(1S,3S,5S)-2-[(2S)-2-amino-2-(3-hydroxy-1-adamantyl)acetyl]-2-azabicyclo[3.1.0]hexane-3-carbonitrile
(1S,3S,5S)-2-[(2S)-2-amino-2-(3-hydroxy-1-adamantyl)-1-oxoethyl]-2-azabicyclo[3.1.0]hexane-3-carbonitrile
(1S,3S,5S)-2-[(2S)-2-amino-2-(3-hydroxy-1-adamantyl)ethanoyl]-2-azabicyclo[3.1.0]hexane-3-carbonitrile