Patent ID: 8853456

Claim:
A process for the preparation of 3-[(R2R,3R)-1-(dimethylamino)-2-methylpentan-3-yl]phenol of Formula-I or its pharmaceutically acceptable salt, said process comprising: a) reacting (S)-1-(dimethylamino)-2-methylpentan-3-one of Formula-VIII with 3-bromo anisole of Formula-II under Grignard reaction conditions to obtain the compound (2S,3R)-1-(dimethylamino)-3-(3-methoxyphenyl)-2-methyl pentan-3-ol of Formula-V; and b) activating the —OH group of (2S,3R)-1-(dimethylamino)-3-(3-methoxyphenyl)-2-methyl pentan-3-ol with methanesulfonic acid or para-toluenesulfonic acid in the presence of a solvent and a mineral acid to obtain an activated compound of Formula IX where R=−SO 2 CH 3 or R=—SO 2 C 5 H 4 CH 3 ; and c) demethylating the activated compound to obtain 3-[(2R,3R)-1-(dimethylamino)-2-methylpentan-3-yl]phenol of Formula-I.