Process for the preparation of an optically pure enantiomer of formoterol

A process for the preparation of optically pure (R,R)-N-›2-hydroxy-5-(1-hydroxy-2-((2-(4-methoxyphenyl)-1-methylethyl)amin o)ethyl)phenyl!formamide or the fumarate salt thereof, which process comprises separating the recemic mixture or mixture of diastereoisomers of the free compound in a mobile phase containing a nonpolar solvent and optionally a further polar protic or aprotic solvent by chromatography on a chiral stationary phase consisting of a polysaccharide whose free hydroxyl groups are derivatised by the 4-methylbenzoyl group, and an inert carrier material, and isolating the optically pure R,R compound from the eluate of the mobile phase and convening said compound into the fumarate salt.