Application of a catalytic palladium biaryl synthesis reaction, via C-H functionalization, to the total synthesis of Amaryllidaceae alkaloids |
| |
Authors: | José C Torres |
| |
Institution: | Departamento de Química Orgânica, Bloco A, Instituto de Química, Universidade Federal do Rio de Janeiro, Ilha do Fundão, CEP 21945-900 Rio de Janeiro, Brazil |
| |
Abstract: | The total synthesis of the Amaryllidaceae alkaloids dehydroanhydrolycorine, hippadine, pratosine, anhydrolycorine, assoanine, anhydrolycorin-7-one and oxoassoanine was achieved from the appropriate N-benzylisatin precursors using an intramolecular, palladium catalyzed, dehydrohalogenation, biaryl synthesis reaction to establish the carbon skeleton of the natural products. In order to avoid the formation of regioisomers in the cyclization reactions it was found necessary to incorporate the halogen on the benzyl group. Borane reduction of the 7H-pyrrolo3,2,1-de]phenanthridine-4,5-dione derivatives gave 7H-pyrrolo3,2,1-de]- and 4,5-dihydro-7H-pyrrolo3,2,1-de]-phenanthridines (dehydroanhydrolycorine, dehydroassoanine, anhydrolycorine and assoanine). The former were readily reduced to the latter with NaCNBH3 to give anhydrolycorine and assoanine. These compounds were then oxidized to anhydrolycorin-7-one and oxoassoanine whilst the same mixtures of borane reduction products could be oxidized to give hippadine and pratosine. |
| |
Keywords: | Amaryllidaceae alkaloids Pyrrolophenanthridine Biaryl synthesis Palladium catalysis Dehydrohalogenation C-H activation C-H functionalization Indoledione |
本文献已被 ScienceDirect 等数据库收录! |
|