1 40H (1r,4s,5s,6s)-4-aminospiro[bicyclo[3.1.0]hexane-2,1'-cyclopropane]-4,6-dicarboxylic acid 1.000 2 40F (1s,2s,5r,6s)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid 0.867