THE 1ST ENANTIOSELECTIVE TOTAL SYNTHESES OF THE ALLOPUMILIOTOXIN-A ALKALOID-267A AND ALKALOID-339B

Short, highly stereocontrolled, asymmetric total synthesis of the title amphibian alkaloids are described. In the first stage the indolizidine ketone 11 is assembled from L-proline in enantiomerically pure form. This short sequence proceeds in five laboratory operations and involves the novel intermediacy of an "unprotected" 2-acylpyrrolidine intermediate (Scheme VII). The (Z)-alkylidene side chain of the target alkaloids are introduced by stereocontrolled aldol dehydration sequences (Schemes X and XI). These enantioselective total syntheses confirm the structures and absolute configurations of the allopumiliotoxins 267A and 339B.