Disclosed is a process for preparing the (R,R)-diastereromer of a compound of formula (VI) or a salt thereof the process comprising: (i) reacting 4-methoxyphenyl acetone with an amine of formula (VIII) under conditions of reductive amination to produce a compound of formula (II) or a salt thereof, wherein there is no isolation of an imine intermediate formed during the reductive amination and wherein the reductive amination is carried out in the presence of an ionic compound in an organic solvent or an aqueous solvent or a mixture thereof, (ii) condensing the (R)-enantiomer of compound (II) or the acid addition salt thereof with an á-haloketone of formula (III) to produce the (R)-enantiomer of a compound of formula (IV) (iii) reducing the (R)-enantiomer of compound (IV) to the (R,R)-diastereomer of a compound of formula (V) and (iv) reducing the (R,R)-diastereomer of compound (V) to the (R,R)-diastereomer of the compound of formula (VI), wherein the reduction is carried out by either (1) a hydrogen donating compound in the presence of a hydrogen transfer catalyst or (2) ammonium formate using a hydrogenation catalyst, wherein: R1 and R2 are independently optionally substituted arylalkyl, and Hal is selected from chloro or bromo. The process is to ultimately synthesis (R,R)-formoterol also known as rac-(R,R)-N-[2-hydroxy-5-[1-hydroxy-2-[1-(4-methoxyphenyl) propan-2-ylamino]ethyl]phenyl]formamide which is also disclosed. Further disclosed is (R,R)-formoterol prepared by the process and a composition comprising formoterol and the use of the formoterol in the manufacture of medicament for treating asthma or chronic obstructive pulmonary disease and a method of treating a non-human patient.
