Synthesis of racemic hexahydropyrrolo[1,2-a]quinoline derivatives (1-8) was performed by utilizing the Knoevenagel-[1,5]-hydride shift-cyclization domino reaction. Separation of the enantiomers of the chiral products (1-8) was carried out by chiral high-performance liquid chromatography, and online high-performance liquid chromatography-electronic circular dichroism (ECD) spectra were recorded to elucidate the absolute configuration by comparing the experimental and time-dependent density functional theory-ECD spectra obtained at various theoretical levels. For 1 of the products, the time-dependent density functional theory-ECD calculations allowed determining both the relative and the absolute configuration by distinguishing the 4 stereoisomers. One of the compounds with spiro 1,3-cyclohexanedione moiety (7) possessed moderate acetylcholinesterase inhibitory activity, while 3 showed neuroprotective activity in oxygen-glucose deprivation-induced neurotoxicity in human neuroblastoma SH-SY5Y cells.
Keywords: C-H activation; [1,5]-hydride shift; density functional theory; relative and absolute configuration.
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