Synthesis of Glycosides from Glycosyl Halides

0-Glycosides Hemiacetals 1,2-Anhydro derivatives Phosphites, phosphates Orthoesters Carbonates Others 

Originally used in catalytic amounts in combination with silver oxide and silver carbonate in Koenigs-Knorr reactions, iodine was shown to promote glycosylations either alone or in combination with DDQ [74]. Iodine bromide was reported to be a more efficient promoter [75]. 

For the glycosylation of phenols with glycosyl halides, phase-transfer conditions using aqueous sodium or potassium hydroxide and quaternary ammonium salts have also been reported [89-94]. By using phase-transfer catalysis, a method for solid-phase synthesis of aryl glycosides was developed [95]. 

Moreover, electrochemical [96], thermal [97-100] and high-pressure glycosylations 

Glycosyl fluorides are too unreactive to be activated under standard Koenigs-Knorr conditions, and, for this reason, their use as glycosyl donors was explored relatively late, after the development of glycosyl bromides. They were introduced in 1981 [103], and glycosyl fluorides are currently among the most frequently used donors. 

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Koenigs-Knorr glycosidation Synthesis of alkyl or aryl O-glycosides from glycosyl halides and alcohols or phenols, respectively. 246... 

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. 

The first synthesis of methyl 4-thiomaltoside (36b) (34%), 4-thiocellobioside (39d) (52%) and 4-thiodigalactobioside (86) (56%) was reported 18 years ago by using the Sn2 displacement of 1,2-cis- or 1,2-trans- glycosyl halides (9 a), (7 a) and (7c) with methyl 4-thio-a-D-glycopyranoside sodium salts generated from the acetylated methyl glycosides (84) and (85a) (Scheme 25) [14a]. 

Benzyl glycosides may be prepared by the Koeiiigs-Knorr glycoside synthesis from benzyl alcohol plus a glycosyl halide, or from benzyl alcohol and the sugar in the presence of an acid. ... 

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