Treatment of 3-nitro-7-hydroxyquinoline (I) with NaH and benzyl bromide (A) provides benzyloxyderivative (II), which is reduced with SnCl4 in HCl/EtOH to yield (III). Amine (III) is then converted into (IV) via the diazonium salt by treatment with NaNO2 in HCl followed by reaction with methyl acrylate (B) in presence of CuO. Cyclization of (IV) with thiourea in 2-methoxyethanol in presence of NaOAc affords imino-thiazolidinone (V), which is finally hydrolyzed with HCl and EtOH.