Analytical methods protected peptides

Yet we have to differentiate between the two tasks to determine a maximal amount of amino functions on polymer to monitor the total capacity of the support, e.g., after deprotection/deprotonation on one side, and on the other to detect only traces of amino groups remaining eventually after the peptide coupling reaction. In the first case the analytical methods employed are not limited by the presence of labile N-tenninal protecting groups as in controlling the completion of the peptide synthesis step. 

Difficulties encountered in the postsynthetic chemical sulfation of peptides and the correspondingly low yields have led to the proposal of an alternative approach. This approach makes use of appropriate tyrosine 0-sulfate derivatives for the chain elongation steps in solution and on solid supports by applying protection strategies compatible with the acid sensitivity of the sulfate ester. Moreover, the analytical characterization of the peptides synthesized with tyrosine 0-sulfate derivatives is greatly facilitated since contaminations deriving from the preparation of the intermediates are easily detected by chromatographic (HPLC and CE) and spectroscopic methods (see Table 2). 

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