Synthesis of a phosphotyrosine analog, BrPmp and its incorporation into peptides

Protein tyrosine phosphatases (PTPs) are important therapeutic targets for medicinal chemists and biochemists. General strategies for the development of inhibitors of these enzymes are needed. One known inhibitor of PTPs are analogs containing the α-bromobenzylphosphonate (BBP) motif. We hypothesized that the BBP functional group could be used to develop targeted PTP inhibitors, by incorporation into peptide sequences. Using model compounds, we first tested the stability of the BBP motif to solid phase peptide synthesis (SPPS) conditions. A scaleable synthetic methodology was then developed for generating an amino acid analog that incorporates the BBP functional group. Enzyme inhibition studies with the PTP CD45 demonstrated that the BBP amino acid derivatives were irreversible inhibitors. Using the Fmoc protected BrPmp BBP amino acid, we then incorporated it into longer peptide sequences. We were able to generate a short series of nonapeptides that incorporated BrPmp and identify areas of the chemistry which required improvement.