Stereoselective glycosylations using group

H. Tokimoto, Y. Fujimoto, K. Fukase, and S. Kusumoto, Stereoselective glycosylation using the long-range effect of a [2-(4-phenylbenzyl)oxycaibonyl]benzoyl group, Tet. Asymm., 16 (2005) 44 1 4-i7. 

This strategy appears to be very attractive because of the possibility of completely solubilizing the support in most of the common solvents. From a chemical perspective, that property allows one to benefit from all the solvent conditions used in classical solution chemistry. This could prove to be very advantageous, especially to obtain stereoselective glycosylation without neighboring-group assistance. Moreover, isolation and purification of the polymer is easily achieved by precipitation usually in diethyl ether or methyl-tert-butyl ether (MTBE) and recrystallisation from ethanol. One major drawback of this type of support is its tendency to solidify at low temperature, thus limiting the variety of temperature conditions. 

The Fmoc group, which is very useful in peptide synthesis [32], has proved an efficient tool in glycopeptide chemistry [10], Because the Fmoc protection of the amino function is rather stable to acids, it can be combined with fert-butyl-type protecting groups and exposed to stereoselective glycosylations that require a more or less acidic milieu. 

Ito, Y, Ogawa, T, An efficient approach to stereoselective glycosylation of A-acetylneuraminic acid use of phenylselenyl group as a stereocontrolling auxiliary. Tetrahedron Lett., 28, 6221-6224, 1987. Lemieux, R U, Hendriks, K B, Stick, R V, James, K, Halide ion catalyzed glycosidation reactions. Syntheses of a-linked disaccharides, J. Am. Chem. Soc., 97, 4056-4062, 1975. 

Egusa, K, Fukase, K, Nakai, Y, Kusumoto, S, Stereoselective glycosylation and oligosaccharide synthesis on solid support using a 4-azido-3-chlorobenzyl group for temporary protection, Synlett, 27-32, 2000. 

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