RESUMO
Evolution of the synthetic strategy that culminated in the first asymmetric total synthesis of the Aspidosperma alkaloid limaspermidine is described. The successful enantioselective route to (-)-limaspermidine proceeds in 10 steps and with the isolation of only six intermediates using a Pd-catalyzed enantioselective decarboxylative allylation we have recently developed. This first enantioselective synthesis of (-)-limaspermidine establishes unambiguously its absolute configuration and allows the first asymmetric formal total synthesis of the Aspidoalbine alkaloid (-)-1-acetylaspidoalbidine.
Assuntos
Alcaloides Indólicos/síntese química , Alcaloides Indólicos/química , Estrutura Molecular , EstereoisomerismoRESUMO
A new class of chiral primary amine catalysts bearing multiple hydrogen-bonding donors have been designed and synthesized. The newly developed bifunctional organocatalysts efficiently catalyzed not only enantioselective conjugate addition of aromatic ketones to nitroolefins in good yields (up to 87%) with excellent enantioselectivities (97â99% ee) but also enantioselective conjugate addition of acetone to nitroolefins in excellent yields (90-96%) with high enantioselectivities (up to 97% ee).
Assuntos
Acetona/química , Alcenos/química , Aminas/química , Cetonas/química , Catálise , Ligação de Hidrogênio , Estrutura Molecular , EstereoisomerismoRESUMO
Biologically important and synthetically challenging spirocyclopentaneoxindoles with four contiguous stereocenters including one spiroquaternary stereocenter have been constructed in good yields (72-87%) with excellent diastereoselectivity (16:1â30:1 dr) and enantioselectivity (93â99% ee) by a combined Ru-catalyzed cross-metathesis/organocatalyzed asymmetric double-Michael addition sequence.
Assuntos
Ciclopentanos/síntese química , Indóis/síntese química , Rutênio/química , Compostos de Espiro/síntese química , Catálise , Técnicas de Química Combinatória , Ciclopentanos/química , Indóis/química , Estrutura Molecular , Oxindóis , Compostos de Espiro/química , EstereoisomerismoRESUMO
A highly diastereo- and enantioselective organocatalytic protocol for the synthesis of biologically important spirocyclopentaneoxindoles containing the oxime functional group from easily accessible 3-allyl-substituted oxindoles and nitroolefins has been developed by a one-pot Michael addition/ISOC/fragmentation sequence.