A new tool for photoaffinity labeling studies: a partially constrained, benzophenone based, alpha-amino acid

The novel alpha-amino acid BpAib, a partially conformationally restricted analogue of the currently extensively used 3-(4-benzoylphenyl)alanine (Bpa) photoaffinity label, was synthesized, optically resolved, fully characterized, and appropriately derivatized. An intermolecular photocrosslinking experiment highlighted its regioselective reactivity towards the S-methyl side-chain group of a Met-based dipeptide, which is closely comparable to that of Bpa.