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 configuration were derived by comparison to the major Stemona alkaloid tuberostemonine. We report the first enantioselective total synthesis of (-)-stenine by a strategy that takes advantage of a diastereoselective end-group-differentiating cyclization in the oxidation of L-tyrosine, The resulting cis-fused indolone is converted to the trans-fused core of stenine upon reduction of a pi-allylpalladium complex, and by stereoselective introduction of four additional stereocenters, a butyrolactone and an azepine ring are attached to this alkaloid building block.