1,2-Dimethyl-hydrazin-1,2-dicarbonsaeure-diaethylester, diethyl 1,2,3,3b,4a,5,6,6,8,8a,8b,9-dodecahydro-1,5-dioxo-4,8,9-metheno-4H-cyclopenta[1,2-a:4,3-a']dipentalene-4,10-dicarboxylate, diethyl 1,2-dimethylbicarbamate, N,N'-Dimethyl-N,N'-diethoxycarbonylhydrazin, diethyl 1,2-dimethyl-1,2-hydrazinedicarboxylate, Diethyl 1,2,3,3b,4a,5,6,7,8,8a,8b,9-dodecahydro-1,5-dioxo-4,8,9-metheno-4H-cyclopenta(1,2-a:4,3-a')dipentalene-4,10-dicarboxylate, 4,8,9-Metheno-4H-cyclopenta(1,2-a:4,4-a')dipentalene-4,10-dicarboxylic acid,1,2,3,3b,4a,5,6,7,8,8a,8b,9-dodecahydro-1,5-dioxo-,diethyl ester, Diethyl 1,2,3,3b,4a,5,6,7,8,8a,8b,9-dodecahydro-1,5-dioxo-4,8,9-metheno-4H-cyclopenta(1,2-a:4,4-a')dipentalene-4,10-dicarboxylate