This compound can be obtained by several related ways: 1) The hydrolysis of ethyl indoline 2 carboxylate (I) with KOH in aqueous DMSO gives indoline 2-carboxylic acid (II), which is acylated with 3-(benzoylthio)-2-methylpropanoyl chloride (III) in methylene chloride yielding 1-[3-(benzoylthio)-2-methyl-1-oxopropyl]indoline-2-carboxylic acid (IV). Finally, this compound is debenzoylated by treatment with 2-methoxyethylamine (A). 2) The acylation of (I) with methacryloyl chloride (V) by means of triethylamine in ether yields ethyl 1-methacryloylindoline-2-carboxylate (VI), which is hydrolyzed with KOH in aqueous DMSO affording 1-methacryloylindoline-2-carboxylic acid (VII). Finally, this compound is treated with thiobenzoic acid (VIII) and 4-dimethylaminopyridine in acetone to give (IV), previously synthesized. 3) The acylation of acid (II) with (V) as before also gives (VII).
The esterification of indoline-2-carboxylic acid (I) with ethanol HCl gives the corresponding ethyl ester (II), which is acylated with 3-(benzoylthio)-2-methylpropionyl chloride (III) by means of K2CO3 in methylene chloride yielding ethyl N-[3-(benzoylthio)-2-methylpropionyl]indoline-2-carboxylate (IV). The deprotection of (IV) with hydrazine in the same solvent affords ethyl N-(3-mercapto-2-methylpropionyl)indoline-2-carboxylate (V), which is finally saponified with KOH in methanol water.