1-(4′-Hydroxymethyl-phenyl)-2-methyl-3-(piperidine-1-yl)-propane-1-one M2, a metabolite of tolperisone, was synthesised in a solvent-free Mannich reaction. The optical resolution was carried out by diastereoisomeric salt formation and separation, for which three resolving agents ((2R,3R)-O,O′-dibenzoyl tartaric acid, (2R,3R)-O,O′-di-p-toluoyl tartaric acid and (R)-2-hydroxy-4-(2-methoxyphenyl)-5,5-dimethyl-1,3,2-dioxaphosphorinane-2-oxide (anicyphos)) were found. The absolute configuration of M2 was determined by the single-crystal X-ray diffraction method.