Glycopeptides protecting groups

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). 

Selective methods for deprotecting glycopeptides either at the amino or at the carboxyl terminus have been developed during the past decade by introduction and application of different combinations of protecting groups (Table II). 

Different Amino and Carboxyl Protecting-Group Combinations of L-Serine/L-Threonine Used for Glycopeptide Chain-Lengthening... 

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... 

The detachment of the glycopeptide from the resin and deprotection of the amino acid side chains as well as the removal of the acid-labile carbohydrate protecting groups were simultaneously carried out using TFA/H20/thioanisole/ethanedithiol (87.5 5 5 2.5). This treatment proceeded without affecting the glycosidic bonds and furnished the target molecule 38. 

Strategy 1 Chemical (R = protecting group) or enzymatic glycosylation (R = H) of peptide or glycopeptide ... 

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

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