Synonyms: (4S)-4-(2-methylpropyl)-2-Pyrrolidinone, 2-Pyrrolidinone, 4-(2-methylpropyl)-, (S)-, (S)-4-(Isobutyl)pyrrolidin-2-one, Pregabalin EP impurity A, (S)-Pregabalin lactam, (4S)-4-(2-methylpropyl)-2-Pyrrolidinone, 2-Pyrrolidinone, 4-(2-methylpropyl)-, (S)-, (S)-4-(Isobutyl)pyrrolidin-2-one