Condensation of veratraldehyde (I) with malonic acid and ammonium acetate in refluxing EtOH afforded 3-amino-3-(3,4-dimethoxyphenyl)propionic acid (II). The N-phthaloyl group was introduced in (II) by treatment with N-carbethoxyphthalimide (III) in the presence of Na2CO3. The resulting phthalimido acid (IV) was converted to the title amide via activation with carbonyl diimidazole, followed by treatment with ammonium hydroxide.
Condensation of 3,4-dimethoxybenzaldehyde (I) with malonic acid (II) in the presence of ammonium acetate afforded 3-amino-arylpropionic acid (III), which was esterified with MeOH and SOCl2 to give (IV). Finally, condensation with tetrafluorophthalic anhydride (V) in refluxing AcOH provided the target phthalimide.