3-(2-carboxy-ethyl)-5-oxo-4,5,6,7-tetrahydro-1H-pyrrolo[2,3-c]pyridine-2-carboxylic acid

5-aminomethyl-3-(2-carboxy-ethyl)-4-carboxymethyl-pyrrole-2-carboxylic acid

3-(2-carboxy-ethyl)-4-carboxymethyl-5-(hydroxyimino-methyl)-pyrrole-2-carboxylic acid

3-(2-ethoxycarbonyl-ethyl)-5-oxo-4,5,6,7-tetrahydro-1H-pyrrolo[2,3-c]pyridine-2-carboxylic acid ethyl ester

5-aminomethyl-3-(2-ethoxycarbonyl-ethyl)-4-ethoxycarbonylmethyl-pyrrole-2-carboxylic acid ethyl ester