Discovery of 2‐(3,4‐dialkoxyphenyl)‐2‐(substituted pyridazin‐3‐yl)acetonitriles as phosphodiesterase 4 inhibitors with anti‐neuroinflammation potential based on three‐dimensional quantitative structure–activity relationship study

: Phosphodiesterase 4 (PDE4) inhibitors with potential activities for CNS disorders provide a new therapeutic strategy for depression. To discover PDE4 inhibitors with anti-neuroinflammation activities, reliable three-dimensional quantitative structure-activity relationship (3D-QSAR) models on our previous reported catecholic PDE4 inhibitors was built with a statistically significant cross-validated coefficient (q2 ), conventional coefficient (r2 ), and good predictive capabilities based on the molecular docking results, using comparative molecular field analysis (CoMFA) and comparative molecular similarity index analysis (CoMSIA) methods. Based on the analysis of CoMFA and CoMSIA contour maps, a series of 2-(3,4-dialkoxyphenyl)-2-(substituted pyridazin-3-yl) acetonitriles 16a-i was designed and synthesized. Among these compounds, compound 16a exhibited good inhibitory activities toward PDE4B1 and PDE4D7 with mid-nanomolar IC50 values and potential anti-neuroinflammation activity in BV-2 cells. Docking simulation of compound 16a in the PDE4 catalytic domain activity pocket revealed that compound 16a maybe assumed a "V-shaped" conformation, extending the side chain to S-pocket.