Koenigs-Knorr reaction synthesis

Koenigs-Knorr reaction (Section 25.6) A method for the synthesis of glycosides by reaction of an alcohol with a pyranosyl bromide. 

Koenigs-Knorr reaction of, 990 molecular model of, 119, 126, 985 mutarotation of, 985-986 pentnacetyl ester of, 988 pentamethyl ether of, 988 pyranose form of, 984-985 pyruvate from. 1143-1150 reaction with acetic anhydride, 988 reaction with ATP, 1129 reaction with iodomethane, 988 sweetness of. 1005 Williamson ether synthesis with. 988... 

A number of glycosides were available to Fischer by way of the Koenigs-Knorr reaction and his own glycoside synthesis, which involves treatment of... 

Most of the methods available for the synthesis of this class of compoimd have been referred to in the preceeding pages. These include the modified Koenigs-Knorr reaction (p. 406), the use of glycosyl halides with non-... 

M. Dejter-Juszinsky and H. M. Flowers, Koenigs-Knorr reaction. 11—synthesis of an oi-L-linked disaccharide from tri-O-benzyl-L-fucopyranosyl bromide, Carbohydr. Res. 18 219 (1971). 

An aglyconic derivative of KDO, having 0-7 and 0-8 temporarily blocked, was required for the synthesis of the model disaccharide Koenigs-Knorr reaction of 3 with a suitable halide derivative of KDO would be expected to occur exclusively at the (equatorial) 0-4 while 0H-5, being axially-disposed and experiencing additional steric shielding by H-7, would be practically unreactive. X-ray crystal structure analysis of KDO derivatives (14, 15) has shown that H-7 is orient-... 

Despite its wide application in glycoside synthesis, the Koenigs-Knorr reaction suffers from several disadvantages (i) the glycosyl halides are unstable, (ii) excess toxic heavy metals are needed to activate the donor, and (iii) a desiccant (to absorb any liberated water) and an acid acceptor (to absorb the liberated hydrogen halide and can be a promoter itself) are often needed to increase the yield and suppress side reactions. 

Helferich, Bohm and Winkler1 have reported that the use of iodine catalyzed the Koenigs-Knorr reaction, which was exceedingly slow when calcium chloride was used as an internal desiccant. This catalyst has since been used by a number of other workers.79 111-114 The work of Talley, Reynolds and Evans79 on the synthesis of the orthoester type of oligosaccharides, indicated that the presence of iodine favored the formation of a normal biosidic linkage, whereas the absence of iodine favored the formation of an orthoester linkage. 

A substantial improvement in the synthesis of steroid /3-D-glucosid-uronic acid derivatives was achieved by Conrow and Bernstein,125 who introduced cadmium carbonate as a new and effective catalyst in the Koenigs-Knorr reaction procedure its use proved to be particularly convenient in the synthesis of such derivatives of phenolic steroids, where the yields obtained by using silver carbonate had not usually exceeded 10%. Thus, by employing cadmium carbonate, several succesful syntheses in the series of phenolic steroids have been claimed (see, for example, Ref. 126). 

D-galactopyranosyl-D-mannose (epilactose) (15). This was the culmination of a lifetime s research on lactose by C. S. Hudson. The essential step in their synthesis (see Fig. 2) was the Koenigs-Knorr reaction of... 

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