Application of quercetin flavonoid based hybrid nanocomposites: A review.

Natural bioflavonoids are an essential component of dietary supplements possessing antimicrobial properties. Many of the bioflavonoids have resulted in positive antitumor, anticancer, antibacterial, antifungal, anti-inflammatory properties, but the efficacy remains low due to toxicity at the molecular level whereas antiviral property limits to negative. The synergistic link between nanoscience and flavonoid chemistry enhances the epidemiological properties of flavonoid and also diminish the antimicrobial resistivity (AMR) by forming their hybrid nanocomposites.

Cinchonamine Squaramide Catalyzed Asymmetric aza-Michael Reaction: Dihydroisoquinolines and Tetrahydropyridines.

The first example of a chiral cinchona-squaramide catalyzed enantioselective intramolecular aza-Michael addition for the synthesis of dihydroisoquinolines and tetrahydropyridines has been developed. In general, good yields and excellent enantioselctivities were observed. Broad classes of Michael acceptors, such as enones, esters, thioesters, and Weinreb amides, were successful substrates.

Catalytic Asymmetric Conjugate Addition of Carboxylic Acids via Oxa-Michael Reaction of Peroxy Hemiacetals followed by Kornblum DeLaMare Fragmentation.

Disclosed herein an overall methodology constitutes an equivalent to the long sought after enantioselective intramolecular oxa-Michael (IOM) reaction of carboxylic acids. An organocatalyzed IOM reaction of in situ formed peroxy hemiacetals followed by a Kornblum DeLaMare type rearrangement cascade provides a broad class of chiral lactones in good yields and with excellent enatioselectvities. Remarkably, the pure chiral lactones are obtained without any silica gel column chromatography, and in many cases, the enantioselectivity is further increased by a simple hexane wash of the isolated solid products.

Organocatalytic Enantioselective Intramolecular Oxa-Michael Reaction of Enols: Synthesis of Chiral Isochromenes.

An unprecedented enantioselective intramolecular oxa-Michael reaction of enols has been described. A squaramide-containing tertiary amine based bifunctional organocatalyst efficiently activates the o-homoformyl chalcones to provide the chiral isochromenes in moderate yields and good to excellent enantioselectivities. Further, late-stage functionalizations of the vinyl ether moiety of the chiral isochromene products have also been exemplified.

Enantio- and Diastereoselective Synthesis of exo-Peroxyacetals: An Organocatalyzed Peroxyhemiacetalization/oxa-Michael Addition Cascade.

An unprecedented enantioselective peroxyhemiacetalization/oxa-Michael addition cascade of ortho-formyl homochalcones has been developed using cinchona-alkaloid-based chiral bifunctional organocatalysts to provide cis-configured exo-peroxyacetals, a new class of organic peroxide, in good yields with excellent enantio- and diastereoselectivities. The resulting cis-configured exo-peroxyacetals were converted into the corresponding trans-configured peroxyacetals without affecting the enantioselectivity. Furthermore, the displacement of the peroxide moiety of exo-peroxyacetals with various nucleophiles has been demonstrated to afford 1,3-disubstituted isochromans with high diastereoselectivities and excellent enantioselectivities.