Acid hydrolysis of ristocein A yields a number of amino acids of unusual structure. One set of diastereoisomeric pairs has a molecular weight of 362 and an empirical formula of C 17 H 18 N 2 O 7 . Mass spectral and nuclear magnetic resonance (NMR) evidence suggest a diphenyl ether with hydroxyl and α-amino acid [-CH-(NH 2 )COOH] groups on one ring, and methyl, hydroxyl and α-amino acid groups on the other ring. Coupling in the NMR and nuclear Overhauser effect experiments favor certain substitution patterns, which are shown. Another set of diastereoisomers seems to be a lower homolog of the previous set, without the aromatic methyl group.