Benzyl 4-chloroanthranilate (I) is treated with phenyl chloroformate in hot dioxane to produce carbamate (II). Condensation between the phenyl carbamate (II) and sulfonamide (III) in the presence of DBU yields the sulfonyl urea (IV). The benzyl ester and N-benzyloxycarbonyl groups of (IV) are then removed by catalytic hydrogenolysis to furnish acid (V). Cyclization of (V) by means of CDI leads to the quinazolinedione (VI). Finally, the tert-butyl ester group of (VI) is cleaved by treatment with trifluoroacetic acid to provide the title compound