| Autor: |
Yamada Y; Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan., Yoshinaga R; Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan., Matsui Y; Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan., Nagatomo M; Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan., Fujino H; Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan., Inoue M; Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan. |
| Abstrakt: |
Here, we report new radical-polar crossover reactions of α-alkoxy carbon radicals for constructing highly oxygenated molecules with contiguous stereocenters. The method employs a 370 nm UV light-emitting diode (LED) for the photoexcitation of α-alkoxyacyl telluride, and Et 3 Al as the radical initiator and terminator. First, Et 3 Al and UV LED promoted radical coupling between the α-alkoxyacyl telluride and cyclopentenone via C-Te bond homolysis, CO expulsion, and C-C bond formation. Second, Et 3 Al converted the radical species to the corresponding aluminum enolate. Third, the second C-C bond formation occurred via a polar mechanism: intermolecularly with aldehydes/ketones and intramolecularly with epoxide, producing aldol and S N 2 adducts, respectively. The present coupling reactions increase the molecular complexity in a single step by stereoselective formation of the two hindered C-C bonds. The devised method is expected to be useful for the expeditious assembly of densely oxygenated natural products. |
