Tofacitinib Impurity 268

3- ((3R,4R) -3- ((7-hydroxy-7H-pyrrolo[2,3-d]pyrimidin-4-yl) (methyl) amino) -4-methylpiperidin-1-yl) -3-oxopropanenitrile--3- ((3S,4S) -3- ((7-hydroxy-7H-pyrrolo[2,3-d]pyrimidin-4-yl) (methyl) amino) -4-methylpiperidin-1-yl) -3-oxopropanenitrile (1/1)