benzofurans and lycoramine

An efficient strategy using Rh(I)-catalyzed [(3 + 2) + 1] cycloaddition of 1-ene-vinylcyclopropane and CO as a key step to build the cis-hydrodibenzofuran skeleton has been developed and applied for the formal synthesis of (±)-galanthamine and (±)-lycoramine.

Topics: Amaryllidaceae Alkaloids; Benzofurans; Catalysis; Cycloaddition Reaction; Galantamine; Molecular Structure; Rhodium; Stereoisomerism; Vinyl Compounds

The catalytic asymmetric total syntheses of (-)-galanthamine (1) and (-)-lycoramine (2) have been achieved by using a conceptually new strategy featuring two metal-catalyzed reactions as the key steps. A new method for the construction of 3,4-fused benzofurans has been developed through a palladium-catalyzed intramolecular Larock annulation reaction, which was successfully applied to the construction of the ABD tricyclic skeleton of 1 and 2. To achieve the asymmetric synthesis of 1 and 2, a Sc(III)/N,N'-dioxide complex was used to catalyze the enantioselective conjugate addition of 3-alkyl-substituted benzofuranone to methyl vinyl ketone for the construction of a chiral quaternary carbon center.

Topics: Amaryllidaceae Alkaloids; Benzofurans; Biological Products; Catalysis; Galantamine; Palladium; Stereoisomerism

Divergent route: a direct C-C bond-forming approach to the key aryl-substituted all-carbon quaternary stereogenic center present in bioactive hydrodibenzofuran alkaloids has been discovered. This approach involves an unprecedented organocatalytic enantioselective Michael addition of α-cyanoketones with acrylates and was used in a novel and divergent synthetic strategy for the title compounds in asymmetric fashion.

Topics: Alkaloids; Amaryllidaceae Alkaloids; Benzofurans; Brassicaceae; Carbon; Catalysis; Cyclization; Galantamine; Liliaceae; Spermidine; Stereoisomerism