Compounds of the formula (II) can be hydrogenated to the corresponding butane derivatives in the presence of homogeneous catalysts comprising metal salts or complexes containing metals from the group consisting of Rh, Ir and Ru and preferably containing diphosphine ligands, with, in addition, excellent optical yields being achieved when one of R2 and R3 is not an H atom and the diphosphine ligand is chiral.