L-Phototryptophan

Phototryptophan is a new photoactivatable amino acid designed to be incorporated into tryptophan-containing peptides for photoaffinity labeling. The synthesis of phototryptophan starts from 6-bromoindole with the installation of an 1-azi-2,2,2-trifluoroethyl moiety, followed by microwave-assisted condensation with serine under mild conditions. Separation of the N-acetylated enantiomers was possible by employing Aspergillus aminoacylase. Differential scanning calorimetry showed that phototryptophan is thermally stable up to 100 degrees C. Boc-L-Phototryptophan was used to assemble a diazirine analog of the marine natural product hemiasterlin.