synthesized a novel series of piperidine propionamide derivatives as potent sigma-1 (σ1) receptor antagonists and mu (μ) opioid receptor agonists, and measured their affinity for σ1 and μ receptors in vitro through binding assays. The basic scaffold of the new compounds contained a 4-substituted piperidine ring and N-aryl propionamide. Compound 44, N-(2-(4-(4-fluorobenzyl) piperidin-1-yl) ethyl)-N-(4-methoxy-phenyl)