Konigs-Knorr reaction

This ether, developed for the protection of a pyranoside anomeric hydroxyl, is prepared via a Konigs-Knorr reaction from the glycosyl bromide and 2-(ben-zylthio)ethanol in the presence of DIPEA. It is cleaved, after oxidation with dimethyldioxirane, by treatment with LDA or MeONa. ... 

Ketosis, relation to carbohydrate oxidation, II, 145-159 theory of, II, 146 a-Ketovaleric acids, V, 50 Konigs-Knorr reaction, I, 79, 114 a-glycoside formation in, I, 84 Kojic acid, III, 373 from sucrose, IV, 322, 324... 

On deacetylation of the latter compound by the method of Zempl n and Pacsu, a water-soluble, non-reducing, crystalline mass with [a]D — 12.7° in aqueous solution, was obtained. Although it could not be recrystallized from any solvent, the substance gave the correct analysis for a methyl fructoside monoacetate. Hydrolysis with alkali did not liberate the acetyl group. Crystalline acetylfructosyl bromide gave essentially the same results in the Konigs-Knorr reaction as were obtained with the chloro-compound. 

Miss Frush and IsbelF applied the Konigs-Knorr reaction to their crystalline pentaacetyl-a-D-(a)-guloheptosyl bromide and succeeded in isolating the tetraacetyl-D-(a)-guloheptose methyl 1,2-orthoacetate (XIII) in nearly quantitative yield. The operation was carried out by shaking a mixture of powdered Drierite (anhydrous calcium sulfate), freshly prepared silver carbonate and the crystalline bromide in methanol at 0° for forty-four hours. The reaction was studied by analysis of the final solution. The difference between the results obtained by acid (0.1 N) and by alkaline (0.1 N) hydrolysis determined the amount of orthoacetate. Within experimental error the reaction product consisted exclusively of the orthoacetate. 

Miss Frush and IsbelF used crystalline heptaacetyl-a-neolactosyl chloride in the Konigs-Knorr reaction under conditions identical with those described for pentaacetyl-a-D-(a)-guloheptosyl bromide, with the exception that the reaction time was increased to seventy-two hours. Acid and alkaline hydrolysis of the reaction solution showed that only about 70% of the original sugar was present, and that this was almost completely in the form of the orthoester. By extraction of the silver residues with chloroform, a halogen-free sirup was obtained, from which short rectangular crystals separated upon addition of methyl alcohol. This substance was methyl /3-neolactoside heptaacetate, which exhibited the expected normal behavior. 

The normal Konigs-Knorr reaction is a Svl type reaction with complete inversion on carbon atom 1 ... 

Levene and Tipson studied the behavior of acetyl-n-ribosyl bromide in the Konigs-Knorr reaction. The reaction of methanol upon acetyl-D-ribosyl bromide in the presence of freshly prepared silver carbonate took place at room temperature in thirty minutes. The crystalline bromo-... 

The synthesis of the disaccharide dipeptide (76), an analogue of (75), has been described recently (20). The tetra-O-benzoyl-a-D-glucopyranosyl bromide was condensed by a Konigs-Knorr reaction with benzyl-2-acet-amido-6-0-benzoyl-3-0-(D-l-carboxyethyl)-2-deoxy-a-D-glucopyrano-... 

Silver carbonate (s. a. under AgClOJ Acylglycosides from acylbromosugars Konigs-Knorr reaction... 

Silver perchlorate silver carbonate Modified Konigs-Knorr reaction Disaccharides... 

---