Functionalization of 1,3-Diisopropylbenzene to Probe the Antagonism of Propofol Anesthesia

General anesthetics like propofol are widely used, but their molecular mechanisms remain poorly understood, limiting the rational design of novel anesthetics or antagonists to enhance safety. We evaluated nine propofol derivatives for their ability to immobilize, or modulate propofol-induced immobilization, in larval zebrafish, using spontaneous and elicited movement as distinct endpoints. We hypothesized that compounds unable to act as hydrogen-bond donors would antagonize immobilization─evidenced by rightward EC₅₀ shifts─while hydrogen-bond-capable derivatives would retain immobilizing effects. Results confirmed that nondonor analogues antagonized propofol's effects, whereas donor molecules had sedative activity, and a hydrocarbon control did not shift the EC₅₀ curve. Quantum-mechanical calculations of hydrogen-bond acidity were correlated to behavioral outcomes, supporting their predictive potential. Notably, a tertiary amine analogue (PEARL 6, N,N-dimethyl-2,6-diisopropylaniline) antagonized most strongly (25.6-fold increase in propofol's EC₅₀ for spontaneous movement and a 1.86-fold increase for elicited movement) without causing excitation when administered alone. These findings identify structural features that distinguish sedative from antagonistic activity and provide characterization of a key feature of propofol derivatives.