THE BROMINOLYSIS OF CARBOHYDRATE IODIDES: II. A SYNTHETIC ROUTE TO 2,5-ANHYDROSUGARS

1964 ◽  
Vol 42 (3) ◽  
pp. 547-549 ◽  
Author(s):  
R. U. Lemieux ◽  
B. Fraser-Reid
Keyword(s):  
Acetic Acid ◽  
Hydrogen Chloride ◽  
Potassium Acetate ◽  
Quantitative Yield ◽  
Equimolar Mixture ◽  
Silver Acetate ◽  
Synthetic Route ◽  
Fold Excess

Reaction of methyl 2-deoxy-2-iodo-β-D-glucopyranoside triacetate with a 20-fold excess of bromine and a 10-fold excess of silver acetate in a 10% solution of potassium acetate in acetic acid gave a near-quantitative yield of an equimolar mixture of the anomeric forms of 1,3,4,6-tetra-O-acetyl-2,5-anhydro-1-methoxy-D-mannose. Treatment of the mixture with methanolic hydrogen chloride gave the dimethylacetal of 2,5-anhydro-D-mannose (chitose).

THE BROMINOLYSIS OF CARBOHYDRATE IODIDES: I. ACETYLATED 6-DEOXY-6-IODO AND 2-DEOXY-2-IODO GLYCOSIDES

1964 ◽  
Vol 42 (3) ◽  
pp. 539-546 ◽  
Author(s):  
R. U. Lemieux ◽  
B. Fraser-Reid
Keyword(s):  
Acetic Acid ◽  
Methoxy Group ◽  
Glacial Acetic Acid ◽  
Main Product ◽  
Zinc Dust ◽  
Potassium Acetate ◽  
Borohydride Reduction ◽  
Silver Acetate ◽  
Sodium Borohydride Reduction ◽  
Dust Reduction

Reaction of methyl 6-deoxy-6-iodo-α-D-glucopyranoside triacetate with an excess of bromine in glacial acetic acid; N in potassium acetate, gave a 1.1:1 mixture of the products resulting from replacement of the iodine by bromine and by acetoxy group, respectively. When 2 moles of silver acetate were present per mole of bromine, the reaction was much more rapid and only methyl α-D-glucopyranoside tetraacetate was formed. The brominolysis of methyl 2-deoxy-2-iodo-α-D-mannopyranoside triacetate proceeded at a useful rate only when catalyzed by silver acetate. The main product of the reaction appeared to be methyl 3-acetoxy-2-bromo-2-deoxy-α-D-arabino-hexopyranoside triacetate. The compound could be converted by way of sodium borohydride reduction to methyl 2-bromo-2-deoxy-α-D-altropyranoside and by way of zinc dust reduction to methyl 2-deoxy-α-D-erythro-hexopyranoside-3-ulose diacetate. About 20% of the reaction proceeded with migration of the methoxy group to the 2-position to yield 2-O-methyl-D-glucose tetraacetate. The mechanisms of these reactions are discussed.

REACTIONS OF 2-ACETOXY-4,6-DI-O-ACETYL-3-O-(2,6-DICHLOROBENZOYL)-D-GLUCAL, TRI-O-ACETYL-3-DEOXY-α-D-erythro-HEX-2-ENOPYRANOSYL CHLORIDE, AND RELATED COMPOUNDS

1966 ◽  
Vol 44 (15) ◽  
pp. 1855-1862 ◽  
Author(s):  
R. U. Lemieux ◽  
R. J. Bose
Keyword(s):  
Acetic Acid ◽  
Sulfuric Acid ◽  
Acetic Anhydride ◽  
Potassium Acetate ◽  
Equimolar Mixture ◽  
Related Compounds ◽  
Reaction Compound

Attempts to dehydrobrominate tri-O-acetyl-3-O-tosyl-α-D-glucopyranosyl bromide with diethylamine led directly to products resulting from the replacement of the tosyloxy group by the diethylamine. It was readily possible to prepare 2-acetoxy-di-O-acetyl-3-(2,6-dichlorobenzoyl)-D-glucal (V). Acetolysis of this compound gave an equimolar mixture of the α- and β-anomers (II and VI, respectively) of 2-acetoxy-di-O-acetyl-pseudo-D-glucal as the first products of the reaction. Compound V reacted only reluctantly with methanol in pyridine to give a mixture of the anomeric methyl di-O-acetyl-3-deoxy-D-erythro-hex-2-enopyranosides. These glycosides were readily prepared by reaction of tri-O-acetyl-3-deoxy-α-D-erythro-hex-2-eno-pyranosyl chloride with methanol in the presence of pyridine. 2-Acetoxy-di-O-acetyl-3-O-mesitoyl-D-glucal was prepared from 3-O-mesitoyl-β-D-glucose. The anomerizations of compounds II and VI were examined with both sulfuric acid in 1:1 acetic acid – acetic anhydride and potassium acetate in acetic acid. The conformations of II and VI are discussed, as are a number of the mechanistic features of the reactions studied.

Electron Microprobe Analyses of the Remineralization of Enamel

1970 ◽  
Vol 49 (3) ◽  
pp. 621-625 ◽  
Author(s):  
Stephen H.Y. Wei
Keyword(s):  
Acetic Acid ◽  
Electron Microprobe ◽  
Potassium Acetate ◽  
Enamel Surface ◽  
Acetate Buffer ◽  
Demineralized Enamel ◽  
Calcium And Phosphorus

The electron microprobe was used to analyze the calcium and phosphorus concentrations of sound, acid-etched, and remineralized enamel. By use of a weak acetic acid-potassium acetate buffer, it was found that the demineralization probably affected only the first 10 micrometers of the enamel surface. This demineralized enamel was successfully remineralized by the use of a calcifying solution. The changes in calcium and phosphorus concentrations and the Ca/P ratios were determined.

Stereoselective deprotonation of tropinone and reactions of tropinone lithium enolate

1992 ◽  
Vol 70 (10) ◽  
pp. 2618-2626 ◽  
Author(s):  
Marek Majewski ◽  
Guo-Zhu Zheng
Keyword(s):  
Acetic Acid ◽  
Ring Opening ◽  
Aldol Reaction ◽  
Ethyl Chloroformate ◽  
Lithium Diisopropylamide ◽  
Silver Acetate ◽  
Lithium Amides ◽  
Lithium Enolate ◽  
The Absolute ◽  
Absolute Stereochemistry

Tropinone (6) was deprotonated with lithium diisopropylamide and with chiral lithium amides (18–24) and the resulting enolates (two enantiomers) were treated with electrophiles. The aldol reaction with benzaldehyde and deuteration were both diastereoselective. The former yielded only one isomer (exo, anti) of the aldol 8a; the latter proceeded from the exo face. This selectivity permitted us to probe the deprotonation of tropinone with lithium amides; it was concluded that the reaction involves predominantly the exo axial protons. The reaction of tropinone enolate with ethyl chloroformate led, via a ring opening, to the cycloheptenone derivative 9. The reaction with methyl cyanoformate yielded, in the presence of silver acetate and acetic acid, the β-ketoester 8b; however, in the absence of these additives, and especially when 12-crown-4 was added to the enolate, a ring opening leading to the pyrrolidine derivative 10 occurred instead. Deprotonation of tropinone with chiral lithium amides proceeded with modest enantioselectivity. A synthesis of non-racemic anhydroecgonine via this strategy allowed establishing the absolute stereochemistry of deprotonation.

Improved synthesis of anti-sesquinorbornene

1984 ◽  
Vol 62 (9) ◽  
pp. 1840-1844 ◽  
Author(s):  
Karl R. Kopecky ◽  
Alan J. Miller
Keyword(s):  
Acetic Acid ◽  
Sulfuric Acid ◽  
Carboxylic Acid ◽  
Lead Tetraacetate ◽  
Carboxyl Group ◽  
Silver Acetate ◽  
Benzenesulfonyl Chloride ◽  
Methoxide Ion ◽  
Hydrolysis Of ◽  
Monomethyl Ester

Treatment of methyl hydrogen decahydro-1,4:5,8-exo,endo-dimethanonaphthalene-4a,8a-dicarboxylate with lead tetraacetate in benzene – acetic acid replaces the carboxyl group by an acetoxy group. Hydrolysis of this product with 25% sulfuric acid at 130 °C forms 8a-hydroxydecahydro-1,4:5,8-exo,endo-dimethanonaphthalene-4a-carboxylic acid 10. The reaction between 10 and benzenesulfonyl chloride in pyridine containing triethylamine at 95 °C produces anti-sesquinorbornene 1 in 34% yield. In the absence of triethylamine 1 is converted to the hydrochloride. The iodohydroperoxide of 1 is converted by silver acetate at 0 °C to the diketone in a luminescent reaction. The 1,2-dioxetane could not be isolated. Decahydro-1,4:5,8-exo,exo-dimethanonaphthalene-4a,8a-dicarboxylic anhydride is converted slowly by methoxide ion in methanol at 150 °C to the monomethyl ester which then undergoes demethylation. The isomeric exo,endo anhydride undergoes reaction readily with methoxide ion at 80 °C.

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.

The Activity Coefficients of the Undissociated Part of Weak Acids. I. Acetic Acid in Potassium Acetate Solutions

1939 ◽  
Vol 61 (1) ◽  
pp. 65-67 ◽  
Author(s):  
W. D. Larson ◽  
W. J. Tomsicek
Keyword(s):  
Acetic Acid ◽  
Activity Coefficients ◽  
Potassium Acetate ◽  
Weak Acids
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