ASYMMETRIC TOTAL SYNTHESIS OF THE STEMONA ALKALOID (-)-STENINE

Stenine can be extracted from the roots of the Chinese medicinal plant Stemona tuberosa (Stemonaceae), and its structure and absolute config uration were derived by comparison to the major Stemona alkaloid tuber ostemonine. We report the first enantioselective total synthesis of (- )-stenine by a strategy that takes advantage of a diastereoselective e nd-group-differentiating cyclization in the oxidation of L-tyrosine, T he resulting cis-fused indolone is converted to the trans-fused core o f stenine upon reduction of a pi-allylpalladium complex, and by stereo selective introduction of four additional stereocenters, a butyrolacto ne and an azepine ring are attached to this alkaloid building block.