Protecting groups, glycopeptide synthesis

Sjolin, P, Kihlherg, J, Use of fluorobenzoyl protective groups in synthesis of glycopeptides (1-ehmination of O-hnked carbohydrates is suppressed, J. Org. Chem., 66, 2957-2965, 2001. 

To overcome these difficulties in the selective deprotection and chain extension, several carboxyl-protecting groups, namely, allyl (16,32), benzyl (43,44), tert-butyl (42), 2-bromoethyl (45), 2-chloroethyl (45), heptyl (46), 4-nitrophenyl (47,48), and pentafluorophenyl (49) for L-serine/L-threonine have been introduced or applied. Similarly, amino-protecting groups for L-serine/L-threonine that have proved useful for the synthesis of glycopeptides are tm-butyloxycarbonyl (50), 9-fluorenylmethoxycarbonyl (43,44,48), 2-(2-pyridyl)ethoxycarbonyl (51), 2-(4-pyridyl)ethoxycarbonyl (44,52), and 2-triphenylphosphonioethoxycarbonyl (53). Some applications of these groups have been discussed in earlier reviews (7-11). 

Besides acetyl, benzoyl, and benzyl protecting groups for the carbohydrate hydroxyl groups, silyl, isopropylidene, and p-methoxybcnzyl groups have also been employed in solid-phase glycopeptide synthesis. The synthesis of a glycopeptide... 

M Meldal, KJ Jense. Pentafluorophenyl esters for temporary protection of the a-carboxy group in solid phase glycopeptide synthesis. J Chem Soc Chem Commun 483, 1990. 

Scheme 2 O- and /V-S ugar Protecting Groups Used in Glycopeptide Synthesis...

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. 

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