That's already been done many times over. Out of hundreds executed, There are a handful of interesting ones, benzoylphenylalanine, azidophenylalanine, phenylalanine methyl ketone, and bipyalanine, but the thing is, that nature really has a good selection of amino acids to accomplish just about anything it could do. The reliable chemistries that are compatible with a water solvent are few, which is why so much organic chemistry is done in nonaqueous solvent.