Phthalazine derivatives attached to amino acid derivatives were synthesized with high yields. The reaction of phthalazine derivatives with different phthalyl and tosylamino acids such as glycine, alanine, phenylalanine, valine, serine, and threonine in the presence of N,N-dicyclo hexylcarbodiimide (DCC) as a dehydrating agent reagent yielded high yields of the afforded compounds.Phthalylamino acids derivatives were obtained by deprotection of phthalazine derivatives, with the latter heating with hydrazine hydrate. The chemical structures of all phthalazine derivatives were affirmed by elemental analysis and spectral data (IR, MS, 1 HNMR, and 13 C NMR). Screening out and estimation of the synthesized derivatives for their cytotoxic and antioxidant activity were done, and most of them showed powerful activity in comparison with standard drugs.We got all chemical reagents from Sigma-Aldrich. Solvents were purchased from El-Nasr Chemicals in analytical grade. Also, we did thin-layer chromatography (TLC) on all products by using silica gel polyester sheets (Kieselgel 60 F254, 0.20 mm, Merck). All melting points are in degree centigrade (uncorrected). We recorded IR spectra (KBr) at the Microanalytical Center (Faculty of S C H E M E 1 Synthesis of phthalazinone derivative 2 S C H E M E 2 Synthesis of phthalazines derivative (4,5) WASFY ET AL.