THE USE OF HYDROGEN BROMIDE IN ACETIC ACID FOR THE REMOVAL OF CARBOBENZOXY GROUPS AND BENZYL ESTERS OF PEPTIDE DERIVATIVES1

1954 ◽  
Vol 19 (1) ◽  
pp. 62-66 ◽  
Author(s):  
DOV BEN-ISHAI
Keyword(s):  
Acetic Acid ◽  
Hydrogen Bromide ◽  
Benzyl Esters

Comparative acidic cleavage experiments with methyl-substituted benzyl esters of amino acids

1967 ◽  
Vol 20 (10) ◽  
pp. 2243 ◽  
Author(s):  
FHC Stewart
Keyword(s):  
Amino Acids ◽  
Acetic Acid ◽  
Amino Acid ◽  
Solid Phase ◽  
Hydrogen Bromide ◽  
Solid Phase Peptide Synthesis ◽  
Amino Acid Derivatives ◽  
Methyl Substitution ◽  
Benzyl Esters ◽  
Layer Chromatography

The action of trifluoroacetic acid and hydrogen bromide in acetic acid, respectively, on the benzyl, p-methylbenzyl, 2,4,6-trimethylbenzyl, and penta-methylbenzyl esters of some amino acid derivatives has been investigated by thin-layer chromatography. Methyl substitution greatly enhances the lability of the ester groups. The possible bearing of the results on solid-phase peptide synthesis is discussed.

The use of 2,4,6-trimethylbenzyl esters in peptide synthesis

1966 ◽  
Vol 19 (6) ◽  
pp. 1067 ◽  
Author(s):  
FHC Stewart
Keyword(s):  
Acetic Acid ◽  
Hydrogen Chloride ◽  
Peptide Synthesis ◽  
Hydrogen Bromide ◽  
Ester Group ◽  
Protecting Groups ◽  
Reaction Conditions ◽  
Model Experiments ◽  
Benzyl Esters

Model experiments with the 2,4,6-trimethylbenzyl esters of N-acylamino acids have shown that this ester group is cleaved by hydrogen bromide in acetic acid under reaction conditions which do not affect benzyl esters appreciably, but which result in removal of benzyloxycarbonyl amino-protecting groups. 2,4,6-Trimethyl- benzyl esters, however, are unaffected by methanolic hydrogen chloride under the conditions used to cleave o-nitrophenylsulphenyl and trityl protecting groups. These selective differences have been utilized for the synthesis of various benzyloxycarbonyl peptide 2,4,6-trimethylbenzyl esters up to the hexapeptide level. Some of these derivatives have been converted into the corresponding free peptides by the action of hydrogen bromide in acetic acid. The 2,4,6-trimethylbenzyl group is more readily cleaved by hydrogen bromide than p-nitrobenzyloxycarbonyl and the possible application of this situation to peptide synthesis is considered.

The synthesis of norbornanes with functionalized carbon substituents at a bridgehead. 1-(3-Oxonorborn-1-yl)ethanone and 1-(3-oxonorborn-1-yl)-2-propanone

1992 ◽  
Vol 70 (5) ◽  
pp. 1492-1505 ◽  
Author(s):  
Peter Yates ◽  
Magdy Kaldas
Keyword(s):  
Acetic Acid ◽  
Carboxylic Acid ◽  
Hydrogen Bromide ◽  
Tertiary Alcohol ◽  
Ethyl Bromoacetate ◽  
Second Molar ◽  
Molar Equivalent ◽  
Acid Lactone ◽  
Basic Hydrolysis ◽  
Hydrolysis Of

Treatment of 2-norobornene-1-carboxylic acid (7) with one equivalent of methyllithium in ether followed by a second molar equivalent after dilution with tetrahydrofuran gave 1-(norborn-2-en-lyl)ethanone (10) and only a trace of the tertiary alcohol 11. Reaction of 7 with formic acid followed by hydrolysis gave a 4:3 mixture of exo-3- and exo-2-hydroxynorbornane-1-carboxylic acid (16 and 17), whereas oxymercuration–demercuration gave only the exo-3-hydroxy isomer 16. Oxidation of 16 and 17 gave 3- and 2-oxonorbornane-1-carboxylic acid (27 and 29), respectively. Oxymercuration–demercuration of 10 gave exclusively 1-(exo-3-hydroxynorborn-1-yl)ethanone (30), which was also prepared by treatment of 16 with methyllithium in analogous fashion to that used for the conversion of 7 to 10. Oxidation of 30 gave 1-(3-oxonorborn-1-yl)ethanone (1). Dehydrobromination of exo-2-bromonorbornane-1-acetic acid and dehydration of 2-hydroxy-norbornane-2-acetic acid derivatives gave 1-(norborn-2-ylidene) acetic acid derivatives to the exclusion of norborn-2-ene-1 -acetic acid derivatives. Treatment of exo-5-acetyloxy-2-norobornanone (52) with ethyl bromoacetate and zinc gave ethyl exo-5-acetyloxy-2-hydroxynorbornane-(exo- and endo-2-acetate (53 and 54). Reaction of 53 with hydrogen bromide gave initially ethyl endo-3-acetyloxy-exo-6-bromonorbornane-1-acetate (59), which was subsequently converted to a mixture of 59 and its exo-3-acetyloxy epimer 61. Catalytic hydrogenation of this mixture gave a mixture of ethyl endo- and exo-3-acetyloxynorbornane-1 -acetate (62 and 63). Basic hydrolysis of this gave a mixture of the corresponding hydroxy acids, 70 and 71; the former was slowly converted to the latter at pH 5. Oxidation of the mixture of 70 and 71 gave 3-oxonorbornane-1-acetic acid (72). Treatment of the mixture with methyllithium as for 16 gave a mixture of 1-(endo- and exo-3-hydroxynorborn-1-yl)-2-propanone (73 and 74), which was oxidized to 1-(3-oxo-norborn-1-yl)-2-propanone (2). Reaction of exo-2-hydroxynorbornane-1-acetic acid lactone (75) with methyllithium in ether gave (1-(exo-2-hydroxynorborn-1-yl)-2-propanone (76), which on oxidation gave the 2-oxo isomer 78 of 2.

scholarly journals Fast-Hardening Foam: Fire and Explosion Prevention at Facilities with Hazardous Chemicals

2017 ◽  
Vol 6 (4) ◽  
pp. 56
Author(s):  
Gennady N. Kuprin ◽  
Denis S. Kuprin
Keyword(s):  
Acetic Acid ◽  
Hydrogen Chloride ◽  
Hydrogen Fluoride ◽  
Diesel Fuel ◽  
High Probability ◽  
Hydrogen Bromide ◽  
Screening Method ◽  
Hazardous Chemicals ◽  
Experimental Apparatus ◽  
Fire And Explosion

Analysis of the terroristic attacks in Siria, Afghanistan and other countries has shown high probability of the hazardous chemicals application by the terroristic groups. In the article the most catastrophic accidents which were connected with hazardous chemicals are described.That is why research and developments in the sphere of protection from hazardous chemicals are still actual.This article is dedicated to the new screening method of the spilled hazardous chemicals surface on the example of protection of the factories with these substances. Methodology, experimental apparatus, protective fast-hardening foam features, names of hazardous chemicals are shown.Test were made for such chemicals as: acetic acid, acetone, ammonia, bromine, chlorbenzene, chloroform, hydrogen bromide, hydrogen chloride, hexane, hydrazine, diesel fuel, dichlorethane, kerosene, toluene, phenol, hydrogen fluoride. Fantastic results were achieved in terms of isolating capability of the fast-hardening foam against evaporations of the pointed substances.

Peptide syntheses with the 2,4,6-trimethylbenzyl esters of L-asparagine and L-glutamine

1967 ◽  
Vol 20 (2) ◽  
pp. 365 ◽  
Author(s):  
FHC Stewart
Keyword(s):  
Acetic Acid ◽  
Amino Acid ◽  
Hydrogen Chloride ◽  
Hydrogen Bromide ◽  
Amino Acid Esters ◽  
Mild Conditions ◽  
Acid Esters

The 2,4,6-trimethylbenzyl esters of L-asparagine and L-glutamine have been obtained as the crystalline hydrochlorides by treatment of the o- nitrophenylsulphenyl amino acid esters with methanolic hydrogen chloride. These hydrochlorides were used in the synthesis of several benzyloxycarbonyl peptide 2,4,6-trimethylbenzyl esters, which were converted into the corresponding free peptides by the action of hydrogen bromide in acetic acid under mild conditions.

N-Methylamino Acids in Peptide Synthesis. III. Racemization during Deprotection by Saponification and Acidolysis

1973 ◽  
Vol 51 (15) ◽  
pp. 2555-2561 ◽  
Author(s):  
John R. McDermott ◽  
N. Leo Benoiton
Keyword(s):  
Acetic Acid ◽  
Sodium Hydroxide ◽  
Hydrogen Bromide ◽  
Aqueous Sodium Hydroxide ◽  
Acid Strength ◽  
Carboxyl Group ◽  
Aqueous Sodium ◽  
Aqueous Acid ◽  
Amino Acid Analyzer ◽  
Anhydrous Acetic Acid

The racemization of N-methylamino-acid derivatives in aqueous sodium hydroxide and hydrogen bromide in anhydrous acetic acid and other solvents has been investigated by determining the products of the reaction with an amino-acid analyzer after deprotection. Whereas MeIle-OMe, Z-MeIle, and the N-unmethylated derivatives were only slightly racemized ( <2%), Z-MeIle-OMe (18–24%), Z-Ala-MeLeu-OMe (22%), and Z-Ala-MeLeu-OBu′ (7%) were appreciably racemized by aqueous sodium hydroxide. It is suggested that these derivatives racemize because of the absence of an > N—H or carboxyl group whose ionization would suppress ionization of the neighboring α-C—H bond. Z-Melle and Z-Ala-MeLeu were substantially racemized (68% in 4 h and 34% in 1 h, respectively) by 5.6 N hydrogen bromide in acetic acid. The extent of racemization by acid varied with acid strength, polarity of solvent, and time. Incorporation of label into both isomers of Ala-MeLeu from a solution of the tritiated reagent established that ionization at the α-C—H bond had occurred. No racemization was caused by aqueous acid or by hydrogen chloride.

Reactions of N-substituted 2-aminopyridines with chloroacetyl chloride; Formation of a new series of heterocyclic betaines: 1-Substituted 4-chloromethyl-2-oxopyrido[1,2-a]pyrimidin-5-ium-3-olates

1989 ◽  
Vol 54 (5) ◽  
pp. 1376-1387 ◽  
Author(s):  
Hana Hulinská ◽  
Miloš Buděšínský ◽  
Jiří Holubek ◽  
Oluše Matoušová ◽  
Hana Frycová ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Sodium Borohydride ◽  
Nmr Spectra ◽  
Aqueous Ethanol ◽  
Hydrogen Bromide ◽  
Chloroacetyl Chloride ◽  
Gastric Lesions ◽  
Substitution Reactions ◽  
Reaction Compound ◽  
C Nmr

N-(2-Pyridyl)-2-chloroacetamide reacted with 1-methylpiperazine and gave the expected compound III. Attempts at preparing the N-substituted N-(2-pyridyl)-2-chloroacetamides by reactions of N-substituted 2-aminopyridines with chloroacetyl chloride in benzene in the presence of N,N-dimethylacetamide were negative and took an unexpected course. 2-Anilinopyridine and 2-(cyclohexylamino)pyridine afforded compounds which were identified by 1H and 13C NMR spectra as the heterocyclic betaines IVa and IVb. 2-(1-Butylamino)pyridine, 2-(benzylamino)pyridine and 2-(2-phenylethylamino)pyridine gave similarly compounds IVc-IVe. The chloromethyl compounds IVa-IVe underwent normal substitution reactions with 1-methylpiperazine and gave the methylpiperazino compounds Va-Ve. Attempts to reduce the betaines with sodium borohydride in aqueous ethanol proceeded in one case as the hydrogenolytic displacement of the chlorine atom with hydrogen (product VIa), in another case as ethanolysis (product VIIb). Formation of VIb by treatment of IVb with hydrogen bromide in boiling acetic acid is probably the result of a disproportionation reaction. Compound III (dimaleate VÚFB-17 103) was practically equipotent with pirenzepine (I) as an anti-ulcer agent in the test of indomethacine-induced gastric lesions in rats but was much weaker in tests for antocholinergic and antisecretory activity.

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