Aspartic acid (I) was esterified with benzyl alcohol to afford the beta-benzyl ester (II). Dakin-West reaction of (II) with Ac2O and Et3N yielded the amido ketone (III). Acidic hydrolysis of (III), followed by re-esterification with EtOH, furnished amino ester (IV), which was acylated with acyl chloride (V), producing amide (VI). Cyclization between the amide and ketone groups of (VI) using Ac2O as the dehydrating reagent gave rise to the isoxazole (VII). The ester group of (VII) was then reduced to alcohol (VIII) with NaBH4 in the presence of AlCl3. Coupling of alcohol (VIII) with 4-nitrophenol (IX) to furnish ether (X) was effected either by Mitsunobu coupling or via previous conversion of (VIII) to the corresponding tosylate, followed by condensation with phenol (IX) under Williamson抯 ether synthesis conditions. Catalytic hydrogenation of the nitro group of (X) led to the aniline (XI). Finally, acylation of (XI) with trifluoromethanesulfonic anhydride provided the target sulfonamide.

Aspartic acid (I) was esterified with benzyl alcohol to afford the beta-benzyl ester (II). Dakin-West reaction of (II) with Ac2O and Et3N yielded the amido ketone (III). Acidic hydrolysis of (III), followed by re-esterification with EtOH, furnished amino ester (IV), which was acylated with acyl chloride (V), producing amide (VI). Cyclization between the amide and ketone groups of (VI) using Ac2O as the dehydrating reagent gave rise to the isoxazole (VII). The ester group of (VII) was then reduced to alcohol (VIII) with NaBH4 in the presence of AlCl3. Coupling of alcohol (VIII) with 4-nitrophenol (IX) to furnish ether (X) was effected either by Mitsunobu coupling or via previous conversion of (VIII) to the corresponding tosylate, followed by condensation with phenol (IX) under Williamson抯 ether synthesis conditions. Catalytic hydrogenation of the nitro group of (X) led to the aniline (XI). Finally, acylation of (XI) with trifluoromethanesulfonic anhydride provided the target sulfonamide.