1,2,3-trimethyl-3-(2-R-phenylallyl)-4-methylenecyclobutene
1,2,3,4-tetramethylcyclopenta-1,3-diene
3-(2-biphenylyl)-1,2,3-trimethyl-4-methylenecyclobuten
1,2,4-Trimethyl-4-trideuteriomethyl-3-methylencyclobuten
[2-(1,2,3-Trimethyl-4-methylene-cyclobut-2-enyl)-ethyl]-benzene