Aromatic capping surprisingly stabilizes furan moieties in peptides against acidic degradation

We herein describe the synthesis of furan containing peptides for further post-synthetic derivatisation in solution through our recently developed furan-oxidation-labeling technology. Previously, it was reported by others that during acidic cleavage of furan-modified peptides, furan moieties can suffer from degradation. We demonstrate here that this degradation is position dependent and can be fully suppressed through introduction of proximate aromatic residues. Versatile introduction of 2-furylalanine at internal, C-terminal as well as the sensitive N-terminal positions has now been proven possible.