合成路线1

3-Bromo-4-methylaniline (I) was converted to the isonitrosoacetanilide (II) upon treatment with chloral hydrate and hydroxylamine. Cyclization of (II) in hot sulfuric acid produced the isatin (III) along with its 6-bromo regioisomer. Anthranilic acid (IV) was then obtained by oxidative cleavage of isatin (III). Esterification of anthranilic acid (IV) was achieved by conversion to the benzoxazinone (V) with acetic anhydride, followed by conversion to methyl anthranilate (VI) in boiling methanol. Alternatively, anthranilic acid (IV) was activated as the isatoic anhydride (VII) with triphosgene and then reacted with MeOH. Anthranilate (VI) was converted to the aminoquinazolinone (IX) upon condensation with chloroformamidine hydrochloride (VIII) at elevated temperature. Coupling of bromide (IX) with methyl 4-mercaptobenzoate (X) under Ullmann reaction conditions furnished thioether (XI). The methyl ester group was then hydrolyzed to the acid (XII) with NaOH in aqueous EtOH.