Strychnos 1990 - 2004 - Crops for the Future

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Author Title Year Source title Reference Mitaine-Offer, A. C., M. Sauvain, A. Valentin, J. Callapa, M. Mallie and M. Zech Antiplasmodial activity of aspidosperma indole alkaloids 2002 Phytomedicine 9(2): 142-145 Abstract The antiplasmodial activity of twelve alkaloids with an aspidospermane skeleton was estimated in vitro on chloroquine-resistant and sensitive strains of Plasmodium falciparum. Seven tetracyclic alkaloids possessing a free ethyl chain such aspidospermine, showed IC50 after incubation for 72 h between 3.2 and 15.4 muM. Moreover, four pentacyclic alkaloids with ethyl chain included in a tetrahydrofuran, such haplocine, showed a reduced activity, with IC50, after 72 h, between 22.6 and 52.6 muM. According to these results, a chloroquine-potentiating experiment was also performed with two of the most active compounds. Isobolograms were obtained and demonstrated a synergic effect of N-formyl-aspidospermidine and aspidospermine when associated with chloroquine. The cytotoxicity and the selectivity index of some alkaloids were also estimated. Author Title Year Source title Reference Abstract Ohshima, T., J. Y. Xu, R. Takita, S. Shimizu, D. F. Zhong and M. Shibasaki Enantioselective total synthesis of (-)-strychnine using the catalytic asymmetric m 2002 Journal of the American Chemical Society 124(49): 14546-14547 -
Author Title Year Source title Reference Padwa, A., T. M. Heidelbaugh, J. T. Kuethe, M. S. McClure and Q. Wang Tandem pummerer/mannich cyclization cascade of alpha-sulfinylamides as a meth 2002 Journal of Organic Chemistry 67(17): 5928-5937 Abstract A series of alpha-sulfinylenamides was conveniently prepared by the condensation of a primary amine with a ketone, followed by reaction of the resulting imine with ethylsulfenylacetyl chloride and subsequent oxidation with sodium periodate. When treated with p-TsOH, cyclization occurred to produce fused isoquinoline lactams by a mechanism that involves an initial Pummerer reaction followed by a subsequent cyclization of the resulting N-acyliminium ion onto the tethered aromatic ring. The isolation of a single diastereomer was rationalized in terms of a Nazarov-type 4pielectrocyclic reaction followed by pi-cyclization onto the least hindered side of the N-acyliminium ion. Another method that was used to generate the alpha-acylthionium ion intermediate involved the reaction of bis(ethylsulfenylacetyl)acetamides with dimethyl(methyl)thiosulfonium tetrafluoroborate (DMTSF). Treatment of several bis-ethylsulfenylenamides with DMTSF delivered novel spiroheterocycles as single diastereomers in good yield by a related process. The convergency and stereochemical control associated with this cascade sequence make it particularly suited for the assembly of natural product scaffolds. Some preliminary studies were directed toward both mesembrine and deethylibophyllidine. When the model Z-enamido sulfoxide 33 was heated with p- TsOH, a 80% yield of tosylate 34 was obtained as a single diastereomer. In this case, the carbocation intermediate derived from cyclization onto the terminal pi-bond was trapped with p-TsOH from the least hindered face, opposite the angular carbomethoxy and methyl groups. Related cyclization cascades were also found to occur with systems containing tethered indole rings. Author Title Year Source title Reference Abstract Philippe G; Prost E; Nuzillard JM; Zeches-Hanrot M; Tits M; Angenot L; Frederi Strychnohexamine from Strychnos icaja, a naturally occurring trimeric indolomon 2002 Tetrahedron Letters 43(18): 3387 - 3390 -
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Strychnos 1990 - 2004 - Crops for the Future

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