(2S)-1-[(2S,4S)-4-(pyrrolidine-1-carbonyl)pyrrolidine-2-carbonyl]pyrrolidine-2-carbonitrile
(2S)-1-[oxo-[(2S,4S)-4-(oxo-1-pyrrolidinylmethyl)-2-pyrrolidinyl]methyl]-2-pyrrolidinecarbonitrile
(2S)-1-[(2S,4S)-4-pyrrolidin-1-ylcarbonylpyrrolidin-2-yl]carbonylpyrrolidine-2-carbonitrile