A concise and asymmetric total synthesis of five kopsane alkaloids that share a unique heptacyclic caged ring system was accomplished. The key transformation in the sequence involved a remarkable PtCl2-catalyzed intramolecular [3+2] cycloaddition, which allowed for the rapid assembly of pentacyclic carbon skeletons bearing 2,3-quaternary functionalized indoline. Expeditious construction of diverse indoline scaffolds with excellent control of diastereoselectivity demonstrated the broad scope and versatility of this key transformation. 相似文献
Astrocyte‐nanofiber interactions are studied by culturing primary rat cortical astrocytes on poly[caprolactone‐co‐(ethyl ethylene phosphate)] electrospun nanofibers and solvent‐cast films (two‐dimensional control). The results indicate that nanofiber topography significantly suppresses astrocyte proliferation and enhances apoptosis, without altering cellular activation as compared to films. Moreover, nanofiber topography enhances gene‐silencing efficiency in astrocytes. The results suggest that nanofibers may serve as potential substrates for nerve regeneration by suppressing astrocyte growth and may further facilitate the use of gene‐silencing to enhance CNS regeneration.
A rapid approach to the skeleton of dalesconol A and B, unprecedented immunosuppressants, has been achieved through a convergent strategy featuring a carbocation-mediated dearomatization-cyclization and a following one-pot consecutive operation. 相似文献
A chiral phosphoric acid catalyzed enantioselective bromocyclization of olefins is described. Various cis-, trans-, or trisubstituted γ-hydroxy-alkenes and γ-amino-alkenes can cyclize under the reaction conditions to give optically active 2-substituted tetrahydrofurans and tetrahydropyrroles in up to 91% ee. 相似文献