Ring-expansion synthesis and crystal structure of dimethyl 4-ethyl-1,4,5,6,7,8-hexahydroazonino-[5,6-b]indole-2,3-dicarboxylate.

The title compound, C₂₀H₂₄N₂O₄, is the product of a ring-expansion reaction from a seven-membered hexahydroazepine to a nine-membered azonine. The azonine ring of the molecule adopts a chair-boat conformation. In the crystal, molecules are linked by bifurcated N--H⋯(O,O) hydrogen bonds, generating [010] zigzag chains. The title compound shows inhibitory activity against acetylcholinesterase and butyrylcholinesterase, and might be considered as a candidate for the design of new types of anti-Alzheimer's drugs. [ABSTRACT FROM AUTHOR]