3-Azabicyclo[3.1.0]hexane-2-carboxylic acid,3-[(2S)?-?3,?3-?dimethyl-?1-?oxo-?2-?[(2,?2,?2-?trifluoroacetyl)?amino]?butyl]?-?6,?6-?dimethyl-?,(1R,?2S,?5S)?-