N-[(2S)-1-(3-methylbutylamino)-1-oxo-3-phenylpropan-2-yl]pyrazine-2-carboxamide; (S)-N-(1-(Isopentylamino)-1-oxo-3-phenylpropan-2-yl)pyrazine-2-carboxamide; N-[(1S)-2-[(3-Methylbutyl)amino]-2-oxo-1-(phenylmethyl)ethyl]-2-pyrazinecarboxamide