 4), and G1, G2 (5, 6) were isolated as three inseparable mixtures of the trans- and cis-p-methoxycinnamoyl derivatives, from the roots of Atroxima congolana. Their structures were established through extensive NMR spectroscopic analysis as 3-O-beta-D-glucopyranosylpreatroxigenin-28-O-beta-D-xylopyranosyl-(1--4)-alpha-L-rhamnopyranosyl-(1--2)-[beta-D-glucopyranosyl-(1--3)]-[4-O-trans-p-methoxycinnamoyl]-beta-D-fucopyranoside (atroximasaponin E1, 1), and its cis-isomer, atroximasaponin E2 (2), 3-O-beta-D-glucopyranosylpreatroxigenin-28-O-beta-D-xylopyranosyl-(1--4)-alpha-L-rhamnopyranosyl-(…
Syntheses of Four Enantiomers of 2,3-Diendo- and 3-Endo-aminobicyclo[2.2.2]oct-5-ene-2-exo-carboxylic Acid and Their Saturated Analogues
2013
Abstract: Ethyl 2,3- diendo -3-aminobicyclo[2.2.2]oct- 5-ene-2-carboxylate ((±)- 1 ) was resolved with O , O '-dibenzoyltartaric acid via diastere omeric salt formation. The efficient synthesis of the enantiomers of 2,3- diendo -3-aminobicyclo[2.2.2]oct- 5-ene-2-carboxylic acid ((+)- 7 and (–)- 7 ), 3- endo -aminobicyclo[2.2.2]oct-5-ene-2- exo -carboxylic acid ((+)- 5 and (–)- 5 ), cis - and trans -3-aminobicyclo[2.2.2]octa ne-2-carboxylic acid ((+)- 6 , (–)- 6 , (+)- 8 and (–)- 8 ) was achieved via isomerization, hydrogenation and hydrolysis of the corresponding esters (–)- 1 and (+)- 1 . The stereochemistry and relative configurations of the synthesized compounds were determined by NMR sp…
Reaction Rate Modeling in Cryoconcentrated Solutions: Alkaline Phosphatase Catalyzed DNPP Hydrolysis
2000
The hydrolysis of disodium p-nitrophenyl phosphate catalyzed by alkaline phosphatase was chosen as a model to study the kinetics of changes in frozen food products. The initial reaction rate was determined in concentrated sucrose solutions down to -24 degrees C, and the enzymatic characteristics K(M) and V(max) were calculated. The experimental data were compared to the kinetics predicted by assuming that the reaction was viscosity dependent. Indeed, an analysis of the enzymatic reaction demonstrated that both the diffusion of the substrate and the flexibility of the enzyme segments were controlled by the high viscosity of the media. When the temperature was too low for the viscosity to be …
Regioselective substitution of 6,7-dichloroquinoline-5,8-dione: synthesis and X-ray crystal structure of 4a,10,11-triazabenzo[3,2-a]fluorene-5,6-dion…
2003
6,7-Dichloroquinoline-5,8-dione (1) was reacted with a number of 2-aminopyridine derivatives. Of the several possible products of this reaction, 4a,10,11-triazabenzo[3,2-a]fluorene-5,6-dione (6), produced by condensation and rearrangement, was obtained as the major product, and its structure was subsequently unambigously determined by X-ray crystallographic study. Ortho-quinones were produced via nucleophilic substitution at position C7, which was unexpected, considering that para-quinones were produced via C6 substitution in the reaction between compound 1 and ethyl acetoacetate in our previous work. Such unexpected nucleophilic substitution at C7 provides an effective, yet simple route, t…
Crystal structure of [Cu(N-quinolin-8-yl-p-toluenesulfonamidate)2]: study of its interaction with DNA and hydrogen peroxide
2001
A new copper complex with N-quinolin-8-yl-p-toulenesulfonamide has been prepared and characterised. The compound crystallises in the triclinic system, space group P1, with a=13.457(3), b=15.067(5), c=18.589(3) A; α=112.05(2), β=93.92(2), γ=108.30(2)° and Z=4. The geometry of the Cu(II) ion is distorted square planar. The N-quinolin-8-yl-p-toulenesulfonamidate anion behaves as a bidentate ligand through the N s u l f o n a m i d a t e and N q u i n o l i n e atoms. The complex does not cleave DNA in the presence of hydrogen peroxide.
Critical parameters for adduct formation of the carcinogen (+)-anti-benzo[a]pyrene-7,8-dihydrodiol 9,10-epoxide with oligonucleotides.
1997
Various parameters relevant for the formation of dG adducts produced in the reaction of individual benzo[a]pyrene diol epoxide (BPDE) stereoisomers with oligonucleotides have been studied. Reaction time, temperature, pH, molar ratio of diol epoxide and oligonucleotide, base sequence, and buffer system were shown to affect the amount of (+)-anti-BPDE dG adducts formed. Optimum experimental conditions for dG adduct formation were different depending on the base sequence context of the oligonucleotide employed [5'-d(CCTATAGATATCC) or 5'-d(CCTATTGCTATCC)]. In general, low temperature to allow a longer reaction time, slightly alkaline Tris-HCl (pH 7.5-8.0) or alkaline phosphate buffer (pH 11), l…