Benzyl 4-Phenylbutanoate is an intermediate in the synthesis of Namino-{3-[(R)-1-(3-(4-Amino-3-(4-phenoxyphenyl)-1H-pyrazolo[3,4-d]pyrimidin-1-yl)piperidin-1-yl]-propionyl} Ibrutinib (A619015), which is an impurity of Ibrutinib (I124970), a highly selective Bruton’s tyrosine kinase (Btk) irreversible inhibitor.