Two novel N-maleanilinic acid derivatives (I-II) namely (E) – oxo -4- ((4- methyl phenyl) amino)-4- oxobut-2-enoic acid (p-MMA) and (E) -4- ((4- methoxy phenyl) amino)-4- oxobut -2- enoic acid (p-MOMA) were prepared by solvent free reaction between maleic anhydride and a p- methyl and p-methoxy aniline derivatives in a good yield. These compounds were synthesized and investigated using elemental analyses, FT-IR and thermal analyses under argon atmosphere. The crystallographic structures of studied compounds were investigated by X-ray diffraction (XRD). The molecular structures of the titled compounds in the ground state were optimized by DFT/B3LYP and HF methods with 6-311G++ (d,p) basis set. Calculations were carried out by GAUSSIAN 09 suite of programs. Natural bond orbitals (NBO) analysis and frontier molecular orbitals were performed using NBO 3.1 program implemented in the Gaussian 09 package are presented at the same level of theory. Thesis results were tabulated. This research aims chiefly to correlate between the structures of these investigated derivatives using experimental techniques in comparison with the theoretical molecular orbital (MO) calculated parameters. This correlation between experimental and theoretical calculations provided a good confirmation of the proposed structures of the newly prepared compounds. The derivatives were found to be highly effective against Hepatocellular carcinoma cells > Breast carcinoma cells > colon carcinoma cells. It was recognized, that cancer cells over expression promotes tumorigenic functions; were suppressed by p-MMA > p-MOMA inhibitors.