4-(2,5-dimethylpyrrol-1-yl)butanoic acid

4-[(2-chloroacetyl)amino]butanoic acid

4-(4-氯苄氨基)丁酸

4-[[(3-nitro-6-oxocyclohexa-2,4-dien-1-ylidene)-phenylmethyl]amino]butanoic acid

4-[(4-甲氧基苯甲酰基)氨基]丁酸