The quinolinecarboxylic acid (III) was obtained by the Pfitzinger reaction of isatin (I) with 2-methoxyacetophenone (II) in ethanolic KOH at 80 C. Subsequent methyl ether cleavage in (III) using concentrated HI provided 3-hydroxy-2-phenylquinoline-4-carboxylic acid (IV). Coupling of acid (IV) with (S)-1-phenylpropylamine (V) by means of DCC and HOBt gave amide (VI). Ester (VIII) was then obtained by alkylation of the 3-hydroxy quinoline (VI) with ethyl bromoacetate (VII) in the presence of K2CO3 and KI. Finally, hydrolysis of the ethyl ester (VIII) with refluxing HCl afforded the corresponding carboxylic acid.
Condensation of isatin (I) with 2-methoxyacetophenone (II) in the presence of KOH afforded quinolinecarboxylic acid (III). Subsequent demethylation of the ether function of (III) with refluxing 57% HI gave (IV), which was then condensed with (S)-1-phenylpropyl amine (V) using DCC and HOBt to yield the title amide.