The inhibition effects of L (-) aspartic acid (I) and its various derivatives namely N-benzenesulphonyl L (-) aspartic acid (II), alpha-benzenesulphonamido-beta-2-(1, 4, 5, 6-tetrahydropyrimidinyl) propionic acid (III) and 1-benzenesulphonamido-1, 2-bis-2(1,4,5,6-tetrahydropyrimidinyl) ethane (IV) against the corrosion of brass in 0.6 M aqueous sodium chloride solution have been studied using potentiodynamic polarization and electrochemical impedance spectroscopy. The inhibition efficiency of these compounds increases in the order I < II < III < IV. The inhibition efficiency of IV with 4 x 10 (-5) M concentration is the highest which reaches 94.9%. It is observed that the introduction of C6H5SO2- group increases the inhibition efficiency of L (-) aspartic acid by 32.0%. Conversion of one -COOH group to 1, 4, 5, 6-tetrahydropyrimidine increases inhibition efficiency by 15.5% and when both the -COOH groups are converted to 1,4,5,6 tetrahydropyrimidine the inhibition efficiency becomes maximum (95%). This is due to higher molecular size, pi - electron contribution of the benzene ring, and presence of more active adsorption sites.