Synthesis of a Tetrahydronaphthyridine Spiropyrimidinetrione DNA Gyrase Inhibiting Antibacterial Agent - Differential Substitution at all Five Carbon Atoms of Pyridine.

The synthesis of (−)-1, a potent antibacterial agent, was achieved stereoselectively in nine steps from readily available starting materials. Directed metalations were developed to assemble a pentasubstituted pyridine with appropriately positioned aldehyde and dimethylmorpholine substituents for a key tertiary amino effect reaction (T-reaction) that led to the spirocylic architecture. Ultimately, (−)-1 was isolated as the thermodynamically most favored stereoisomer.