1,?2-?Piperidinedicarboxyl?ic 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.