The hydroxyindolenine 2, upon treatment with Ac2O in pyridine, rearranged into the bridged 16-spiro compound 3. Compound 3 can be considered to be a synthon of the carbocation at C(16) of ibogaine ( 7) since the solvolysis of 3 in EtOH/H2O gave a mixture of the 16-ethoxy- and 16-hydroxyibogaine derivatives 5 and 6, respectively.