Koenigs-Knorr synthesis

From Fischer synthesis. b From Koenigs-Knorr synthesis. 

Koenigs-Knorr Synthesis / Reaction / Method / Glycosidation... 

In relation to carbohydrate chemistry, the Koenigs-Knorr synthesis of glycosides involves the treatment of glycosyl halides with an alcohol or phenol in the presence of a heavy metal salt.267 Karrer268 discovered that reaction of silver salts of hydros acids could also be used and use of these reagents has been extended more recently. Numerous variations and improvements on the original method have now been reported, and silver oxide, silver carbonate or silver trifluoromethanesulfonate have since become the accepted standard reagents.267... 

Because a substantial excess of the halide is used in the Koenigs-Knorr synthesis of cardenolides, it is usually difficult, if not impossible, to secure the acylated intermediate in crystalline form. Hence, Reichstein nd coworkers18 introduced a procedure whereby the whole of the products arising from the coupling reaction are saponified, employing a solution of potassium hydrogen carbonate in aqueous methanol. This modified transesterification procedure renders all extraneous carbohydrate materials water-soluble the methanol is removed by evaporation, leaving an aqueous solution from which the (deacylated) cardenolide may be obtained by... 

Koenigs-Knorr synthesis of aryl glucuronides. Steroid glucuronides of estrone, 17 /)-estradiol, estriol, and equilenin can be prepared in excellent yield by the reaction of the phenolic steroid with the bromo sugar (I) in toluene using cadmium carbonate as... 

Conrow, R B, Bernstein, S, Steroid Conjugates. VI. An improved Koenigs-Knorr synthesis of aryl glucuronides using cadmium carbonate, a new and effective catalyst, J. Org. Chem., 36, 863-870, 1971. 

Banoub, J., Bundle, D. R. 1,2-Orthoacetate intermediates in silver trifluoromethanesulfonate promoted Koenigs-Knorr synthesis of disaccharide glycosides. Can. J. Chem. 1979, 57, 2091-2097. 

Keto-5-phenyl-l-pentene, 572 Kharasch-Sosnovsky reaction, 66 Knoevenagel condensation, 342,507-508 Knorr pynole synthesis, 256-257 Koenigs-Knorr synthesis, 67... 

Koenigs-Knorr synthesis. The reaction of a poly-O-acylglycosyl halide with a hydroxylic component to form a glucopyranoside" is usually effected by use of silver oxide or silver carbonate. The much less expensive yellow mercuric oxide, together with a small amount of mercuric bromide, serves equally well and is not sensitive to light. The acid acceptor, by reaction with the hydrogen bromide formed, gives more catalyst. 

Koenigs-Knorr synthesis Mercuric oxide (p. 657). Nitromethane (p. 739). 

Koenigs-Knorr synthesis. Formation of glycosides from acetylated glycosyl halides and alcohols or phenols in the presence of silver carbonate or silver oxide. The reaction proceeds with inversion of configuration. 

Both the Koenigs-Knorr synthesis and catalytic oxidation may be utilized for the preparation of the steroid D-glucosiduronic acids. The first method is used if the steroid structure is altered by catalytic oxidation, for... 

Koenigs-Knorr synthesis. This catalyst system can be used in place of the usual silver oxide or silver carbonate in synthesis of alkyl -D-glucopyranosides, 3-D-galactopyranosides, and /3-D-xylopyranosides. The j3-anomers are formed almost exclusively in yields of 60-80%. The reaction is conducted in absolute chloroform in the presence of Drierite reactions are complete in 1-2 hr. at 25°. ... 

KOENIGS-KNORR REACTION Mercuric oxide-Mercuric bromide. Silver carbonate. KOENIGS-KNORR SYNTHESIS Silver carbonate-Celite. 

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