The known 4-hydroxy-1,5-naphthyridine-3-carboxylic acid (I) was decarboxylated to (II) upon refluxing in quinoline. Heating of (II) with POCl3 furnished 4-chloro-1,5-naphthyridine (III), which was converted to amine (IV) by reaction with n-propylamine in pyridine. Curtius rearrangement of 2-methyl-6-benzoxazolecarboxylic acid (V) in the presence of diphenylphosphoryl azide gave isocyanate (VI). Finally, coupling between isocyanate (VI) and amine (IV) provided the title urea.

The cyclization of 3aminopyridine (I) with diethyl ethoxymethylenemalonate (II) in refluxing Dowtherm gives 4-hydroxy-1,5-naphthyridine-3-carboxylic acid ethyl ester (III), which is hydrolyzed with NaOH in refluxing water to yield the corresponding hydroxyacid (IV). The decarboxylation of (IV) by heating at 320 C in mineral oil affords 4-hydroxy-1,5-naphthyridine (V), which is acylated with trifluoromethanesulfonic anhydride to provide the triflate (VI). The reaction of (VI) with propylamine in pyridine affords 4-amino-1,5-naphthyridine (VII), which is condensed with 2-methylbenzoxazole-6-ylcarbonyl azide (VIII) (obtained by reaction of the corresponding acid (IX) with DPPA) in refluxing toluene to provide the target urea.

The cyclization of 3aminopyridine (I) with diethyl ethoxymethylenemalonate (II) in refluxing Dowtherm gives 4-hydroxy-1,5-naphthyridine-3-carboxylic acid ethyl ester (III), which is hydrolyzed with NaOH in refluxing water to yield the corresponding hydroxyacid (IV). The decarboxylation of (IV) by heating at 320 C in mineral oil affords 4-hydroxy-1,5-naphthyridine (V), which is acylated with trifluoromethanesulfonic anhydride to provide the triflate (VI). The reaction of (VI) with propylamine in pyridine affords 4-amino-1,5-naphthyridine (VII), which is condensed with 2-methylbenzoxazole-6-ylcarbonyl azide (VIII) (obtained by reaction of the corresponding acid (IX) with DPPA) in refluxing toluene to provide the target urea.