Solid-phase glycosylation of peptide templates and on-bead MAS-NMR analysis: Perspectives for glycopeptide libraries

The efficient solid-phase glycosylation of amino acid side chains (serine ( Ser), threonine (Thr), and tyrosine (Tyr)) in peptides was demonstrated wit h a variety of glycosyl trichloroacetimidate donors in high yields and puri ties. A novel photolabile linker, with no chiral centre, was introduced to facilitate analysis by both matrix-assisted laser desorption ionisation tim e of flight (MALDI-TOF) mass spectrometry and nanoprobe magic angle spinnin g (MAS) NMR spectroscopy. Product analysis by nanoprobe MAS NMR spectroscop y, LC-MS and MALDI-TOF mass spectrometry of the glycosylation reactions ind icated that the reactivity order of the hydroxy side-chain functions of ami no acids in peptides on the solid-phase was Tyr > Ser > Thr. The nearly qua ntitative glycosylation yields and the efficient on-bead product analysis b y nanoprobe MAS NMR spectroscopy have made a truly solid-phase approach for the synthesis and analysis of glycopeptide libraries possible.