Practical Synthesis of a Potent Bradykinin B1 Antagonist via Enantioselective Hydrogenation of a Pyridyl N-Acyl Enamide

A practical and efficient synthesis of bradykinin B I antagonist I is described. A convergent strategy was utilized which involved synthesis of three fragments: 3, 6, and 7. Cross coupling of fragments 6 and 7 followed by amidation with 3 enabled efficient synthesis of I in 19 steps total, a 35% overall yield from commercially available pyridine 10. The key to the success of the synthesis was the development of a fluorodenitration step to install the fluorine in pyridine 7 and a catalytic enantioselective hydrogenation of N-acyl enamide 9 to set the stereochemistry.