The condensation of 2-methoxypyridine-3-amine (I) with ethyl 2-(ethoxymethylene)-3-oxohexanoate (II) by heating at 120-30 C gives the aminoacrylate ewster (III), which is cyclized by heating in refluxing diphenyl ether to yield the naphthyridinone (IV). The reaction of (IV) with methanesulfonyl chloride and triethylamine in dichloromethane affords the methanesulfonyloxy naphthyridine (V), which is finally condensed with (R)-1-phenylethylamine (VI) in refluxing acetonitrile.