Fig. (7) Chemical structures of compound 3, (1-phenyl-8-[(1S,2S)-2-phenylcyclohexyl]-1,3,8-triazaspiro[4.5]decan-4-one), compound 4, (8- [(1S,2R)-2-hydroxy-2-phenylcyclohexyl]-1-phenyl-1,3,8-triazaspiro[4.5]decan-4-one), compound 5, ((4R)-4-phenyl-8-[(1S,2S)-2- phenylcyclohexyl]-2,8-diazaspiro[4.5]decan-1-one), compound 6, ((4R)-8-[(1S,2R)-2-hydroxy-2-phenylcyclohexyl]-4-phenyl-2,8- diazaspiro[4.5]decan-1-one), and compound 7, (4-(4-fluorophenyl)-8-[1-(4-fluorophenyl)cyclohexyl]-2,8-diazaspiro[4.5]decan-1-one).