pot heterogeneous synthesis of Δ3-THC from orcinol (1a) and pulegone (2). Four Δ3-THC analogues and corresponding Δ4a-tetrahydroxanthenes (Δ4a-THXs) were synthesized regioselectively and showed differential binding affinities for CB1 and CB2cannabinoidreceptors. Here we report for the first time the CB1 receptor binding of Δ3-THC, revealing a more potentreceptor binding affinity for the (S)-(−) isomer