Diketo Compounds Research Articles

A novel efficient enzyme-immobilization reaction on NH2 polymers by means of L-ascorbic acid.

A new enzyme-immobilization reaction by means of L-ascorbic acid (ASA) is described using NH(2) polymers based on cellulose or poly(vinyl alcohol) with the example of oxidoreductase enzymes. In this way, enzyme proteins such as glucose oxidase (GOD), glutamate oxidase, lactate oxidase, urate oxidase and peroxidase can be covalently fixed with a high surface loading to ultrathin and transparent NH(2)-polymer films if their surfaces are previously treated with an ASA solution, in, for example, N,N-dimethyl acetamide, DMSO or methanol. ASA then obviously reacts like a diketo compound with amino groups of the NH(2)-polymer film and enzyme protein, forming dehydroascorbic acid derivatives with neighbouring Schiff's-base structures. In a subsequent fragmentation reaction, the latter presumably form stable oxalic acid diamide derivatives as coupling structures between enzyme protein and NH(2)-polymer film, as suggested by results from investigations of the ASA reaction with n-butylamine. The immobilized enzymes can be stored at 4 degrees C in bidistilled water for at least 1 month without becoming detached from the NH(2)-polymer film and without diminished enzyme activity. The apparent K(m) values of the immobilized enzymes are in part clearly smaller than those of the dissolved enzymes or those found in other immobilization processes such as the diazo coupling or the bifunctional glutardialdehyde reaction. For example, the K(m) value of the immobilized GOD with different NH(2) polymers as the matrix structure is smaller by a factor of approx. 20 than that of the dissolved enzyme.

Guanosine 5‘-O-[S-(4-bromo-2,3-dioxobutyl)]thiophosphate and adenosine 5‘-O-[S-(4-bromo-2,3-dioxobutyl)]thiophosphate. New nucleotide affinity labels which react with rabbit muscle pyruvate kinase.

Three new reactive nucleotide analogues with bromo-keto substituents adjacent to a thiophosphate have been synthesized. Guanosine 5'-O-[S-(4-bromo-2,3-dioxobutyl)]thiophosphate (GMPS-BDB), reacts covalently with rabbit muscle pyruvate kinase with complete inactivation and incorporation of 1.8 mol of reagent/mol of enzyme subunit. By contrast, the mono-keto compound, guanosine 5'-O-[S-(3-bromo-2-oxopropyl)]thiophosphate (GMPS-BOP), causes no loss of pyruvate kinase activity. When the analogous adenosyl nucleotide derivatives are incubated with pyruvate kinase, the di-keto compound, adenosine 5'-O-[S-(4-bromo-2,3-dioxobutyl)]thiophosphate (AMPS-BDB), rapidly effects inactivation, whereas the mono-keto compound, adenosine 5'-O-[S-(3-bromo-2-oxopropyl)]thiophosphate (AMPS-BOP), causes no loss of activity. Complete protection against inactivation by GMPS-BDB is provided by phosphoenolpyruvate in the presence of K+ and Mn2+ and the amount of reagent incorporated (0.9 mol/reagent/mol subunit) is reduced to half that observed in the absence of protectants. Gas-phase sequencing of the tryptic peptides purified from inactive GMPS-BDB or AMPS-BDB-modified enzyme gave the cysteine-labeled peptides: C151DENILWLDYK161, and N162IC164K165 as the two major peptide products, with a smaller amount of N43TGIIC48TIGPASR55. Reaction in the presence of the protectants PEP, K+, and Mn2+ yielded Cys164 as the only labeled residue, indicating that inactivation is primarily due to modification of Cys151. We propose that GMPS-BDB (or AMPS-BDB), which may exist in enolized form in aqueous solution, functions as a reactive analogue of phosphoenolpyruvate and GDP (ADP) to target Cys151 in the active site of pyruvate kinase.

ChemInform Abstract: Palladium‐Catalyzed Carbonyl Allylation of Diketo Compounds by Allylic Alcohols with SnCl2.

AbstractUsing 1,3‐dimethyl‐2‐imidazolidinone as the solvent, the 1,2‐diketones (I) undergo palladium‐catalyzed allylation with allyl alcohol in the presence of tin dichloride, yielding mainly the diallylation products (IV) and/or (V).

Palladium-Catalyzed Carbonyl Allylation of Diketo Compounds by Allylic Alcohols with SnCl2

Abstract Palladium-catalyzed diallylation of 1,2-diketones and 1,2-ketoaldehyde by allyl alcohol with SnCl2 in DMI was accelerated and proceeded diastereoselectively thanks to a chelation of a carbonyl group to Sn(IV) (tin alkoxide) in the corresponding monoallylated intermediates.

ChemInform Abstract: Tin(IV) Chloride Promoted vs. Metal β‐Carbonylenolate Catalyzed Reactions of β‐Dicarbonyls with Nitriles.

AbstractThe diketo compounds (Ia) and (Ib) undergo SnCl4‐promoted reaction with activated nitriles (II) (R3: COPh, COOEt, CCl3) to give mixtures of the enamino diketo compounds (III) and their deacetylated derivatives (IV).

Myeloperoxidase-catalyzed incorporation of amines into proteins: role of hypochlorous acid and dichloramines.

Myeloperoxidase-catalyzed oxidation of chloride (Cl-) to hypochlorous acid (HOCl) resulted in formation of mono- and dichloramine derivatives (RNHCl and RNCl2) of primary amines. The RNCl2 derivatives could undergo a reaction that resulted in incorporation of the R moiety into proteins. The probable mechanism was attack of RNCl2 or an intermediate formed in the decomposition of RNCl2 on histidine, tyrosine, and cystine residues and on lysine residues at high pH. Incorporation of radioactivity from labeled amines into stable, high molecular weight derivatives of proteins was measured by acid or acetone precipitation and by gel chromatography and electrophoresis. Whereas formation of RNCl2 was favored at low pH, the subsequent incorporation reaction was favored at high pH. Up to several hours were required for the maximum amount of incorporation, which was less than 10% of the label in RNCl2. For the amines tested, incorporation was in the order histamine greater than 1,2-diaminoethane greater than putrescine greater than taurine greater than lysine greater than glucosamine greater than leucine greater than methylamine. Initiation of the reaction required HOCl, and oxidized forms of bromide, iodide, or thiocyanate did not substitute. Inhibitors of incorporation fell into three classes. First, ammonia or amines competed with the labeled amine for reaction with HOCl, so that larger amounts of HOCl were required. Second, readily oxidized substances such as sulfhydryl or diketo compounds or thioethers (methionine) reduced RNCl2. Third, certain compounds competed with protein as the acceptor for the incorporation reaction. The amount required to block incorporation into protein depended on protein concentration. Among these inhibitors were imidazole compounds (histidine), phenols (tyrosine), and disulfides (glutathione disulfide, GSSG). Low yields of derivatives of histidine, tyrosine, and GSSG were detected by thin-layer chromatography. Acid-precipitable derivatives were obtained by reacting RNCl2 with polyhistidine or polytyrosine, and to a lesser extent with polylysine at high pH, but not with other poly(amino acids). Precipitable derivatives were also obtained by incubating MPO-containing extracts from leukocyte granules with hydrogen peroxide, Cl-, and labeled amines. The extracts were found to have a high content of substances with primary amino groups, which competed for incorporation. The results account for oxidative incorporation of amines into proteins in leukocytes and provide evidence that HOCl and nitrogen-chlorine (N-Cl) derivatives are formed in these cells. The characteristics of the incorporation reaction suggest that it would not contribute significantly to the antimicrobial activity of myeloperoxidase (MPO). Nevertheless, the reaction may provide a sensitive method for studying MPO action in vivo.

Reaction of 2‐carboxy‐1‐methylindole‐3‐acetic acid anhydride with amines and with S‐methylisothiosemicarbazide

Abstract2‐Carboxy‐1‐alkylindole‐3‐acetic acid anhydrides (I) condensed with S‐methylisothiosemicarbazide in DMF to form 5,11‐dihydro‐6‐methyl‐2‐methylthioindolo[3′,2′:4,5]pyrido[1,2‐b]‐s‐triazol‐5‐one (II). Compound II underwent ring opening on refluxing with sodium hydroxide solution to give IV. The anhydride I reacted with primary amines in benzene to give 2‐carboxy‐1‐alkylindole‐3‐acetanilide derivatives (VI) which yielded l‐methylindole‐3‐acetic acid by decarboxylation followed by hydrolysis. Compound II oxidised to the diketo compound X which could be prepared by the hydrolysis of the azomethine derivative IX with acetic acid‐hydrochloric acid mixture. Compound II reacted with benzyl chloride to yield the dibenzyl derivative XII, condensed with p‐chlorobenzaldehyde to form the 11‐p‐chlorobenzylidene derivative XI and coupled with arenediazonium salt to give the 11‐arylhydrazone derivatives XIII.

Preparation of, and alkylation of enolate anions with, dimethyl 3-bromo-2 ethoxypropenylphosphonate. An efficient, convergent synthesis of 2-cyclo-penten-1-ones

The alkylation of enolate anions with dimethyl 3-bromo-2-ethoxypropenylphosphonate, followed by acid hydrolysis of the resultant products, affords diketo phosphonate compounds which can be cyclized efficiently to give the corresponding 2-cyclopenten-1-ones. This overall five-membered ring annelation process can be carried out without affecting acid-labile functional groups (e.g. ketal) in the enolate substrate.

The Chemistry of Phenylcyclobutenediones

AbstractPhenylcyclobutenediones are easily obtainable and very stable. Depending on the nature of the substituent R in position 3, they may be formally regarded as vinylogous carboxylic acid derivatives (Rhalogen, OCH3, OH, SH) or as α,β‐unsaturated diketo compounds (RH, alkyl, aryl). Their behavior in reactions justifies this approach. Ring contraction, ring expansion, and ring cleavage reactions are described.

2,5-diketogluconate formation by Chromobacterium.

Chromobacterium lividum oxidizes gluconate to 2,5-diketogluconate via 2-ketogluconate. The conversion by either growing or resting cells proceeds best in an aerated medium at pH 5.9. The yield is nearly 50%. Diketogluconate is not further decomposed. The preparation of chromatographically pure diketogluconate using eitherChromobacterium orGluconobacter is described. Several properties of the diketo compound are described.

Zur theorie der α-ketosäuren : Beziehungen zwischen struktur und UV-Spektren von α-ketosäuren und verwandten α-dicarbonylverbindungen

In homopolar solvents α-keto acids form a stable proton chelate between the carboxyl and α-carbonyl groups. This chelate causes a major bathochrome shift of the n-π*-bands of the α-carbonyl group as compared to the spectrum of the non-chelated molecule, and moreover it shows a remarkable vibrational band structure. The UV spectra of α-keto acid amides also suggest an intramolecular -NH⋯OC interaction. A study of the action of the alkyl group on the n-π*-bands in compounds of the type R 1COCOR 2 (R 1 = Alkyl; R 2 = OH, NH 2 and CH 3) shows that methyl diketo compounds (CH 3COCOR 2) occupy a special position, as hyperconjugation is possible.

Electron-affinic sensitization. I. A structural basis for chemical radiosensitizers in bacteria.

The bacterium Serratia marcescens has been used as a test system for demon- strating the radiosensitizing properties of a class of electron-affinic organic compounds. These include: unsaturated diesters and diketo compounds, mono-, di- and triketohydrindene (indanetrione), derivatives of pyruvic acid, quinones and several miscellaneous compounds. With few exceptions, the sensitization is restricted to anoxic systems. An electron-transfer mechanism, involving interaction of the sensitizer with a charged intermediate produced by direct energy absorption in a target molecule, is proposed as the basis of a model for radiosensitization. Bridges (1969) has discussed radiosensitization at different levels of biological complexity and has made a critical evaluation of the various mechanisms pro- posed in the literature. In this paper, an account is given of the development of a physico-chemical model for cellular radiosensitization based on the electron-affinic properties of the dose-modifying agents. In a previous publication (Adams and Dewey 1963), a mechanism was suggested in which the sensitizing effects of N-ethylmaleimide, diacetyl and benzophenone were attributed to their ability to act as electron-transport agents in enhancing the damaging effects of hydrated electrons produced by energy absorption in the aqueous component of the cell. Although this earlier model was empirically successful, in that it led to the characterization of most of the bacterial radiosensitizers discussed in this paper, it has serious limitations. An alternative model, also based directly on electron-affinity concepts, but more consistent with recent data, is therefore proposed in the discussion. However, since this mechanism was developed from the earlier hypothesis, a brief des- cription of the latter is included in this introduction. The main postulate of this model was that the sensitizing properties of N-ethylmaleimide were attributed to its ability to capture and stabilize a hydrated