Abstract: Lycobetaine (AT-1840, I) showed antitumor activity both in vitro and in vivo . Structure activity studies had concluded that in order to keep the activity of I, the intramolecular betaine structure must be kept while the fission of the five membered N-containing ring would not significantly decrease its activity. But one of the analogues of compound I, N-methyl-2-methyl-8,9-methylenedioxy phenanthridinium chloried (II) also showed activity without a betaine structure. It was assumed that N-methyl-2-carboxyl-8,9-methylenedioxy-phenanthridinium chloride (III) was the active metabolite of compound II in vivo . In the present paper, the synthesis of compound III is reported. The procedure of synthesis is shown in the scheme. Preliminary pharmacological tests showed that compound III was inactive both in vitro (P388) and in vivo (Ehrlich ascites carcinoma).