A mixture of 6-(3-chloro-4-fluorobenzyl)-3,4-dihydroxy-N,N-dimethyl-5-oxo-5,6,7,8-tetrahydro-2,6-naphthyridine-1-carboxamide (0.15 g, 0.39 μmmol; Example 1, Step 9) and magnesium methoxide in methanol (2 mL, 6-10% methanol solution available from Aldrich) in DMSO (4 mL) was heated at 60° C. for 30 minutes. Methanol was exhaustively removed under vacuum over 45 minutes. The resultant DMSO solution was treated with 1-bromo-2-chloroethane (0.28 g, 1.97 mmol) and stirred at 60° C. under an atmosphere of nitrogen overnight. The reaction mixture was diluted with ethyl acetate and dilute hydrochloric acid. The organic extract was washed with aqueous sodium sulfite, brine, dried over anhydrous sodium sulfate, filtered, and concentrated under vacuum. The residue was purified by reverse phase high pressure liquid chromatography. Collection and lyophilization of appropriate fractions provided the title compound, which was recrystallized from a mixture of ethyl acetate and hexane
