Synthesis and evaluation of 2,3,4,9-tetrahydro-1H-carbazole derivatives as selective acetylcholinesterase inhibitors: Potential anti-Alzheimer’s agents

Abstract

Alzheimer’s disease is an irreversible, progressive brain disorder that slowly destroys memory and cognition skills. Dysfunction of acetylcholine containing neurons in the brain contributes substantially to the cognitive decline observed in Alzheimer's disease. Hence, our focus is to synthesize cholinesterase inhibitors. A series (22 compounds) of 6- and 9-substituted derivatives of 2,3,4,9-tetrahydro-1<em>H</em>-carbazole have been prepared and <em>in vitro</em> evaluated for acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibition by Ellman’s method. By comparing selectivity with standard drug donepezil, amino derivative <strong>3</strong>, methylamino derivative <strong>4</strong> and butyl nitro derivative <strong>17</strong> have been found to be selective AChE inhibitors. Borsche-Drechsel cyclization reaction has been carried out to synthesize 2,3,4,9-tetrahydrocarbazole ring followed by nitration, reduction and derivative synthesis.