1,2-Piperidinedicarboxylic Acid 1-(Phenylmethyl) Ester is used to prepare disubstituted azetidinones as selective inhibitors of cysteine protease cathepsin K. It is also used to synthesize 2-[(R)-2-methylpyrrolidin-2-yl]-1H-benzimidazole-4-carboxamide (ABT-888) as the Poly(ADP-ribose) Polymerase (PARP) inhibitor for the treatment of cancer.