Abstract: It has been shown that the alkoxyl moiety of β-ethoxy-α-keto-n-butyraldehyde bis-thiosemicarbazone (C6323) can be varied without much effect on its antitumor activity. The synthesis of β-phthalimido-α-keto-n-butyraldehyde in which phthalimido group replaced the ethoxyl group of β-ethoxy-α-keto-n-butyraldehyde (Kethoxal)is described. Derivatives of the title compound, bis-thiosemicarbazone Ⅶ (Ⅴ6133), his-semi carbazone Ⅷ, condensation product. Ⅸ with p-aminobenzoic acid, and 2-α-phthalimidoethyl-1,4-quinoxazoline Ⅹ were prepared. Compound Ⅶ (Ⅴ6133) exhibited marked antitrachomatous (Yu-2) activity at a minimum inhibition concentration of 0.5μg/ml in vitro and was also highly effective against Walker 256 carcinoma in rats. Clinical trials indicated that the compound Ⅶ (Ⅴ6133) is a useful drug in the treatment of infectious trachoma in human.