Wiktionary
dehydroalanine
n. An uncommon amino acid found in peptides of microbial origin.
Wikipedia
Dehydroalanine
Dehydroalanine (Cα,β-didehydroalanine, (alpha)-(beta)-di-dehydroalanine, or 2,3-didehydroalanine) is a dehydroamino acid. It is an α-amino acid found as a residue in peptides of microbial origin. It is unusual in having an unsaturated backbone.