<jats:title>Abstract</jats:title> <jats:p>A new amino acid, galantinic acid, was found as one of the constituent amino acids in a peptide antibiotic galantin I. The structure of galantinic acid was determined to be (2S,4S,5S)-5-amino-2-carboxymethyl-4-hydroxytetrahydropyran on the basis of NMR and CD studies.