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Hydrolytic Cleavage (hydrolytic + cleavage)
Selected AbstractsIdentification of heat-induced degradation products from purified betanin, phyllocactin and hylocerenin by high-performance liquid chromatography/electrospray ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2005Kirsten M. Herbach Betanin, phyllocactin (malonylbetanin) and hylocerenin (3-hydroxy-3-methylglutarylbetanin) were isolated from purple pitaya (Hylocereus polyrhizus [Weber] Britton & Rose) juice, and their degradation products generated by heating at 85°C were subsequently monitored by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry. Thermal degradation of phyllocactin and hylocerenin in purified solution excluding the alleged protective effects by the juice matrix is reported for the first time. Betanin was predominantly degraded by hydrolytic cleavage, while decarboxylation and dehydrogenation were of minor relevance. In contrast, hylocerenin showed a strong tendency to decarboxylation and dehydrogenation, hydrolytic cleavage of the aldimine bond occurring secondarily. Phyllocactin degradation was most complex because of additional decarboxylation of the malonic acid moiety as well as generation and subsequent degradation of betanin due to phyllocactin demalonylation. Upon prolonged heating, all betacyanins under observation formed degradation products characterized by an additional double bond at C2C3. Hydrolytic cleavage of the aldimine bond of phyllocactin and hylocerenin yielded previously unknown acylated cyclo -dopa derivatives traceable by positive ionization, while application of ESI(,) facilitated the detection of a glycosylated aminopropanal derivative and dopamine, which have never been described before as betanin degradation products. Copyright © 2005 John Wiley & Sons, Ltd. [source] "Inhibition" of the Enzyme Model TpPh,MeZn,OH by Diketo CompoundsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2006Teame Tekeste Abstract In order to gain a structural understanding of zinc enzyme inhibition, the model complex TpPh,MeZn,OH was treated with various diketo compounds. ,-Keto carboxylic acids were attached to the zinc ion as anionic O,O-chelate ligands, of which benzoylformate was oxidatively decarboxylated in air to form the benzoate complex. Two functionalized ,-diketones did not use their functionality in forming the ,-diketonate complexes. Of the ,-diketones, 2,3-pentanedione formed the ,-keto enolate complex, while 1-phenyl-1,2-propanedione underwent oxidative C,C coupling resulting in a red dinuclear bis(,-keto enolato) complex. Of the diaryl-,-diketones, benzil did not react, but pyridil underwent hydrolytic cleavage to pyridine-2-carbaldehyde and picolinate, of which the latter was bound to the zinc ion as an N,O-chelate ligand.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Reaction of 1,2-Diaza-1,3-butadienes with Aminophosphorus Nucleophiles: A Practical Access to New Phosphorylated PyrazolonesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 35 2008Orazio A. Attanasi Abstract The reaction of 1,2-diaza-1,3-butadienes with dibenzyl diisopropylphosphoramidite, methyl tetraisopropylphosphorodiamidite or tris(dimethylamino)phosphane under solvent-free conditions gave stable ,-phosphoranylidene-hydrazones that, in turn, were transformed into the corresponding 5-oxo-4-phosphoranylidene-4,5-dihydro-1H -pyrazoles. X-ray diffraction analysis of one of these derivatives is reported. ,-Phosphoranylidene-hydrazones, derived from the reaction between 1,2-diaza-1,3-butadienes with dibenzyl diisopropylphosphoramidite, were converted by hydrolytic cleavage into (E)-hydrazono-phosphonates, which are useful for the preparation of the corresponding (3-oxo-2,3-dihydro-1H -pyrazol-4-yl)phosphonamidates.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] ,-Aminoadamantanecarboxylic Acids Through Direct C,H Bond AmidationsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 9 2007Lukas Wanka Abstract Utilizing bromine-free, direct C,H bond amidations we have synthesized a large variety of adamantane amides. Depending on the precursors used these amides directly yield pharmaceutically active aminoadamantanes or ,-aminoadamantanecarboxylic acids after hydrolytic cleavage. Theserigid analogues of ,-aminobutyric acid (GABA) were protected at the C- and N-termini and we synthesized a number of peptides incorporating ,-aminoadamantanecarboxylicacids in solution as well as via solid phase peptide synthesis. These peptides are promising scaffolds for applications in medicinal chemistry as well as in organocatalysis.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Enders' SAMP-Hydrazone as Traceless Auxiliary in the Asymmetric 1,4-Addition of Cuprates to EnonesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2010Karsten Sammet Abstract Conjugate additions of Gilman cyanocuprates to (S)- N -amino-2-(methoxymethyl)pyrrolidine (SAMP)-hydrazones 4, 5 derived from cyclic and acyclic ,,,-unsaturated ketones were investigated. A protocol utilizing copper(II) sulfate/ammonium chloride was evolved, which allowed cleavage of SAMP (S)- 1 under the hydrolysis and work-up conditions, followed by recovery of the auxiliary with ethylenediaminetetraacetic acid (EDTA). The enantioselectivity of cuprate additions was dominated for cyclic SAMP-hydrazones 4 by the cuprate alkyl substituent and the ring size, in the case of acyclic arylidene SAMP-hydrazones 5, however, by the nature of the aryl substituent. Electron-donating substituents gave poor enantiomeric excesses, whereas electron-withdrawing groups provided excellent ee values of 98,99%. The configuration of the new stereocenter was determined to be (R). Moreover, a reaction sequence was developed which integrates a tandem 1,4-addition/methylation and traceless hydrolytic cleavage of the auxiliary (S)- 1 in a one-pot reaction, resulting in enantiomerically pure methyl ketones 11,13, each of them with>99% ee. [source] Synthesis and characterization of alkylated N -vinylformamide monomers and their polymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2004Lianjun Shi Abstract N -alkyl- N -vinylformamide monomers (alkyl: n -butyl, hexyl, decyl, and dodecyl) are synthesized in two steps: first, preparation of N -vinylformamide potassium salt by the reaction of N -vinylformamide (NVF) with potassium t -butoxide, then reaction with alkyl bromide. All four monomers are liquid and are characterized by IR, 1H NMR, 13C NMR, and mass spectra. They exist as rotomers in solution and a 2D NOE experiment on the N -hexyl containing polymer shows the E isomer to be favored. The polymerizability of the four monomers is from good to fair, depending upon the length of alkyl chain on the N -atom--the longer the chain length, the lower lower the polymerizability of monomer. The hydrolysis of poly(N -hexyl- N -vinylformamide) and poly(N -dodecyl- N -vinylformamide) under acidic and basic conditions was examined. Studies show that hydrolytic cleavage of formyl groups of poly (N -alkylated- N -vinylformamide) depends on the hydrophobicity of the alkyl substituent on the N -atom under acidic conditions; both polymers were hydrolyzed to only a minor extent under alkaline conditions. The N -alkylated monomers can copolymerize with NVF and demonstrate amphiphilic properties. The copolymers demonstrate a critical aggregation concentration above which they can solubilize a water insoluble dye; the N -hexyl containing copolymer stabilizes a castor oil-in-water emulsion. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4994,5004, 2004 [source] Identification of heat-induced degradation products from purified betanin, phyllocactin and hylocerenin by high-performance liquid chromatography/electrospray ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2005Kirsten M. Herbach Betanin, phyllocactin (malonylbetanin) and hylocerenin (3-hydroxy-3-methylglutarylbetanin) were isolated from purple pitaya (Hylocereus polyrhizus [Weber] Britton & Rose) juice, and their degradation products generated by heating at 85°C were subsequently monitored by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry. Thermal degradation of phyllocactin and hylocerenin in purified solution excluding the alleged protective effects by the juice matrix is reported for the first time. Betanin was predominantly degraded by hydrolytic cleavage, while decarboxylation and dehydrogenation were of minor relevance. In contrast, hylocerenin showed a strong tendency to decarboxylation and dehydrogenation, hydrolytic cleavage of the aldimine bond occurring secondarily. Phyllocactin degradation was most complex because of additional decarboxylation of the malonic acid moiety as well as generation and subsequent degradation of betanin due to phyllocactin demalonylation. Upon prolonged heating, all betacyanins under observation formed degradation products characterized by an additional double bond at C2C3. Hydrolytic cleavage of the aldimine bond of phyllocactin and hylocerenin yielded previously unknown acylated cyclo -dopa derivatives traceable by positive ionization, while application of ESI(,) facilitated the detection of a glycosylated aminopropanal derivative and dopamine, which have never been described before as betanin degradation products. Copyright © 2005 John Wiley & Sons, Ltd. [source] Structure of HsaD, a steroid-degrading hydrolase, from Mycobacterium tuberculosisACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 1 2008Nathan Lack Tuberculosis is a major cause of death worldwide. Understanding of the pathogenicity of Mycobacterium tuberculosis has been advanced by gene analysis and has led to the identification of genes that are important for intracellular survival in macrophages. One of these genes encodes HsaD, a meta -cleavage product (MCP) hydrolase that catalyzes the hydrolytic cleavage of a carbon,carbon bond in cholesterol metabolism. This paper describes the production of HsaD as a recombinant protein and, following crystallization, the determination of its three-dimensional structure to 2.35,Å resolution by X-ray crystallography at the Diamond Light Source in Oxfordshire, England. To the authors' knowledge, this study constitutes the first report of a structure determined at the new synchrotron facility. The volume of the active-site cleft of the HsaD enzyme is more than double the corresponding active-site volumes of related MCP hydrolases involved in the catabolism of aromatic compounds, consistent with the specificity of HsaD for steroids such as cholesterol. Knowledge of the structure of the enzyme facilitates the design of inhibitors. [source] | ||||||||||