A series of chloro- and aminoalkylamino-substituted neocryptolepine (5-methyl-5H-indolo[2,3-b]quinoline) derivatives were synthesized and evaluated as antiplasmodial agents. The evaluation also included cytotoxicity (MRC5 cells), inhibition of beta-hematin formation, and DNA interactions (DNA-methyl green assay). Introduction of aminoalkylamino chains increased the antiplasmodial activity of the neocryptolepine core substantially. The most efficient compounds showed antiplasmodial activities in the nanomolar range. N(1),N(1)-Diethyl-N(4)-(5-methyl-5H-indolo[2,3-b]quinolin-8-yl)pentane-1,4-diamine 11c showed an IC(50) of 0.01 microM and a selectivity index of 1800.

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9H-a-Carbolines have been prepared via consecutive intermolecular Buchwald-Hartwig reaction and Pd-catalyzed intramolecular direct arylation from commercially available 2,3-dichloropyridines and substituted anilines. The combination of a high reaction temperature (180 8C) and the use of DBU were found to be crucial for the intramolecular direct arylation reactions of the 3-chloro-N-phenylpyridin-2-amines as no reaction was observed at 120 8C and 180 8C using different inorganic and other organic bases. On the other hand, nitrogenmethylated pyridine analogues of these substrates {N-[3-chloro-1-methylpyridin-2(1H)-ylidene]anilines} do undergo ring closure at 120 8C, with K 3 PO 4 as base, affording the respective 1-methyl-1H-a-carbolines in good yields.

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