(S)-1-(5-Bromo-4-methylpyridin-2-yl)ethanamine Hydrochloride is used in the preparation of 3-pyrimidin-4-yl-oxazolidin-2-ones as mutant IDH protein inhibitors. These inhibitors may be used in the treatment of diseases or disorders associated with such mutant IDH proteins including cell-proliferation disorders, such as cancer.