(R)-alpha-Trifluoromethylalanine as a F-19 NMR Probe for the Monitoring of Protease Digestion of Peptides

Fluorinated non-natural amino acids are useful tools for improving the bioavailability of peptides but can also serve as fluorinated probes in F-19 NMR-based enzymatic assays. We report herein that the use of the non-natural alpha-quaternarized (R)-alpha-trifluoromethylalanine ((R)-alpha-TfmAla) provides convenient and accurate monitoring of trypsin proteolytic activity and increases resistance towards pepsin degradation.