2,2'-diphenyloctahydro-1H,1'H-10,10'-spirobi[[5,8]methano[1,2,4]triazolo[1,2-a]pyridazine]-1,1',3,3'(2H,2'H)-tetraone

(1RS,9SR)-11-phenyl-10,12-dioxabicyclo(7.3.0)dodeca-4,5-diene

(1RS,9SR)-11-phenyl-10-oxa-12-thiabicyclo(7.3.0)dodeca-4,5-diene

2,3-diazabicyclo[2.2.1]hept-2-ene-7,5'-spirobicyclo[2.1.0]pentane