Synthesis and evaluation of 4-amino-substituted 7-methoxy (and 7-hydroxy)- 11-methyl (and 5,11-dimethyl)-10H-pyrido [2,3-b] carbazoles and 4-amino- substituted 11-methyl (and 5,11-dimethyl)-10H-pyrido[3',4':4,5] pyrrolo [3,2-g] quinolines, two new series related to antitumor ellipticine derivatives

Abstract

2-Acetyl-4-chloro-3-lithiopyridine ethylene glycol ketal (6b) was reacted with 3-formyl-5-methoxy-1-methyl-indole (9) and 3-formyl-1-methyl-1H-pyrrolo [3,2-c] pyridine (12), giving the corresponding expected alcohols. Reduction of these intermediates with triethylsilane trifluoroacetic acid and subsequent cyclodehydration then led to 4-chloro-7-methoxy-10,11-dimethyl-10H-pyrido [2,3-b] carbazole (8a) and the corresponding 7-aza-analog (8b). The synthesis of 4-chloro-11-methyl (and 5,11-dimethyl)-10-unsubstituted derivatives of these two series was performed through an independent pathway, involving condensation of conveniently substituted 2-amino carbazoles (17) and 7-amino-5H-pyrido [4,3-b] indoles (18) with 5-(ethoxymethylene)-2,2-dimethyl-1,3-dioxane-4,6-dione, thermal cyclization of the resulting compounds with concomitant decarboxylation to the corresponding tetracyclic fused-4-quinolone systems and final chlorination with phosphorus oxychloride. Nucleophilic substitution of various 4-chloro derivatives was then easily performed in an excess of the required dialkylamino alkylamines at reflux and 4-amino substituted-7-hydroxy-10H- pyrido [2,3-b] carbazoles (25d-e) were obtained from 7-methoxy precursors (25a-b), by demethylation with boron tribromide in methylene chloride at -65 degrees C or with boiling 47% hydrobromic acid. Cytotoxicity determination of all new aminosubstituted derivatives and in vivo antitumor evaluation of the most active compounds clearly show that these two series of ellipticine analogs closely related to highly active products are devoid of antitumor properties in two experimental models shown to be sensitive to ellipticines. The place of the pyridinic nitrogen atom in these series has thus been demonstrated to play a crucial role in antitumor activity.