Ergothioneine in a peptide: Substitution of histidine with 2‐thiohistidine in bioactive peptides

Ergothioneine (EGT) is the betaine of 2‐thiohistidine (2‐thioHis) and may be the last undiscovered vitamin. EGT cannot be incorporated into a peptide because the α‐nitrogen is trimethylated, although this would be advantageous as an EGT‐like moiety in a peptide would impart unique antioxidant and metal chelation properties. The amino acid 2‐thioHis is an analogue of EGT and can be incorporated into a peptide, although there is only one reported...