Approaches to 2-substituted chroman-4-ones: synthesis of (−)-pinostrobin

Cascade Oxidative Trifluoromethylthiolation and Cyclization of 3-Alkyl-1-(2-(alkynyl)phenyl)indoles

Persulfate-promoted radical cascade trifluoromethylthiolation and cyclization of 3-alkyl-1-(2-(alkynyl)phenyl)indoles with AgSCF₃ were investigated. This protocol provides a novel route to CF₃S-substituted indolo[1,2-a]quinoline-7-carbaldehydes and CF₃S-substituted indolo[1,2-a]quinoline-7-methanone derivatives via the formation of the C-SCF₃ bond and C-C bond and benzylic carbon oxidation in a single step. This reaction can accommodate a broad range of functional groups. The single-crystal X-ray diffraction data confirm the chemical structure of the product. A scale-up experiment and radical inhibition experiments were operated in the reaction system. Photophysical properties of some selected 5-((trifluoromethyl)thio)indolo[1,2-a]quinoline-7-carbaldehydes were studied by UV-visible and fluorescence spectroscopy.

Catalytic enantioselective synthesis of tetrasubstituted chromanones via palladium-catalyzed asymmetric conjugate arylation using chiral pyridine-dihydroisoquinoline ligands

Highly enantioselective conjugate addition reactions of arylboronic acids to 2-substituted chromones catalyzed by palladium complexes with new chiral Pyridine-Dihydroisoquinoline (PyDHIQ) ligands have been developed. These reactions provide highly enantioselective access to chromanones containing tetrasubstituted stereocenters. Various arylboronic acids and 2-substituted chromones can be used in the catalytic reaction to afford the chiral tetrasubstituted chromanones in good yields and excellent enantioselectivities (25 examples, up to 98% yields, up to 99% ee).

A review on biological sources, chemistry and pharmacological activities of pinostrobin

Pinostrobin, a dietary bioflavonoid discovered more than 6 decades ago in the heart-wood of pine (Pinus strobus), has depicted many pharmacological activities including anti-viral, anti-oxidant, anti-leukaemic, anti-inflammatory and anti-aromatase activities. It is an inhibitor of sodium channel and Ca(2+) signalling pathways and also inhibits intestinal smooth muscle contractions. In spite of the fact that pinostrobin has an application as functional foods, till-to-date no comprehensive review on pinostrobin has been carried out. Hence, the present review deals with the biological sources, chemistry and pharmacological activities of pinostrobin.

An eco-friendly enantioselective access to (R)-naringenin as inhibitor of proinflammatory cytokine release

(RS)-Naringenin is a flavanone well-known for its beneficial health-related properties, such as its anti-inflammatory activity. The preparative enantioselective chromatographic resolution of commercial (RS)-naringenin was performed on a Chiralpak AD-H column (500×50 mm i.d., dp 20 μm) using MeOH as eluent. The developed method is in accordance with the principles of green chemistry, since the environmental impact was lowered by recycling of the eluent, and allowed the production of gram amounts of each enantiomer with high purity (chemical purity >99%, enantiomeric excess (ee) >94%). Racemic and enantiomeric naringenin were subjected to an exhaustive in vitro investigation of anti-inflammatory activity, aimed at evaluating the relevance of chirality. The assay with cultured human peripheral blood mononuclear cells (hPBMC) activated by phytohemagglutinin A revealed that (R)-naringenin was more effective in inhibiting T-cell proliferation than the (S)-enantiomer and the racemate. Moreover, (R)-naringenin significantly reduced proinflammatory cytokine levels such as those of TNF-α and, with less potency, IL-6. These results evidenced the anti-inflammatory potential of naringenin and the higher capacity of (R)-naringenin to inhibit both in vitro hPBMC proliferation and cytokine secretion at non toxic doses. Thus, (R)-naringenin is a promising candidate for in vivo investigation.

Asymmetric Methods for the Synthesis of Flavanones, Chromanones, and Azaflavanones

Flavanones, chromanones, and related structures are privileged natural products that display a wide variety of biological activities. Although flavanoids are abundant in nature, there are a limited number of available general and efficient synthetic methods for accessing molecules of this class in a stereoselective manner. Their structurally simple architectures belie the difficulties involved in installation and maintenance of the stereogenic configuration at the C2 position, which can be sensitive and can undergo epimerization under mildly acidic, basic, and thermal reaction conditions. This review presents the methods currently used to access these related structures. The synthetic methods include manipulation of the flavone/flavanone core, carbon-carbon bond formation, and carbon-heteroatom bond formation.

The methanolic extract of Boesenbergia rotunda (L.) Mansf. and its major compound pinostrobin induces anti-ulcerogenic property in vivo: possible involvement of indirect antioxidant action

ETHNOPHARMACOLOGICAL RELEVANCE

Boesenbergia rotunda (L) Mansf. has been used for the treatment of gastrointestinal disorders including peptic ulcer. In the current study we aimed to investiagte the anti-ulcer activities of methanolic extract of B. rotunda (MEBR) and its main active compound, pinostrobin on ethanol-induced ulcer in rats. The possible involevement of lipid peroxidation, nitric oxide, cyclooxygenases and free radical scavenging mechanisms also has been investigated.

MATERIALS AND METHODS

Pinostrobin was isolated form the rhizomes of B. rotunda. Ulcer index, gastric juice acidity, mucus content, gross and histological gastric lesions and thiobarbituric acid reactive substances (TBARS) were evaluated in ethanol-induced ulcer in vivo. The effect of pinostrobin into lipopolysaccharide/interferon-γ stimulated rodent cells, COX-1 and COX-2 activities were done in vitro.

RESULTS

Pre-treatment with MEBR, pinostrobin or omeprazole protected the gastric mucosa as seen by reduction in ulcer area and mucosal content, reduced or absence of submucosal edema and leucocytes infiltration. Pinostrobin significantly (p<0.05) lowered the elevated TBARS level into gasteric homogenate. Pinostrobin did not produced significant in vitro inhibition of NO from LPS/IFN-γ activated rodent cells without affecting the viability of these cells. Further, the compound did bot revleaed inhibitory effects on both COX- 1& 2 enzymes. The antioxidant assays also exhibited non significance in vitro.

CONCLUSION

Thus it can be concluded that MEBR possesses anti-ulcer activity, which could be attributed to indirect anti-oxidant mechanism of pinostrobin but not to the intervention with nitric oxide and COX inflammation pathways.

Validation of the Ethnopharmacological Use of Polygonum Persicaria for its Antifungal Properties

Polygonum L. genus (Polygonaceae) is represented in Argentina by 21 species and some of them have been used in the traditional medicine of our country to treat affections related with fungal infections, such as skin ailments and vaginal diseases. With the aim of contributing to the correct ethnopharmacological use of this genus, in the present work we describe the antifungal properties of P. persicaria (species not studied up to now) and the bio-guided isolation of the main active compounds. Results showed that dichloromethane extracts was the most active with MICs (Minimun Inhibitory Concentrations) between 31.2 – 1000 μg/mL, validating the ethnopharmacological use of P. persicaria to treat affections related with fungal infections in the Argentinean traditional medicine.

Highly enantioselective and efficient synthesis of flavanones including pinostrobin through the rhodium-catalyzed asymmetric 1,4-addition

An efficient synthesis of bioactive chiral flavanones (1) was achieved through the Rh-catalyzed asymmetric 1,4-addition of arylboronic acid to chromone. The reaction in toluene proceeded smoothly at room temperature in the presence of 0.5% Rh catalyst with electron-poor chiral diphosphine MeO-F(12)-BIPHEP. In this reaction, the 1,2-addition to (S)-1 frequently occurred to yield (2S,4R)-2,4-diaryl-4-chromanol as a byproduct, which could be reduced by changing the reaction solvent to CH(2)Cl(2) to deactivate the Rh catalyst (3% required).

The Use of Chiral BINAM NHC-Rh(III) Complexes in Enantioselective Hydrosilylation of 3-Oxo-3-arylpropionic Acid Methyl or Ethyl Esters

Axially chiral BINAM N-heterocyclic carbene (NHC)-Rh(III) complexes were applied in the enantioselective hydrosilylation of 3-oxo-3-arylpropionic acid methyl or ethyl esters. The reduction products 3-hydroxy-3-arylpropionic acid methyl or ethyl esters could be obtained in good yields with good to excellent enantioselectivities under mild conditions.

Benzylic oxidation catalyzed by dirhodium(II,III) caprolactamate

[reaction: see text] Dirhodium caprolactamate [Rh2(cap)4] is an effective catalyst for benzylic oxidation with tert-butyl hydroperoxide (TBHP) under mild conditions. Sodium bicarbonate is the optimal base additive for substrate conversion. Benzylic carbonyl compounds are readily obtained, and a formal synthesis of palmarumycin CP2 using this methodology is described.

Antiplasmodial constituents of Cajanus cajan

Bioactivity-guided fractionation of extracts of roots and leaves of Cajanus cajan afforded 8 compounds: betulinic acid, biochanin A, cajanol, genistein and 2'-hydroxygenistein, longistylin A and C, and pinostrobin. The two stilbenes, longistylin A and C, and betulinic acid showed a moderately high in vitro activity against the chloroquine-sensitive Plasmodium falciparum strain 3D7.

Activity-guided isolation of the chemical constituents of Muntingia calabura using a quinone reductase induction assay

Activity-guided fractionation of an EtOAc-soluble extract of the leaves of Muntingia calabura collected in Peru, using an in vitro quinone reductase induction assay with cultured Hepa 1c1c7 (mouse hepatoma) cells, resulted in the isolation of a flavanone with an unsubstituted B-ring, (2R,3R)-7-methoxy-3,5,8-trihydroxyflavanone (5), as well as 24 known compounds, which were mainly flavanones and flavones. The structure including absolute stereochemistry of compound 5 was determined by spectroscopic (HRMS, 1D and 2D NMR, and CD spectra) methods. Of the isolates obtained, in addition to 5, (2S)-5-hydroxy-7-methoxyflavanone, 2',4'-dihydroxychalcone, 4,2',4'-trihydroxychalcone, 7-hydroxyisoflavone and 7,3',4'-trimethoxyisoflavone were found to induce quinone reductase activity.