Synthesis and cytotoxic evaluation of two novel anthraquinone derivatives

The antitumor activity of dihydroxyanthracenediones such as mitoxantrone on a panel of cancer cell lines during the last 30 years, led investigators to synthesize thousands of anthracycline analogs and test their cytotoxicity to identify compounds superior to the parent drugs in terms of increased therapeutic effectiveness, reduced toxicity or both. To achieve this, new synthesized congeners either have different side arms or have extra rings on their skeletons. Following these studies, we proposed total synthesis of 2-amino-N-[4-(2-amino-3-hydroxy-propionylamino)-9,10-dioxo-9,10-dihydroanthracene-1-yl]-3-hydroxy-propionamide (V) and 6-amino-hexanoic acid [4-(5-amino-pentanoylamino)-9,10-dioxo-9,10-dihydro-anthracen-1-yl]-amide (VI). Acetylation of 1,4-diaminobenzene using acetyl chloride and reaction with phthalic anhydride under a Friedel-Crafts reaction and then cyclization gave 1, 4-diamino-anthraquinone. This compound was reacted with two amino acids (L-serine and 6-amino hexanoic acid) in their ester forms, using ethyl chloroformate as a coupling agent. Hydrolyzing esterified compounds gave their amino substituted derivatives. These compounds with diamine side arms are supposed to provide better intercalation with DNA. Synthesized novel ametantrone derivatives were tested against a panel of cancer cells (KB, Hela, MDA-MB-468 and K562), using MTT assay. The results showed that tested compounds inhibited the growth of cancer cells at micromolar concentrations. However, compound (VI) was more cytotoxic than compound (V) probably because of its longer side chains and better intercalation with DNA.