Strychnos 1990 - 2004 - Crops for the Future

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Author Title Year Source title Reference Padwa, A. and A. G. Waterson The thionium/n-acyliminium ion cyclization cascade as a strategy for the synthesi 2000 Tetrahedron 56(52): 10159-10173 Abstract A series of amidosulfoxides were prepared by the addition of thiophenol to the appropriate alkenoic acid pi -bond, and this was followed by reaction of the in situ generated acyl chloride with 3,4- dimethoxyphenethyl amine. The silicon-induced Pummerer reaction of these amidosulfoxides was carried out using 1-(dimethyl-tert-butylsiloxy)-1-methoxyethylene in dry acetonitrile in the presence of a catalytic amount of ZnI2 and led to the very clean formation of 2-thiophenyl substituted lactams. Iminium ion-aromatic pi -cyclization was accomplished by treatment of the initially formed thiophenyl lactams with BF3.2AcOH which resulted in the generation of an N-acyliminium ion. Cyclization of the iminium ion onto the tethered aromatic ring led to various azapolycyclic ring systems. A related cyclization sequence also occurred with amidosulfoxides that possess simple olefinic tethers. The method was applied toward the synthesis of a member of the protoberberine alkaloid family. (C) 2000 Elsevier Science Ltd. All rights reserved. Author Title Year Source title Reference Abstract Penelle, J., M. Tits, P. Christen, J. Molgo, V. Brandt, M. Frederich and L. Angeno Quaternary indole alkaloids from the stem bark of Strychnos guianensis 2000 Phytochemistry 53(8): 1057-1066 -
Author Title Year Source title Reference Rafatro, H., D. Ramanitrahasimbola, P. Rasoanaivo, S. Ratsimamanga-Urverg, A. Reversal activity of the naturally occurring chemosensitizer malagashanine in Plas 2000 Biochemical Pharmacology 59(9): 1053-1061 Abstract Malagashanine (MG) is the parent compound of a new type of indole alkaloids, the NbC(21)- secocuran, isolated so far from the Malagasy Strychnos species traditionally used as chloroquine adjuvants in the treatment of chronic malaria. Previously, it was shown to have weak in vitro intrinsic antiplasmodial activity (IC50 = 146.5 +/- 0.2 mu M), but did display marked in vitro chloroquine-potentiating action against the FcM29 chloroquine-resistant strain of Plasmodium falciparum. The purpose of the present study was to further investigate its reversal activity. Thus, the previous in vitro results were tested in vivo. The interaction of MG with several antimalarials against various strains of P. falciparum was also assessed. As expected, MG enhanced the effect of chloroquine against the resistant strain W2, but had no action on the susceptible strain 3D7 and two sensitive isolates. interestingly, MG was found to exhibit significant chloroquine-potentiating action against the FcB1 strain formerly described as a resistant strain but one which has since lost its resistance for unknown reasons. One other relevant result that arose from our study was the observation of the selective enhancing action of MG on quinolines (chloroquine, quinine, and mefloquine), aminoacridines (quinacrine and pyronaridine), and a structurally unrelated drug (halofantrine), all of which are believed to exert their antimalarial effect by binding with haematin. MG was finally found to specifically act with chloroquine on the old trophozoite stage of the P. falciparum cycle. Similarities and differences between verapamil and MG reversal activity are b riefly presented. (C) 2000 Elsevier Science Inc.
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