Preparation of Saxagliptin, a Novel DPP-IV Inhibitor

The commercial-scale synthesis of the DPP-IV inhibitor, saxagliptin (1), is described from the two unnatural amino acid derivatives 2 and 3. After the deprotection of 3, the core of 1 is formed by the amide coupling of amino acid 2 and methanoprolinamide 4. Subsequent dehydration of the primary amide and deprotection of the amine affords saxagliptin, 1. While acid salts of saxagliptin have proven to be stable in solution, synthesis of the desired free base monohydrate was challenging due to the thermodynamically favorable conversion of the free amine to the six-membered cyclic amidine 9. Significant process modifications were made late in development to enhance process robustness in preparation for the transition to commercial manufacturing. The impetus and rationale for those changes are explained herein.