Catalytic Asymmetric Desymmetrization of Cyclic 1,3-Diketones Using Chiral Boro-phosphates

Herein, we report a chiral boro-phosphate-catalyzed reductive amination for the desymmetrization of 2,2-disubstituted 1,3-cyclopentadiones with pinacolborane as the reducing agent, delivering chiral β-amino ketones with an all-carbon quaternary stereocenter in good yields (≤94%), high enantioselectivities (≤97% ee), and excellent diastereoselectivities (>20:1 dr). This reaction has a broad substrate scope and high functional group tolerance. The importance of the chiral products was also demonstrated through the preparation of multifunctional building blocks and heterocycles.

Enantioselective Total Synthesis of (+)-Garsubellin A

Garsubellin A is a meroterpene capable of enhancing the enzyme choline acetyltransferase whose decreased level is believed to play a central role in the symptoms of Alzheimer's disease. Due to the potentially useful biological activity together with the novel bridged and fused cyclic molecular architecture, garsubellin A has garnered substantial synthetic interest, but its absolute stereostructure has been undetermined. We report here the first enantioselective total synthesis of (+)-garsubellin A. Our synthesis relies on stereoselective fashioning of a cyclohexanone framework and double conjugate addition of 1,2-ethanedithiol that promotes aldol cyclization to build the bicyclic [3.3.1] skeleton. The twelve-step, protecting group-free synthetic route has enabled the syntheses of both the natural (-)-garsubellin A and its unnatural (+)-antipode for biological evaluations.

Copper-Catalyzed Asymmetric Synthesis of Bicyclo[3.n.1]alkenones

A series of highly strained bicyclo[3.n.1]alkenones have been successfully constructed in good-to-excellent enantioselectivities and moderate-to-good yields via copper-catalyzed formal [3+3] cycloaddition. The versatile chiral cycloadducts could be selectively converted into various valuable bridge systems, which hold considerable potential for the construction of natural and bioactive compounds containing a [3.n.1] moiety.

Rh-Catalyzed diastereoselective desymmetrization of enone tethered-cyclohexadienones via tandem arylative cyclization

The rhodium-catalyzed arylative cyclization of enone tethered-cyclohexadienones has been developed with high efficiency, thus providing cis-fused bicyclic enones in good yields and with excellent diastereoselectivities.

Organocatalytic Asymmetric Formal [3+2] Cycloaddition as a Versatile Platform to Access Methanobenzo[7]annulenes

Pharmaceutically and structurally important methanobenzo[7]annulenes were synthesized in very good yields with excellent enantio- and diastereoselectivities through an unprecedented organocatalytic formal [3+2] cycloaddition from readily available 2-alkyl-3-hydroxynaphthalene-1,4-diones and alkyl vinyl ketones.

Carbonyl-assisted reverse regioselective cascade annulation of 2-acetylenic ketones triggered by Ru-catalyzed C-H activation

The first reverse regioselective intermolecular annulation of aryl substituted 2-acetylenic ketones with O-substituted N-hydroxybenzamides or acrylamides followed by tandem cyclization via ruthenium-catalyzed C-H activation, is reported. Excellent reverse selectivity of alkyne insertion was induced by the weak coordination between the carbonyl group and ruthenium complex. This highly efficient and practical reaction has a broad range of substrate scope with excellent functional-group tolerance. The tandem reaction provides a wide range of polycyclic products that have an indozilidine structural motif, and are found to potentially be synthetically and pharmaceutically valuable.