[CH2:1]([OH:8])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.Cl[C:10]1[C:19]2[C:14](=[CH:15][CH:16]=[C:17]([O:20][CH3:21])[N:18]=2)[N:13]=[CH:12][C:11]=1[C:22]([OH:24])=[O:23].[H-].[Na+]>CN(C)C=O>[CH2:1]([O:8][C:10]1[C:19]2[C:14](=[CH:15][CH:16]=[C:17]([O:20][CH3:21])[N:18]=2)[N:13]=[CH:12][C:11]=1[C:22]([OH:24])=[O:23])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1Benzyl alcohol (5.78 g, 53.43 mmol, 2.5 eq) is added at −45° C. to a stirred solution of 4-chloro-6-methoxy-[1,5]naphthyridine-3-carboxylic acid (5.1 g, 21.37 mmol, 1.0 eq) in N,N-dimethylformamide (100 mL), followed by sodium hydride (2.46 g, 53.43 mmol, 2.5 eq). After 2 hours stirring at −40° C. and 24 hours stirring at room temperature, the reaction mixture is quenched with ice water, the pH is adjusted to 3-4 by the addition of a 2N hydrochloric acid aqueous solution. The resulting precipitate is collected by filtration, washed with water and dried under high vacuum to afford 4-benzyloxy-6-methoxy-[1,5]naphthyridine-3-carboxylic acid as a light red solid (6.5 g, 98% yield).
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