(c-4a,c-8a)-1,4,4a,5,8,8a-Hexahydro-10,10-dimethyl-r-1,c-4:t-5,t-8-dimethanophthalazin

dimethyl bicyclo[3.2.1]octa-3,6-diene-2,2-dicarboxylate

dimethyl 2-(7-bicyclo[2.2.1]hepta-2,5-dienyl)propanedioate

dimethyl 2-(5-bicyclo[2.2.1]hept-2-enylidene)propanedioate

3,3-dicarbomethoxy-exo-tricyclo[3.2.1.02,4]oct-6-ene