synthesis of new 1, 8-dioxo-octahydroxanthene derivatives containing 4-thiazolidinone moiety

A series of novel 1, 8-dioxo-octahydroxanthene derivatives containing 4-thiazolidinone framework (4a-f) were synthesized through a four-step reaction starting from the reduction of nitro derivatives of 1, 8-dioxo-octahydroxanthenes. the resulting aminoxanthenes converted to thiourea derivatives via their reaction with methyl isothiocyanate. the final products were synthesized through the reaction of thiourea derivatives with dialkylacetylene dicarboxylates. all of the steps were carried out under easy and mild reaction conditions in the absence of expensive catalysts or esoteric starting materials. the structures of compounds 3a-c and the final products were characterized according to their physical constants, spectral data such as nmr, ir spectra and also elemental analysis.