2-[cyclopentyl-(3-methyl-2-sulfanylbenzoyl)amino]acetic acid 2-[cyclopentyl-(3-methyl-2-sulfanyl-benzoyl)amino]acetic acid 2-[cyclopentyl-[(2-mercapto-3-methylphenyl)-oxomethyl]amino]acetic acid 2-[cyclopentyl-(2-mercapto-3-methyl-benzoyl)amino]acetic acid 2-[cyclopentyl-(3-methyl-2-sulfanyl-phenyl)carbonyl-amino]ethanoic acid