Therefore, the preparation of synthetic phosphorylated peptides is of significant interest for researchers. However, those synthetic efforts are frequently hampered by the lability of the phosphoester bond.

Here we present three phosphono-amino acid derivatives that serve as hydrolysis-stable mimics of pSer, pThr and pTyr, termed Pma (Ser), Pmab (Thr) and Pmp (Tyr). Those derivatives are suitably protected for their use in peptide synthesis using the Fmoc strategy. The tert-butyl protecting groups on the phosphonic acid moieties prevent side reactions by this group and can be removed during final deprotection of the peptide.

Phosphoserine, -threonine and -tyrosine (left), and their phosphono-analogs Pma, Pmab and Pmp (right).

The stability towards hydrolysis that characterizes the phosphono-derivatives has an additional benefit, which is that cellular phosphatases are unable to remove the phosphate group mimic. Consequently, peptides or semi-synthetic proteins that include Pma, Pmab or Pmp are valuable tools for cell-based experiments.

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