Compounds with activity at serotonin (5‐hydroxytryptamine) 5‐HT 2 and α 1 adrenergic receptors have potential for the treatment of central nervous system disorders, drug addiction or overdose. Isolaureline, dicentrine and glaucine enantiomers were synthesized, and their in vitro functional activities at human 5‐HT 2 and adrenergic α 1 receptor subtypes were evaluated. The enantiomers of isolaureline and dicentrine acted as antagonists at 5‐HT 2 and α 1 receptors with (R)‐isolaureline showing the greatest potency (pK b = 8.14 at the 5‐HT 2C receptor). Both (R)‐ and (S)‐glaucine also antagonized α 1 receptors, but they behaved very differently to the other compounds at 5‐HT 2 receptors: (S)‐glaucine acted as a partial agonist at all three 5‐HT 2 receptor subtypes, whereas (R)‐glaucine appeared to act as a positive allosteric modulator at the 5‐HT 2A receptor.