Tofacitinib Impurity 175

Ethyl 4-cyano-3-imino-5-((3R,4R)-4-methyl-3-(methyl(7H-pyrrolo[2,3-d]pyrimidin-4-yl)amino)piperidin-1-yl)-5-oxopentanoate, 5-Oxopentanoate, ethyl 4-cyano-3-imino-5-((3R,4R)-4-methyl-3-(methyl(7H-pyrrolo[2,3-d]pyrimidin-4-yl)amino)piperidin-1-yl)-;