Synthesis of Trelagliptin Succinate

An improved process for the synthesis of antidiabetic drug trelagliptin succinate through unprotected (R)-3-aminopiperidine was described. The impurity profile with different conditions of the key substitution was illustrated, and then the best reaction condition was identified. The optimizations also included the bromination of 4-fluoro-2-methylbenzonitrile so that the process became efficient and concise.