Enantioselective imminium and enamine catalyzed pathways have proven to be highly effective means for asymmetric bond constructions. Imminium mediated processes provide unique opportunities for multiple bond constructions in a single synthetic step because of concomitant formation of enamine intermediates. Though examples of both imminium and enamine processes have been extensively documented in the literature, reported cases uniting the two pathways in a domino sequence are rare. It is the intent of this proposal to develop imminium catalzyed asymmetric amine conjugate addition/carbocyclization reactions catalyzed by a single chiral amine organocatalyst. The carbocyclizations of interest are alkylation, aldol, Mannich, and Michael addition processes. This methodology would provide a highly convergent method for the construction of optically active densely functionalized pyrrolidine and piperidine heterocycles. As a final goal of this proposal, the methodology developed will be applied to the total syntheses of the fully- functionalized pyrrolidines plakoridines A and B. Plakoridine A is of particular interest due to its documented cytotoxicity towards murine lymphoma L1210 cells. ? ?
| Nicewicz, David A; MacMillan, David W C (2008) Merging photoredox catalysis with organocatalysis: the direct asymmetric alkylation of aldehydes. Science 322:77-80 |
