The details of all steps involved in the quantification of
biofilm formation in microtiter plates are described. The
presented protocol incorporates information on assessment of
biofilm production by staphylococci, gained both by direct
experience as well as by analysis of methods for assaying
biofilm production. The obtained results should simplify
quantification of biofilm formation in microtiter plates, and
make it more reliable and comparable among different
laboratories.

Quantification of biofilm in microtiter plates: overview oftesting conditions and practical recommendations for assessmentof biofilm production by staphylococci.

Many fungi, lichens, and bacteria produce xanthones (derivatives of 9H-xanthen-9-one, “xanthone” from the Greek “xanthos”, for “yellow”) as secondary metabolites. Xanthones are typically polysubstituted and occur as either fully aromatized, dihydro-, tetrahydro-, or, more rarely, hexahydro-derivatives. This family of compounds appeals to medicinal chemists because of their pronounced biological activity within a notably broad spectrum of disease states, a result of their interaction with a correspondingly diverse range of target biomolecules. This has led to the description of xanthones as “privileged structures”.(1) Historically, the total synthesis of the natural products has mostly been limited to fully aromatized targets. Syntheses of the more challenging partially saturated xanthones have less frequently been reported, although the development in recent times of novel and reliable methods for the construction of the (polysubstituted) unsaturated xanthone core holds promise for future endeavors. In particular, the fascinating structural and biological properties of xanthone dimers and heterodimers may excite the synthetic or natural product chemist.

Xanthones from fungi, lichens, and bacteria : the natural products and their synthesis

Recent advances in asymmetric catalysis with cinchona alkaloid-based primary amines

Recent advances in the organocatalytic enantioselective synthesis of γ-nitrocarbonyl compounds through Michael additions of either nitroalkanes to α,β-unsaturated carbonyl derivatives or enolizable carbonyl compounds to nitroalkenes are surveyed. Domino processes leading to structurally more complex products bearing the γ-nitrocarbonyl functionality are also reviewed.

Asymmetric organocatalytic synthesis of γ-nitrocarbonyl compounds through Michael and Domino reactions

A series of novel helical poly(phenylacetylene)s bearing amino-functionalized cinchona alkaloid pendant groups connecting to the phenyl rings through an amide linkage were prepared by the polymerization of the corresponding phenylacetylenes using a rhodium catalyst. All of the polymers formed a preferred-handed helical conformation biased by the optically active pendants, resulting in the induced circular dichroism in their π-conjugated polymer backbone regions. The optically active helical polymers efficiently catalyzed the asymmetric Henry reaction of benzaldehydes with nitromethane, giving optically active products up to 94% enantiomeric excess (ee) when the poly(phenylacetylene) bearing an amino-functionalized quinine pendant group was used as the polymeric organocatalyst; the enantioselectivity was remarkably higher than those catalyzed by the corresponding nonhelical poly(phenylacetylene) (18% ee) and the monomer (28% ee).

Remarkable Enhancement of the Enantioselectivity of an Organocatalyzed Asymmetric Henry Reaction Assisted by Helical Poly(phenylacetylene)s Bearing Cinchona Alkaloid Pendants via an Amide Linkage

Chemistry of the fumiquinazolines and structurally related alkaloids

Highly Enantioselective 1,4-Michael Additions of Nucleophiles to Unsaturated Aryl Ketones with Organocatalysis by Bifunctional Cinchona Alkaloids

This work reviews the contributions of the corresponding author (M.M.M.P.) and her research group to Medicinal Chemistry concerning the isolation from plant and marine sources of xanthone derivatives as well as their synthesis, biological/pharmacological activities, formulation and analytical applications. Although her group activity has been spread over several chemical families with relevance in Medicinal Chemistry, the main focus of the investigation and research has been in the xanthone family. Xanthone derivatives have a variety of activities with great potential for therapeutic applications due to their versatile framework. The group has contributed with several libraries of xanthones derivatives, with a variety of activities such as antitumor, anticoagulant, antiplatelet, anti-inflammatory, antimalarial, antimicrobial, hepatoprotective, antioxidant, and multidrug resistance reversal effects. Besides therapeutic applications, our group has also developed xanthone derivatives with analytical applications as chiral selectors for liquid chromatography and for maritime application as antifouling agents for marine paints. Chemically, it has been challenging to afford green chemistry methods and achieve enantiomeric purity of chiral derivatives. In this review, the structures of the most significant compounds will be presented.

https://www.mdpi.com/1420-3049/26/2/431/pdf

From Natural Products to New Synthetic Small Molecules: A Journey through the World of Xanthones.

Xanthones are important O-heteroaromatic tricyclic molecules exhibiting a wide range of bioactivities and can represent a showcase to highlight the recent techniques and strategies in organic synthesis towards lead discovery and optimization. This review gives an insight into the recent literature disclosed to obtain the xanthone core, including the drug-like azaxanthones, isosteres of xanthones, by exploiting the optimization of well-known procedures as well as disruptive developed methodologies. With this review, it is expected to provide a useful chemical toolbox to synthetic medicinal chemistry focusing on these privileged structures, covering from 2012 to 2020, with some older examples of azaxanthones.

Diana I. S. P. Resende

Papers

Chemistry of the fumiquinazolines and structurally related alkaloids

Highly Enantioselective 1,4-Michael Additions of Nucleophiles to Unsaturated Aryl Ketones with Organocatalysis by Bifunctional Cinchona Alkaloids

From Natural Products to New Synthetic Small Molecules: A Journey through the World of Xanthones.

Recent advances in the synthesis of xanthones and azaxanthones

Xanthenes in Medicinal Chemistry - Synthetic strategies and biological activities.