A Scaleable Synthesis of Fiduxosin

Tunable Zinc-Mediated Reductive Cyclization of Diastereomeric 3-Nitro-4-phenacyl-2-(trihalomethyl)chromanes to Fused Pyrroline N-Oxides, Pyrrolines, and Pyrrolidines

Reductive cyclization of trans,trans- and trans,cis-isomers of the 2-CF3-substituted 3-nitro-4-phenacylchromanes with Zn-based reductive systems, depending on the conditions, affords 4-CF3-substituted 1,3a,4,9b-tetrahydrochromeno[3,4-b]pyrrole 3-oxides, 1,3a,4,9b-tetrahydrochromeno[3,4-b]pyrroles, or 1,2,3,3a,4,9b-hexahydrochromeno[3,4-b]pyrroles in good yields without changing the relative configuration of the pyran ring. A similar process involving the 2-CCl3-substituted 3-nitro-4-phenacylchromanes is accompanied by reductive dehalogenation to form the corresponding 4-dichloromethyl-substituted fused chromanes along with the 3-(2-hydroxyaryl)-2-(2,2-dichlorovinyl)-5-phenyl-2H-pyrroline 1-oxides as pyran ring opening products. The structure and relative configuration of the obtained products was reliably confirmed by X-ray diffraction analysis and 2D NMR spectroscopy.

Exploring structural effects in a new class of NRF2 inhibitors

NRF2 is a transcription factor that controls the cellular response to various stressors, such as reactive oxygen and nitrogen species. As such, it plays a key role in the suppression of carcinogenesis, but constitutive NRF2 expression in cancer cells leads to resistance to chemotherapeutics and promotes metastasis. As a result, inhibition of the NRF2 pathway is a target for new drugs, especially for use in conjunction with established chemotherapeutic agents like carboplatin and 5-fluorouracil. A new class of NRF2 inhibitors has been discovered with substituted nicotinonitriles, such as MSU38225. In this work, the effects on NRF2 inhibition with structural changes were explored. Through these studies, we identified a few compounds with as good or better activity than the initial hit but with greatly improved solubility. The syntheses involved a variety of metal-catalyzed reactions, including titanium multicomponent coupling reactions and various Pd and Cu coupling reactions. In addition to inhibiting NRF2 activity, these new compounds inhibited the proliferation and migration of lung cancer cells in which the NRF2 pathway is constitutively activated.

Copper-Catalyzed Asymmetric Diyne Cyclization via [1,2]-Stevens-Type Rearrangement for the Synthesis of Chiral Chromeno[3,4-c]pyrroles

Here, we report a copper-catalyzed asymmetric cascade cyclization/[1,2]-Stevens-type rearrangement via a non-diazo approach, leading to the practical and atom-economic assembly of various valuable chiral chromeno[3,4-c]pyrroles bearing a quaternary carbon stereocenter in generally moderate to good yields with wide substrate scope and excellent enantioselectivities (up to 99 % ee). Importantly, this protocol not only represents the first example of catalytic asymmetric [1,2]-Stevens-type rearrangement based on alkynes but also constitutes the first asymmetric formal carbene insertion into the Si-O bond.

Synthesis and Structure-Activity Relationship Studies of Hydrazide-Hydrazones as Inhibitors of Laccase from Trametes versicolor

A series of hydrazide-hydrazones 1-3, the imine derivatives of hydrazides and aldehydes bearing benzene rings, were screened as inhibitors of laccase from Trametes versicolor. Laccase is a copper-containing enzyme which inhibition might prevent or reduce the activity of the plant pathogens that produce it in various biochemical processes. The kinetic and molecular modeling studies were performed and for selected compounds, the docking results were discussed. Seven 4-hydroxybenzhydrazide (4-HBAH) derivatives exhibited micromolar activity Ki = 24-674 µM with the predicted and desirable competitive type of inhibition. The structure-activity relationship (SAR) analysis revealed that a slim salicylic aldehyde framework had a pivotal role in stabilization of the molecules near the substrate docking site. Furthermore, the presence of phenyl and bulky tert-butyl substituents in position 3 in salicylic aldehyde fragment favored strong interaction with the substrate-binding pocket in laccase. Both 3- and 4-HBAH derivatives containing larger 3-tert-butyl-5-methyl- or 3,5-di-tert-butyl-2-hydroxy-benzylidene unit, did not bind to the active site of laccase and, interestingly, acted as non-competitive (Ki = 32.0 µM) or uncompetitive (Ki = 17.9 µM) inhibitors, respectively. From the easily available laccase inhibitors only sodium azide, harmful to environment and non-specific, was over 6 times more active than the above compounds.

Selective construction of functionalized chromeno[3,4-b]pyrroles and benzo[c]chromenesviaa K3PO4promoted three-component reaction

A K₃PO₄promoted three-component reaction of pivaloylacetonitrile (benzoylacetonitrile), dialkyl but-2-ynedioates and 2-aryl-3-nitrochromenes afforded functionalized chromeno[3,4-b]pyrroles.

Domino Transformations of Ene/Yne Tethered Salicylaldehyde Derivatives: Pluripotent Platforms for the Construction of High sp3 Content and Privileged Architectures

Diversity-oriented synthesis (DOS) has become a powerful synthetic tool that facilitates the construction of nature-inspired and privileged chemical space, particularly for sp³ -rich non-flat scaffolds, which are needed for phenotypic screening campaigns. These diverse compound collections led to the discovery of novel chemotypes that can modulate the protein function in underrepresented biological space. In this context, starting material-driven DOS is one of the most important tools used to build diverse compound libraries with rich stereochemical and scaffold diversity. To this end, ene/yne tethered salicylaldehyde derivatives have emerged as a pluripotent chemical platform, the products of which led to the construction of a privileged chemical space with significant biological activities. In this review, various domino transformations employing o-alkene/alkyne tethered aryl aldehyde/ketone platforms are described and discussed, with emphasis on the period from 2011 to date.

A regio- and stereocontrolled approach to the synthesis of 4-CF3-substituted spiro[chromeno[3,4-c]pyrrolidine-oxindoles]viareversible [3+2] cycloaddition of azomethine ylides generated from isatins and sarcosine to 3-nitro-2-(trifluoromethyl)-2H-chromenes

The first example of regio- and stereocontrolled synthesis of 4-CF₃-spiro[chromeno[3,4-c]pyrrolidine-oxindoles] with anticancer activity.

Disparate Effects of Stilbenoid Polyphenols on Hypertrophic Cardiomyocytes In Vitro vs. in the Spontaneously Hypertensive Heart Failure Rat

Stilbenoids are bioactive polyphenols, and resveratrol (trans-3,5,4′-trihydroxystilbene) is a representative stilbenoid that reportedly exerts cardioprotective actions. As resveratrol exhibits low oral bioavailability, we turned our attention to other stilbenoid compounds with a history of medicinal use and/or improved bioavailability. We determined the effects of gnetol (trans-3,5,2′,6′-tetrahydroxystilbene) and pterostilbene (trans-3,5-dimethoxy-4′-hydroxystilbene) on cardiac hypertrophy. In vitro, gnetol and pterostilbene prevented endothelin-1-induced indicators of cardiomyocyte hypertrophy including cell enlargement and protein synthesis. Gnetol and pterostilbene stimulated AMP-activated protein kinase (AMPK), and inhibition of AMPK, using compound C or shRNA knockdown, abolished these anti-hypertrophic effects. In contrast, resveratrol, gnetol, nor pterostilbene reduced blood pressure or hypertrophy in the spontaneously hypertensive heart failure (SHHF) rat. In fact, AMPK levels were similar between Sprague-Dawley and SHHF rats whether treated by stilbenoids or not. These data suggest that the anti-hypertrophic actions of resveratrol (and other stilbenoids?) do not extend to the SHHF rat, which models heart failure superimposed on hypertension. Notably, SHHF rat hearts exhibited prolonged isovolumic relaxation time (an indicator of diastolic dysfunction), and this was improved by stilbenoid treatment. In conclusion, stilbenoid-based treatment as a viable strategy to prevent pathological cardiac hypertrophy, a major risk factor for heart failure, may be context-dependent and requires further study.

Diastereoselective synthesis of benzo[d]chromeno[3′,4′:3,4]pyrrolo[2,1-b]thiazoles via cycloaddition reaction of benzothiazolium salts with 3-nitrochromenes

Diastereospecific synthesis of benzo[d]chromeno[3′,4′:3,4]pyrrolo[2,1-b]thiazoles via cycloaddition reaction of benzothiazolium salts with 3-nitrochromenes.

Old tricks, new dogs: organocatalytic dienamine activation of α,β-unsaturated aldehydes

Chiral secondary amines are some of the most commonly used kinds of catalysts. They have become a reliable tool for the α- and β-activation of carbonyl compounds, via HOMO, SOMO or LUMO activation pathways. Recently, chemists have turned their attention to the development of novel organocatalytic strategies for remote functionalisation, targeting stereocentres even more distant from the catalyst-activation site, through dienamine, trienamine, and vinylogous iminium ion pathways (γ-, ε- and δ-positions, respectively). Here we outline and discuss the state-of-the-art in dienamine activation, classifying examples according to the different reactive activation pathways followed by the formed dienamine intermediate (1,3-, 1,5-, 2,5- and 4,5-functionalisation) and the reaction type developed, as determined by the structure and the nature of electrophiles and nucleophiles.

Diastereoselective Cascade Assembly of Functionalized Pyrano[3,4-c]pyrrole Derivatives

A novel convenient approach for the synthesis of densely functionalized pyrano[3,4-c]pyrrole derivatives was developed. Cascade transformation of the simple adducts of tetracyanoethylene (TCNE) and ketones (4-oxoalkane-1,1,2,2-tetracarbonitriles) in the presence of aldehyde under the action of acetic acid led to the diastereoselective formation of targeted pyrano[3,4-c]pyrroles. The reaction pathway was thoroughly investigated, and proposed intermediates were shown to be consistent with experiment.

Biology-oriented synthesis of benzopyrano[3,4-c]pyrrolidines

A natural product inspired synthesis of 6,6,5-tricyclic compounds via a silver(I)-catalyzed formal 1,3-dipolar cycloaddition of coumarins with α-iminoesters was developed. The reaction proceeds in a stepwise reaction course under formation of the trans-substituted diastereomer with respect to the 1,3-dipole and shows a broad substrate scope.

Rational design and synthesis of novel 2-(substituted-2H-chromen-3-yl)-5-aryl-1H-imidazole derivatives as an anti-angiogenesis and anti-cancer agent

Based on the earlier proven pharmacophore analogues of cancer a novel 2-(substituted-2H-chromen-3-yl)-5-aryl-1H-imidazoles were rationally designed, synthesized and used for competitive biological activity against cancer cell lines.

Palladium-catalyzed substitution of (coumarinyl)methyl acetates with C-, N-, and S-nucleophiles

The palladium-catalyzed nucleophilic substitution of (coumarinyl)methyl acetates is described. The reaction proceeds though a palladium π-benzyl-like complex and allows for many different types of C-, N-, and S-nucleophiles to be regioselectively added to the biologically active coumarin motif. This new method was utilized to prepare a 128-membered library of aminated coumarins for biological screening.

Diastereocontrolled Synthesis of Enantioenriched 3,4-Disubstituted β-Prolines

Enantioenriched 3,4-disubstituted beta-prolines have been prepared with a high diastereocontrol through a carbometalation reaction or through a domino Michael addition/carbometalation reaction.