Patent ID: 7405301

Claim:
A method for N-demethylating an N-methyl morphinane selected from compounds of formulae (i), (ii) and (iii): wherein R and R 1 are independently a hydrogen, methyl or ethyl group, R 2 and R 3 together form a carbonyl or a ═CH 2 group, R 4 is hydrogen and R 5 is hydrogen or a hydroxy group and is an optional double bond; or R 2 is methoxy or hydroxy, R 3 and R 5 together form an ethylene or ethenyl group and R 4 is a hydroxy or keto-substituted straight or branched C 1-6 alkyl group; or a protected derivative thereof, comprising the steps of: (i) treating said N-methyl morphinane with an oxidising agent to form the N-oxide morphinane; and (ii) treating said N-oxide morphinane with a reducing agent.