ABSTRACT
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.
Subject(s)
Indole Alkaloids/chemical synthesis , Indole Alkaloids/chemistry , Molecular Structure , StereoisomerismABSTRACT
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).
Subject(s)
Acetone/chemistry , Alkenes/chemistry , Amines/chemistry , Ketones/chemistry , Catalysis , Hydrogen Bonding , Molecular Structure , StereoisomerismABSTRACT
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.
Subject(s)
Cyclopentanes/chemical synthesis , Indoles/chemical synthesis , Ruthenium/chemistry , Spiro Compounds/chemical synthesis , Catalysis , Combinatorial Chemistry Techniques , Cyclopentanes/chemistry , Indoles/chemistry , Molecular Structure , Oxindoles , Spiro Compounds/chemistry , StereoisomerismABSTRACT
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.
