(3S)-3-[2-[3-(3-methoxypropylamino)-2-oxopyrazin-1-yl]butanoylamino]-4-oxo-5-(phenylmethylsulfanyl)pentanoic acid
(3S)-3-[2-[3-(3-methoxypropylamino)-2-oxo-pyrazin-1-yl]butanoylamino]-4-oxo-5-(phenylmethylsulfanyl)pentanoic acid
(3S)-3-[[2-[3-(3-methoxypropylamino)-2-oxo-1-pyrazinyl]-1-oxobutyl]amino]-4-oxo-5-(phenylmethylthio)pentanoic acid
(3S)-5-(benzylthio)-4-keto-3-[2-[2-keto-3-(3-methoxypropylamino)pyrazin-1-yl]butanoylamino]valeric acid