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Highly diastereo and enantioselective [4+2] cycloadditions have been achieved between pyrrolidone-derived cyclic enones and α-haloaldehydes under mild conditions. Relying on extremely reactive in-situ generated chiral N-heterocyclic carbenes, this stereoselective annulation proceeds efficiently even on the gram scale with the catalyst loading as low as 0.025 mol% (250 ppm). A variety of cis-substituted bicyclic dihydropyranones can be produced in up to 96% yield with up to ＞99% ee. In addition, simple, inexpensive linear aldehydes such as n-propanal can be used directly in asymmetric cycloadditions via oxidative N-heterocyclic carbene organocatalysis with low catalyst loading. This method may provide an economical and practical approach for the asymmetric synthesis of medicinally relevant molecules. [ABSTRACT FROM AUTHOR]

In using nanomaterials for advanced photodynamic therapy, it is important to improve surface modification to increase stability, minimize non-specific loss of drugs in blood circulation, enhance the photostability of photosensitizers, and achieve highly efficient intracellular uptake. In this report, we for the first time covalently conjugate photosensitizer Chlorin e6 (Ce6) to polyethylene glycol modified layered double hydroxides and produce hybrid nanoflakes. These nanoflakes display many superior characteristics and lead to excellent in vivo photodynamic therapeutic efficiency and safety profiles. [ABSTRACT FROM AUTHOR]

A highly enantioselective organocatalytic inverse-electron-demand oxo-Diels–Alder reaction involving aqueous acetaldehyde has been discovered. The reaction, in which cyclic enones serve as dienes in the presence of readily available secondary amine catalysts, allows facile construction of optically active bicyclic dihydropyrans. Other typical enolizable aliphatic aldehydes can also serve as competent dienophiles in the reaction. [ABSTRACT FROM AUTHOR]