The hydrogenation of acetylacetone (I) over asymmetrically modified Raney nickel (MRNi) proceeded, step by step, as follows: acetylacetone (I)\ oversetStep 1→ 4-hydroxy-2- pentanone (II)\ oversetStep 2→ 2, 4-pentanediol (III). It was demonstrated that the optical yield of Step 1 and the diastereomer excess of Step 2 are governed by the ratio of the stereo- differentiating reaction site to the non-stereo-differentiating reaction site on the catalyst. ...