1 2 3 5 6 7 hexahydro s indacene July 8, 2019 16 32 64 128 1 2 3 5 6 7-hexahydronaphthalene 1h-indene 2 3 3a 4 7 7a-hexahydro-2 2 4 4 7 7-hexamethyl-