(3R)​-3-​[4-​Amino-​3-​(4-​phenoxyphenyl)​-​1H-​pyrazolo[3,​4-​d]​pyrimidin-​1-​yl]​-1-​piperidinecarboxylic Acid Phenylmethyl Ester is an intermediate in synthesizing Ibrutinib-d4 (I124971), a labelled analogue of Ibrutinib (I124970). Ibrutinib is a highly selective Bruton’s tyrosine kinase (Btk) irreversible inhibitor.