TUMOUR CHEMOTHERAPY XXIV.THE INTERACTIONS OF ANTIMONOUS ACID WITH THE CHELATING AGENTS RELATED TO ETHYLENEDIAMINETETRAACETIC ACID
Ting‐Chao Chou · Acta Chimica Sinica · 1965
The relative tendency for the formation of the chelates between antimonous acid and the homologue of ethylenediaminetetraacetic acid (Ⅱ) has been investigated from a study of their reduction at the dropping mercury electrode. It was found that for n=2 the chelate (Ⅱ-Sb) should have maximum stability; for n=3 the chelate formed is less stable, while for n3 no antimonial chelate was formed. Two EDTA analogues, namely N-(β-mercaptoethyl) (Ⅳ) and N-(β-aminoethyl) ethylenediaminetriacetic acids (Ⅴ) have been synthesized. The former formed a chelate with antimonous ions, while the latter failed to do so under similar conditions. A series of N-(β-alkyl or aralkyl mercaptoethyl) substituted ethylenetriacetic acids (Ⅵ) and their antimony compounds have been also prepared. The relative stability of these chelates increases with increasing molecular weight of nonchelating substituents in the ligand (see Table 1), thus the influence of steric hindrance on the sulphur atoms was not found. Therefore, it is quite probable that in the antimony chelates of Ⅵ there exists no metal-sulphur bonding. Preliminary pharmacological tests revealed that the antimonous chelates (25 mg/kg) of Ⅵ_b, Ⅵ_c, Ⅵ_e, Ⅵ_g, and Ⅵ_i inhibited the growth of the Ehrlich ascites carcinoma of mice and prolonged the survival period in comparison with the control group.