A process for the preparation of a compound of formula (I) such as 2(R)-4-oxo-4-[3-(trifluoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-a]-7(8H)-pyrazinyl]-1-(2,4,5-trifluorophenyl)-2-butanamine, or a salt thereof, in the anhydrous or hydrated form, either as a mixture of enantiomers, or as a single (R) or (S) enantiomer, comprising the conversion of a compound of formula (II), or a salt thereof, either as a single (R) or (S) enantiomer or as a mixture thereof wherein X is hydrogen, hydroxy, C1-C8 alkyl, C1-C4 alkoxy, aryl, amino, N3 or halogen; into a compound of formula (I), and if desired, the separation of a single enantiomer of formula (I) from the racemic mixture, and/or, if desired, the conversion of a compound of formula (I) into a salt thereof, or vice versa.