Process for preparing a derivative of 10,11-methanodibenzosuberane.

A process for preparing a compound of formula (IVa) wherein HX is an acid, comprising the steps of: (a) dissolving a compound of formula (II) in acetonitrile to form a solution; (B) crystallizing a stereoisomer compound without of formula (III) solution (II); (C) removing the acetonitrile from the filtrate to provide an enriched in a stereoisomer anti of formula (IV) compound mixture; (D) adding an acid selected from the group consisting of hydrogen, hydrogen bromide and camphorsulfonic acid chloride and a solvent selected from the group consisting of methylene, ethanol and ethyl acetate to said enriched mixture; and (e) crystallizing the anti-stereoisomer of formula (IVa) compound.