ORGN 391 |
| Tse-Lok Ho and Wen-Chung Chung. Dept. of Applied Chemistry, National Chiao Tung University, 1001 Tasueh Rd., Hsinchu, Taiwan |
| The pentacyclic indole alkaloid tacamonine contains three asymmetric carbon centers, i.e., at the C/D/E ring junctures and the atom bearing an ethyl group. We have engaged in a synthetic study emphasizing the use of symmetrical precursors. Previously, a stepwise elaboration of the nontryptamine portion of the molecular skeleton from norbornadiene was unsatisfactory due to the generation of the C-3 epimeric product. Now we report a modification of our approach in that we created a pentacyclic intermediate which has correct relative configuration. Thus, the cis-cyclopent-4-ene-1,3-dimethanol obtained from ozonolysis of norbornadiene was tosylated and reacted with tryptamine. Oxidation of the tertiary amine with mercury(II) acetate, followed by reduction with sodium borohydride led to a mixture of the required intermediate and its stereoisomer. The isomer could be converted to the desired compound by submitting to the same oxido-reduction sequence. The double bond of the bridged azabicyclooctane was functionalized by a 1,3-dipolar cycloaddition ptocess and the resulting isoxazolines were cleaved and further reacted with methylenetriphenylphosphorane. Cyclization and hydrogenation completed the synthesis. |
|
Physical Organic, Materials, Heterocycles, Aromatics, Metal-Mediated Reactions
8:00 PM-10:00 PM, Tuesday, September 9, 2003 Hilton New York -- Americas Hall 1, Poster
Division of Organic Chemistry |