The Schmidt reaction of anthraquinones

1982 ◽  
Vol 60 (5) ◽  
pp. 624-628 ◽  
Author(s):  
Cecily A. Flemming ◽  
Sham S. Gandhi ◽  
Martin S. Gibson ◽  
Edward H. Ruediger
Keyword(s):  
Sulfuric Acid ◽  
Amino Acid ◽  
Methyl Ester ◽  
Benzoic Acid ◽  
Sodium Azide ◽  
Schmidt Reaction ◽  
Direct Treatment ◽  
Hydrolysis Of

Schmidt reaction (sodium azide/sulfuric acid) of 1,5- and of 1,8-dichloroanthraquinones gives, in each case, both of the theoretically possible lactams (2,3,5,6-dibenzoazepin-4,7-diones). Two of the four theoretically possible lactams have been identified from Schmidt reaction of 1- and 2-chloroanthraquinones respectively. Methods used include: (a) preferential hydrolysis of one lactam and identification of the isomeric aminoanthraquinone formed on cyclodehydration of the resulting amino acid; (b) identification of the isomeric aminoanthraquinone(s) formed on direct treatment of a lactam (or mixture of lactams) by sulfuric acid; (c) cleavage by potassium tert-butoxide of the amino acid formed by preferential hydrolysis of one lactam and identification of the resulting benzoic acid as its methyl ester.

Oxidation of p–xylene to terephthalic acid in benzoic acid and methyl ester of p–toluic acid

1987 ◽  
Vol 52 (9) ◽  
pp. 2241-2247 ◽  
Author(s):  
Milan Hronec ◽  
František Masarovič ◽  
Zuzana Cvengrošová ◽  
Ján Ilavský
Keyword(s):  
Methyl Ester ◽  
Benzoic Acid ◽  
Terephthalic Acid ◽  
Cobalt Catalyst ◽  
Peroxy Radicals ◽  
Pyridine Ligands ◽  
Hydrolysis Of

The oxidation of p-xylene to terephthalic acid has been studied at 130 to 190 °C, using benzoic acid and methyl ester of p-toluic acid as the solvent. It was found that the solvent affects strongly the activity of the cobalt catalyst which effect is dependent on the presence of bromide and pyridine ligands. In the methyl ester of p-toluic acid as the solvent, cobalt-bromide catalysts induce also hydrolysis of the methyl ester which proceeds parallelly to the oxidation of p-xylene. The activating effect of bromide and pyridine ligands results from their effect on the rate of the reaction of peroxy radicals with the catalyst in the propagation step and from their effect on the rate of consecutive oxidation of p-toluic acid to terephthalic acid.

scholarly journals Synthesis and Characterization of New Thioxanthone Derivatives

2013 ◽  
Vol 10 (3) ◽  
pp. 724-735
Author(s):  
Baghdad Science Journal
Keyword(s):  
Sulfuric Acid ◽  
Benzoic Acid ◽  
Sodium Azide ◽  
Aromatic Amines ◽  
Chlorosulfonic Acid ◽  
Starting Material ◽  
Phosphorus Compounds ◽  
Synthesis And Characterization

This work comprises the synthesis of new thioxanthone derivatives containing C-substituted thioxanthone. To obtain these derivatives, the o-mercapto benzoic acid was chosen as the starting material, which was reacted with dry benzene in sulfuric acid (98 %) to produce the thioxanthone (1). The 2,7-(disulfonyl phosphine imine) thioxanthone (4-8) were prepared from reaction of compound (1) with chlorosulfonic acid gave 2,7-(disulfonyl chloride) thioxanthone (2). Treatment of (2) with sodium azide to produce 2,7-(disulfonyl azide) thioxanthone (3). Condensation of (3) with phosphorus compounds afforded compounds (4-8). The 2,7-(disulfonamide) thioxanthone (9-21) was obtained when compound (2) condensed with different aromatic amines, it gave the expected amides (9-21).

The stereospecificity of subtilisin BPN′ towards 1-keto-3-carbomethoxy-1,2,3,4-tetrahydroisoquinoline

1969 ◽  
Vol 47 (10) ◽  
pp. 985-987 ◽  
Author(s):  
Hermann Dugas
Keyword(s):  
Amino Acid ◽  
Methyl Ester ◽  
Active Site ◽  
Kinetic Constants ◽  
Neutral Amino Acid ◽  
Amino Acid Esters ◽  
Open Chain ◽  
Hydrolysis Of ◽  
Acid Esters ◽  
Chain Ester

Like α-chymotrypsin, subtilisin BPN′ reverses its normal stereospecificity when 1-keto-3-carbomethoxy-1,2,3,4-tetrahydroisoquinoline is the substrate; the D-isomer is hydrolyzed readily, the L-isomer is not. However, the enzyme retains its normal stereospecificity when the related open-chain ester N-benzoyl-alanine methyl ester is the substrate; the kinetic constants for hydrolysis of the L-isomer are comparable to those for hydrolysis of other neutral amino acid esters. These results suggest that the stereochemical requirements at the active site of subtilisin BPN′ are similar to those of α-chymotrypsin.

LYTIC ENZYMES OF SORANGIUM SP.: A COMPARISON OF THE PROTEOLYTIC PROPERTIES OF THE α- AND β-LYTIC PROTEASES

1965 ◽  
Vol 43 (12) ◽  
pp. 1961-1970 ◽  
Author(s):  
D. R. Whitaker ◽  
C. Roy ◽  
C. S. Tsai ◽  
L. Jurášek
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Methyl Ester ◽  
Esterase Activity ◽  
The Other ◽  
Carboxyl Group ◽  
Lytic Enzymes ◽  
Amidase Activity ◽  
A Chain ◽  
Hydrolysis Of

The proteolytic properties of the α- and β-lytic proteases of a species of Sorangium were compared. Neither enzyme showed evidence of aminopeptidase, carboxypeptidase, or amidase activity in tests with a series of peptides and substituted amino acids at pH 5.2, 7.2, and 9.0. Neither enzyme showed evidence of esterase activity towards N-benzoyl-L-arginine methyl ester at pH 6.8. Hydrolysis of the A chain of oxidized insulin at pH 9 slows down markedly when the α-enzyme has cleaved the chain once; the initial fast cleavage can take place at linkages between residues 9 and 10, 10 and 11, and 12 and 13; more slowly cleaved linkages are between residues 3 and 4, and 8 and 9. Hydrolysis of the B chain by the α-enzyme at pH 9 is still faster and slows down when the chain has been cleaved twice. One fast cleavage is at the linkage between residues 18 and 19; the other can take place at the linkages between residues 12 and 13, and 14 and 15; more slowly cleaved linkages are between residues 8 and 9, 9 and 10, and 15 and 16. Under the conditions tested, the β-enzyme does not hydrolyze the A chain appreciably at pH 9. It cleaves the B chain rapidly at the linkage between residues 23 and 24 and more slowly at linkages between residues 18 and 19. The linkages split by both enzymes are those which involve the carboxyl group of a neutral amino acid.

Azatropolones. Part II. The Schmidt Reaction of 2-Methoxy-5-methylbenzoquinone

1974 ◽  
Vol 52 (19) ◽  
pp. 3327-3330 ◽  
Author(s):  
Colin G. Hughes ◽  
Errol G. Lewars ◽  
Alun H. Rees
Keyword(s):  
Sulfuric Acid ◽  
Carboxylic Acid ◽  
Sodium Azide ◽  
Phosphorus Oxychloride ◽  
Schmidt Reaction ◽  
Ring Contraction

2-Methoxy-5-methylbenzoquinone undergoes reaction with sodium azide in sulfuric acid to give (a) 3-hydroxy-6-methyl-1H-azepin-2,5-dione, which undergoes ring contraction with base to give 5-methyl-4-pyridone-2-carboxylic acid; (b) 4-methoxy-7-methyl-1H-azepin-2,5-dione, which reacts with phosphorus oxychloride to give methyl 2-chloro-6-methylpyridine-4-carboxylate, not 2-chloro-4-methoxy-7-methyl-5H-azepin-5-one; (c) 7-methoxy-4-methyl-1H-azepin-2,5-dione. The reactions of these compounds are discussed and the evidence for their structures is presented.

Destruction of intracellular and isolated Leishmania mexicana amazonensis amastigotes by amino acid amides

Parasitology ◽  
1988 ◽  
Vol 96 (2) ◽  
pp. 289-296 ◽  
Author(s):  
M. Rabinovitch ◽  
V. Zilberfarb
Keyword(s):  
Amino Acid ◽  
Methyl Ester ◽  
Methyl Esters ◽  
Hydrolytic Enzymes ◽  
Amino Acid Esters ◽  
Leishmania Mexicana ◽  
Acid Methyl ◽  
Hydrolysis Of ◽  
Acid Esters ◽  
Amino Acid Methyl Esters

SummaryL-amino acid esters such as leucine methyl ester (Leu-OMe) destroy Leishmania mexicana amazonensis amastigotes by a mechanism which may involve hydrolysis of the compounds by parasite enzymes. Moreover, several esters (e.g. Ile-OMe) prevent the killing of parasites by Leu-OMe, perhaps by inhibition of the hydrolytic enzymes. We show here that certain amino acid amides are also leishmanicidal. Killing of Leishmania within macrophages was assessed microscopically, and that of isolated amastigotes was measured by reduction of the tetrazolium MTT. Amino acid amides were generally less active than the methyl esters and several were more toxic to the macrophages, as determined by inspection of Giemsa-stained preparations. Ranks of activity of the amides on isolated amastigotes were Trp > Leu > Phe > Met > Tyr. The amides of Ala, Gly, Val, Ile, His and D-Leu were inactive. This pattern of activity is similar to that of amino acid methyl esters. Ile-NH2 and a few other amides protected intracellular as well as isolated parasites from killing by Leu-OMe. Conversely, Ile-OMe reduced the toxicity of Leu-NH2 for isolated amastigotes. None of the esters or amides assayed prevented the destruction of Leishmania by Trp-NH2. The results are compatible with the view that amino acid esters and amides may be recognized by the same or similar parasite enzymes.

scholarly journals The substrate specificity of thermomycolase, an extracellular serine proteinase from the thermophilic fungus Malbranchea pulchella var. sulfurea

1975 ◽  
Vol 151 (3) ◽  
pp. 527-542 ◽  
Author(s):  
K J Stevenson ◽  
G M Gaucher
Keyword(s):  
Amino Acid ◽  
Methyl Ester ◽  
Congo Red ◽  
Serine Proteinase ◽  
Amino Acid Residues ◽  
Peptide Bonds ◽  
Native Collagen ◽  
Hydrophobic Binding ◽  
Malbranchea Pulchella ◽  
Hydrolysis Of

The specificity of thermomycolase toward glucagon and the oxidized A and B chains of insulin was investigated. Extensive digestion of glucagon occurred when conducted at pH 7.0 and 45 ° C for 40 min, whereas hydrolysis of only three peptide bonds occurred at pH 7.0 and 28 ° C for 5 min. A similar situation was observed for the oxidized B chain of insulin, which exhibited only a single major cleavage after 5 min at 25 ° C. No well-defined specificity for particular amino acid residues was evident, but ready hydrolysis of peptide bonds occurred within sequences containing non-polar residues. This endoproteinase must therefore possess an extended hydrophobic binding site for polypeptides. Thermomycolase hydrolysed acetylalanylalanylalanine methyl ester and elastin-Congo Red at 22 and 8.5 times the rate of porcine elastase respectively. A limited degradation of native collagen and significant hydrolysis of benzyloxycarbonyl-Gly-Pro-Leu-Gly-Pro were suggestive of some collagenase-like activity. No keratinase activity was apparent.

scholarly journals The structure and mechanism of stem bromelain. Evaluation of the homogeneity of purified stem bromelain, determination of the molecular weight and kinetic analysis of the bromelain-catalysed hydrolysis of N-benzyloxycarbonyl-l-phenylalanyl-l-serine methyl ester

1974 ◽  
Vol 143 (3) ◽  
pp. 575-586 ◽  
Author(s):  
Christopher W. Wharton
Keyword(s):  
Molecular Weight ◽  
Amino Acid ◽  
Methyl Ester ◽  
Gel Electrophoresis ◽  
Ph Dependence ◽  
Polyacrylamide Gel Electrophoresis ◽  
Terminal Amino Acid ◽  
Terminal Amino ◽  
Stem Bromelain ◽  
Hydrolysis Of

1. Purified stem bromelain (EC 3.4.22.4) was eluted from Sephadex G-100 as a single peak. The specific activity across the elution peak was approximately constant towards p-nitrophenyl hippurate but increased with elution volume with N2-benzoyl-l-arginine ethyl ester as substrate. 2. The apparent molecular weight, determined by elution analysis on Sephadex G-100, is 22500±1500, an anomalously low value. 3. Purified stem bromelain was eluted from CM-cellulose CM-32 as a single peak and behaved as a single species during column electrophoresis on Sephadex G-100. 4. Purified stem bromelain migrates as a single band during polyacrylamide-gel electrophoresis under a wide variety of conditions. 5. The molecular weight determined by polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate is 28500±1000. 6. Sedimentation-velocity and equilibrium-ultracentrifugation experiments, under a variety of conditions, indicate that bromelain is an apparently homogeneous single peptide chain of mol.wt. 28400±1400. 7. The N-terminal amino acid composition is 0.64±0.04mol of valine and 0.36±0.04mol of alanine per mol of enzyme of mol.wt. 28500. (The amino acid recovery of the cyanate N-terminal amino acid analysis was standardized by inclusion of carbamoyl-norleucine at the cyclization stage.) 8. The pH-dependence of the Michaelis parameters of the bromelain-catalysed hydrolysis of N-benzyloxycarbonyl-l-phenylalanyl-l-serine methyl ester was determined. 9. The magnitude and pH-dependence of the Michaelis parameters have been interpreted in terms of the mechanism of the enzyme. 10. The enzyme is able to bind N-benzyloxycarbonyl-l-phenylalanyl-l-serine methyl ester relatively strongly but seems unable to make use of the binding energy to promote catalysis.

scholarly journals INHIBITION OF THE d-AMINO ACID OXIDASE BY BENZOIC ACID

1941 ◽  
Vol 138 (2) ◽  
pp. 507-512 ◽  
Author(s):  
J. Raymond Klein ◽  
Henry Kamin
Keyword(s):  
Amino Acid ◽  
Benzoic Acid ◽  
Acid Oxidase ◽  
Amino Acid Oxidase
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