Dimethylamine → 6-[(4-fluorophenyl)methyl]-4-hydroxy-3,5-dioxo-7,8-dihydro-2H-2,6-naphthyridine-1-carboxylic acid

To methyl 6-(4-fluorobenzyl)-4-hydroxy-3,5-dioxo-5,6,7,8-tetrahydro-2,6-naphthyridine-1-carboxylate (0.178 g, 0.514 mmol) in wet methanol was added N,N-dimethylamine in MeOH (4.0 eq.). The reaction mixture was put in a microwave reactor where it was heated at 130° C. for 1.5 hours, after which the reaction mixture was concentrated under vacuum. The residue was purified by reverse phase HPLC eluting with 5%-95% acetonitrile (0.1% TFA) in H2O (0.1% TFA) to afford the title compound as a solid. Alternatively, the starting material can be treated with LiOH in 1:1:1 THF/MeOH/H2O to give the product.