4-{3-[2-(5-ethyl-3,6-dihydropyridin-1(2H)-yl)ethyl]-1H-indol-2-yl} 1-methyl 4a-[2-(5-ethyl-3,6-dihydropyridin-1(2H)-yl)ethyl]-9-methyl-3,4,4a,9-tetrahydro-2H-carbazole-1,4-dicarboxylate