General strategy for the preparation of membrane permeable fluorogenic peptide ester conjugates for in vivo studies of ester prodrug stability.

To study ester prodrug stability properties in living cells we have conjugated fluorogenic esters to the cell membrane permeable peptide Arg9. The desired conjugates are prepared by coupling N-maleoyl amino acid esters of monoalkylated fluoresceins or fluorescein to TyrArg9Cys. The photophysical properties of the monoalkylated fluorescein derivatives are described.