C hydrolytic cleavage

Deformylation of the cleavage product yields L-kynurenine, which is the substrate for hydrolytic C—C cleavage by kynureninase, a pyridoxal 5 -phosphate-dependent enzyme. The a-amino group of L-kynurenine is attached to the PLP cofactor, and deprotonation of the a-carbon forms a ketimine linkage, which provides an electron sink to assist C-C hydrolytic cleavage, as shown in Figure 27. 

C. Hydrolytic Cleavage of RNA, DNA, and Simple Phosphodiesters by Metal Complexes... 

Fig. 4 Degradation of PEG cystine polyester at 37°C Hydrolytic cleavage of ester moieties at different pH values (solid symbols). Reduction of disulfides at pH 5.5 (cqch = 5 mmol) (diamonds). From [89]. Copyright Wiley-VCH. Reproduced with permission...

Hydrolases. Enzymes catalysing the hydrolytic cleavage ofC —O, C —N and C —C bonds. The systematic name always includes hydrolase but the recommended name is often formed by the addition of ase to the substrate. Examples are esterases, glucosidases, peptidases, proteinases, phospholipases. Other bonds may be cleaved besides those cited, e.g. during the action of sulphatases and phosphatases. 

The small tendency of oxaziridines to undergo hydrolytic C—O cleavage is underlined by the observation that oxaziridine (52) in a mixture of acid and 0-labeled water yields up to 50% labeled hydroxylamine. NH transfer to water successfully competes with hydrolysis (B-67MI50800). 

The hydrogeh atom bound to the amide nitrogen in 15 is rather acidic and it can be easily removed as a proton in the presence of some competent base. Naturally, such an event would afford a delocalized anion, a nucleophilic species, which could attack the proximal epoxide at position 16 in an intramolecular fashion to give the desired azabicyclo[3.2.1]octanol framework. In the event, when a solution of 15 in benzene is treated with sodium hydride at 100 °C, the processes just outlined do in fact take place and intermediate 14 is obtained after hydrolytic cleavage of the trifluoroacetyl group with potassium hydroxide. The formation of azabi-cyclo[3.2.1]octanol 14 in an overall yield of 43% from enone 16 underscores the efficiency of Overman s route to this heavily functionalized bicycle. 

Hydrolases catalyze the hydrolytic cleavage of C—C, C—O, C—N, P—O, and certain other bonds, including acid anhydride bonds. 

This study reports on the production of pectic enzymes and partial characterization of polygalacturonases produced by Candida boidinii. Candida boidinii belongs to the so called methylotrophic yeasts with famous utilization of methanol. Pectin, the natural substrate of pectic enzymes complex, can serve for microorganisms as a C - source by two different ways after deesterification with pectinesterase as methanol and after hydrolytic cleavage with... 

Hydrolytic cleavage of the glycosidic bond holding the DNA bases to the sugar-phosphate backbone is typically a very slow process under physiological conditions (pH 7.4 37°C). Loss of the pyrimidine bases cytosine and thymine occurs with a rate constant of 1.5 X 10 s (ty2 = 14,700 years), while loss of the purine bases guanine and adenine proceeds slightly faster, with a rate constant of 3.0 X... 

Kostic et al. recently reported the use of various palladium(II) aqua complexes as catalysts for the hydration of nitriles.456 crossrefil. 34 Reactivity of coordination These complexes, some of which are shown in Figure 36, also catalyze hydrolytic cleavage of peptides, decomposition of urea to carbon dioxide and ammonia, and alcoholysis of urea to ammonia and various carbamate esters.420-424, 427,429,456,457 Qggj-jy palladium(II) aqua complexes are versatile catalysts for hydrolytic reactions. Their catalytic properties arise from the presence of labile water or other solvent ligands which can be displaced by a substrate. In many cases the coordinated substrate becomes activated toward nucleophilic additions of water/hydroxide or alcohols. New palladium(II) complexes cis-[Pd(dtod)Cl2] and c - Pd(dtod)(sol)2]2+ contain the bidentate ligand 3,6-dithiaoctane-l,8-diol (dtod) and unidentate ligands, chloride anions, or the solvent (sol) molecules. The latter complex is an efficient catalyst for the hydration and methanolysis of nitriles, reactions shown in Equation (3) 435... 

Based on the composition of the C18 family of cutin monomers we postulated that oleic acid would be > hydroxy la ted first, followed by epoxidation of the double bond at C-9 followed by the hydrolytic cleavage of the oxirane to yield 9,10,18-trihydroxy acid. This postulate was experimentally verified by the demonstration of specific incorporation of exogenous 18-hydroxyoleic acid into 18-hydroxy-9,10-epoxy C18 acid in grape berry skin slices and apple fruit skin disks, and incorporation of exogenous labeled 18-hydroxy-9,10-epoxy C18 acid into 9,10,18-trihydroxy C18 acid of cutin in apple fruit skin slices [61]. 

In terms of economical synthetic approaches to indoles, the synthesis of this heterocycle from anilines and trialkylammonium chlorides was effected in an aqueous medium (H20-dioxane) at 180°C in the presence of a catalytic amount of ruthenium(III) chloride hydrate and triphenylphosphine together with tin(II)chloride <00TL1811>. Muchowski devised a novel synthetic route to indole-4-carboxaldehydes and 4-acetylindoles 86 via hydrolytic cleavage of W-alkyl-5-aminoisoquinolinium salts 85 to homophthaldehyde derivatives upon heating in a two phase alkyl acetate-water system containing an excess of a 2 1 sodium bisulfite-sodium sulfite mixture <00JHC1293>. 

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