Synthesis, <i>in vitro</i> biological screening and docking study of benzo[<i>d</i>]oxazole <i>bis</i> Schiff base derivatives as a potent anti-Alzheimer agent

We have synthesized benzo[<i>d</i>]oxazole derivatives (<b>1–21</b>) through a multistep reaction. Alteration in the structure of derivatives was brought in the last step <i>via</i> using various substituted aromatic aldehydes. In search of an anti-Alzheimer agent, all derivatives were evaluated against acetylcholinesterase and butyrylcholinesterase enzyme under positive control of standard drug donepezil (IC₅₀ = 0.016 ± 0.12 and 4.5 ± 0.11 µM) respectively. In case of acetylcholinesterase enzyme inhibition, derivatives <b>8</b>, <b>9</b> and <b>18</b> (IC₅₀ = 0.50 ± 0.01, 0.90 ± 0.05 and 0.3 ± 0.05 µM) showed very promising inhibitory potentials. While in case of butyrylcholinesterase enzyme inhibition, most of the derivatives like <b>6, 8, 9, 13, 15, 18</b> and <b>19</b> (IC₅₀ = 2.70 ± 0.10, 2.60 ± 0.10, 2.20 ± 0.10, 4.25 ± 0.10, 3.30 ± 0.10, 0.96 ± 0.05 and 3.20 ± 0.10 µM) displayed better inhibitory potential than donepezil. Moreover, derivative <b>18</b> is the most potent one among the series in both inhibitions. The binding interaction of derivatives with the active gorge of the enzyme was confirmed <i>via</i> a docking study. Furthermore, the binding interaction between derivatives and the active site of enzymes was correlated through the SAR study. Structures of all derivatives were confirmed through spectroscopic techniques such as ¹H-NMR, ¹³C-NMR and HREI-MS, respectively. Communicated by Ramaswamy H. Sarma