Synthesis of Glycopyranosides

In 1879, Michael14 reported that phenyl /3-D-glucopyranoside (3) is obtained by the reaction of tetra-O-acetyl-a-D-glucopyranosyl chloride (1) with potassium phenoxide in aqueous solution. Under the reaction 

Although silver carbonate or silver oxide is usually used as the acid acceptor in the Koenigs-Knorr reaction, numerous variations and improvements have been reported. Zemplen and coworkers19-21 used mercury(II) acetate instead of a silver salt. Helferich and coworkers22-24 used mercury(II) cyanide and mercury(II) bromide. Wulff and Rdhle1 f used the silver salts of a number of organic acids. 

The procedure developed by Meystre and Miescher,30 in which the water formed is removed as its azeotrope with benzene, has been used extensively (see, for examples, Refs. 31 and 32). The yields of the aforementioned glycosidation reactions are moderate to good with primary alcohols, but are often rather poor with secondary alcohols, particu- 

Reactions37 of Tigogenin (12) with Tetra-O-acetyl-a-D-glucopyranosyl Bromide (2) in Ether in the Presence of Silver Salts at 20° 

Bredereck and coworkers43 44 prepared /3-D-glucosides by using O-tritylated sugars. Thus, the reaction of l,2,3,4-tetra-0-acetyl-6-0-trityl-/3-D-glucopyranose (15) with tetra-O-acetyl-a-D-glueopyranosyl 

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A novel approach to the synthesis of glycopyranosides has involved the pyrolysis of acylated glycopyranosyl carbonates. Pyrolysis of (27 R = Me or Ph,... 

U. Aich and D. Loganathan, Zeolite-catalyzed Helferich-type glycosylation of long-chain alcohols. Synthesis of acetylated alkyl 1, 2-trans glycopyranosides and alkyl 1, 2-cis C2-hydroxy-glycopyranosides, Carbohydr. Res., 342 (2007) 704-709. 

A. K. Misra, P. Tiwari, and G. Agnihotri, Ferrier rearrangement catalyzed by HC104-Si02 Synthesis of 2,3-unsaturated glycopyranosides, Synthesis, 2 (2005) 260-266. 

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]. 

B. Fraser-Reid and B. J. Carthy, Synthesis of some a-cyclopropylcarbonyl glycopyranosides, Can. J. Chem. 50 2928 (1972). 

Sakurai et al. as well as Sandhoff et al. used this approach for the synthesis of allyl-C-glycopyranosides 21 from readily accessible peracetylated or perbenzylated glycopyranoses 19 [12, 13]. Addition of allylsilane to oxonium 20 proceeds with an axial/equatorial selectivity that is considerably affected by the polarity of the solvent (Scheme 13.9). 

Synthesis of Alkyl 2-Deoxy-a-D-glycopyranosides and Their 2-Deuterio Derivatives, R. U. Lemieux and S. Levine, Can. J. Chem., 42 (1964) 1473-1480. 

C. Leteux and A. Veyrieres, Synthesis of a-C-glycopyranosides of D-galactosamine and D-glucosamine via iodocyclization of corresponding glycals and silver tetrafluoroboranuide-promoted alkynylation at the anomeric center, J. Chem. Soc., Perkin Trans. 1, (1994) 2647-2655. 

Schmidt and Wernicke74 have described a synthesis of digitalose starting with D-fucose dibenzyl mercaptal, which on condensation with acetone yielded the 4,5-isopropylidene derivative (LXXIV). Elimination of the dibenzyl mercaptal residues with mercuric chloride and cadmium carbonate in methanol gave 4,5-isopropylidene-D-fucose dimethylacetal (LXXV), from which the 2-benzyl ether was obtained on treatment with sodium and benzyl chloride. Methylation produced 2-benzyl-3-methyl-4,5-iso-propylidene-D-fucose dimethyl acetal (LXXVI), from which the iso-propylidene group was eliminated on treatment with methanolic hydrogen chloride, which also effected glycopyranoside formation (LXXVII). The... 

Fig. 8 Different products with sucrose analogues as substrates [91]. Enzymatic synthesis of levans headed with different glycopyranosides by levansucrases of different sources. 6-kestose by a Ls variant N252A, and 1-kestose, 1-nystose analogues by P-fructofuranosidase of A. niger...

It seems probable that a fundamental distinction may exist between the two methods available for the synthesis of carbohydrate boronates, in that, under dehydration conditions, esterifications may be reversible, whereas boronate formation from borinates is not. In the first, therefore, products may be thermodynamically controlled, whereas kinetic control will operate in the second. It is noteworthy, however, that products obtained from several glycopyranosides (a) by use of an ethylboronate derivative, and (b) by way of the per(diethylbor-inates) had the same structures.338... 

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