Incorporation of labile trans-4,5-difluoromethanoproline into a peptide as a stable label for 19F NMR structure analysis

- Intrinsically unstable amino acid was incorporated into a cyclic peptide (gramicidin S).
- Difluorocyclopropanation was done on the stable dipeptide building block.
- The amino acid did not perturb the conformation and function of gramicidin S.
- The peptide was evaluated in solid state 19F NMR structure analysis.
- Geminal-F2 system delivers several orientational constrain at one spectrum.