4-?(Chloromethyl)?-?1,?3-?dimethyl-?1H-?pyrazole-?5-?carboxylic Acid Methyl Ester is an intermediate in synthesizing Clenproperol-d7 (C573002). A labelled related drug of Clenbuterol (C569998), a β-agonist which can be used as a growth promoter in farm animals.