Gold-Catalyzed Synthesis of Icetexane Cores: Short Synthesis of Taxamairin B and Rosmaridiphenol.

We report the short synthesis of two natural products, rosmaridiphenol and taxamairin B, from key intermediates and , which were prepared from enynals and , respectively, by using a gold-catalyzed cyclization reaction. This approach can be widely applied in the synthesis of [6,7,6]-fused tricyclic compounds found in many icetexane diterpenoids.

Production of bio-oil from fast pyrolysis of biomass using a pilot-scale circulating fluidized bed reactor and its characterization.

To circumvent the adverse impacts arising from an excessive use of fossil fuels, bioenergy and chemical production from a carbon neutral resource (biomass) has drawn considerable attention over the last two decades. Among various technical candidates, fast pyrolysis of biomass has been considered as one of the viable technical routes for converting a carbonaceous material (biomass) into biocrude (bio-oil). In these respects, three biomass samples (i.

Copper-catalyzed tandem reaction of 2-alkynylanilines with benzoquinones: efficient access to 3-indolylquinones.

A simple, mild, catalytic and efficient method for the straightforward synthesis of an interesting class of 2-aryl/alkyl-substituted-3-indolyl quinones in good to high yields is reported for the first time. This atom-efficient method proceeds copper-catalyzed one-pot sequential intramolecular hydroamination (C-N bond formation) of 2-alkynylanilines followed by oxidative C-C coupling with benzoquinones.

A DNA immunoprecipitation assay used in quantitative detection of in vitro DNA-protein complex binding.

To begin gene transcription, several transcription factors must bind to specific DNA sequences to form a complex via DNA-protein interactions. We established an in vitro method for specific and sensitive analyses of DNA-protein interactions based on a DNA immunoprecipitation (DIP) method. We verified the accuracy and efficiency of the DIP assay in quantitatively measuring DNA-protein binding using transcription factor CP2c as a model.

1,3-Dipolar cycloaddition of 4-platinumisochromenyliums with an olefin and tandem insertion into benzylic C-H bonds.

Isochromenylium-4-ylplatinum(II) species, generated from 1-(2-alkynylphenyl)hex-5-en-1-ones and Pt(II), reacted with a pendant olefin via [3+2] cycloaddition to form tetracyclic Pt-carbene complexes, which underwent C-H insertion with a benzyloxy group at δ or ε positions to give highly complex polycycles, which are otherwise hard to access.

Heat processing decreases Amadori products and increases total phenolic content and antioxidant activity of Korean red ginseng.

The functional properties of Korean red ginseng (KRG) are known to be dependent upon the extent of heat processing. We demonstrated that repeated heat processing in the preparation of KRG decreased its arginyl-fructosyl-glucose (AFG) content and metal chelating capacity. On the other hand, the total phenolic compound content, in vitro peroxyl radical scavenging ability, and cellular peroxyl and hydroxyl radical scavenging ability increased with repeated heat processing.

Stereocontrolled synthesis of oxygen-bridged polycycles via intermolecular [3+2] cyclization of platinum-bound pyrylium with alkenes.

2-(3-Benzyloxy)prop-1-ynyl)benzaldehyde with PtCl(2) in toluene would form Pt-pyryliums that underwent [3+2] cycloaddition with alkenes to the oxygen-bridged (5H-benzo[7]annulen-5-ylidene)platinum(ii) intermediates with good stereoselectivities. Their tandem rearrangement afforded diverse types of polycycles depending on the electronic nature of the alkenes.

Pt-catalyzed hydrative cyclization of 2-enynylbenzaldehydes and its application to faveline synthesis.

Various 2-[6-en-1-ynyl]benzaldehydes and their analogues were successfully cyclized via Huisgen-type [3+2] cycloaddition to the tetracyclic platinum-carbene complex, which would subsequently undergo hydration to afford the tricyclic products in good yields with excellent stereoselectivities. This hydrative cyclization was also applied to the faveline synthesis.

Domino process in silver-catalyzed reactions of N-arylformimidates and active methylene compounds involving cycloisomerization and 1,3-alkenyl shift.

We have developed an efficient method for the synthesis of 2,3-disubstituted indoles from alkyne iminoethers 1 that employs a domino process involving Ag-catalyzed condensation followed by a tandem Ag-induced cycloisomerization and 1,3-alkenyl shift to Ag-activated carbon. This methodology can be useful in regioselectively constructing 3-alkylated indoles, which are part of the structures of biologically active compounds and important alkaloids.

Au(I)-catalyzed hydrative rearrangement of 1,1-diethynylcarbinol acetates to functionalized cyclopentenones and allenones.

Atom-economical syntheses of isomeric 5-acetoxy-2-alkyl-2-cyclopentenones (2) and acetoxymethyl alpha-alkylallenones (3) have been described via Au-catalyzed hydrative rearrangement of 1,1-diethynylcarbinol acetates (1). In anhydrous condition, Au(I)-catalyzed [3,3]-rearrangement of 1 afforded the 3-alkynylallenyl acetate 4 in low yield. Treatment of 1 with Au(I) catalyst in wet CH(2)Cl(2) produced either 2 or 3 as a major product depending on the temperature, reaction time, and catalyst loading.

Regioselectivities in alkyne activation: synthesis of 2-(bicyclo[3.1.0]hexan-1-yl)furan derivatives by Au-catalyzed cyclization and cyclopropanation.

2-Alkynyl-1-cycloalkenecarbaldehydes, in the presence of gold catalysts, undergo aurative cyclization via the 5-exo-dig mode to form Au-carbene intermediates which react with a double bond to form the corresponding cyclopropanes.

Highly functionalized and stereocontrolled syntheses of 2-(2-methylenecycloalkyl)-furan derivatives by Pd-catalyzed cycloreduction.

[structure: see text]. We have discovered a new method employing Pd-catalyzed cycloreduction of conjugated enynals 1 bearing an alkyne unit leading to the corresponding 2-(2-methylenecycloalkyl)-furans 2a-j and a related compound 7 in good to excellent yields.

Highly efficient [2 + 2] intramolecular cyclizations of allenynes under microwave irradiation: construction of fused bicyclic compounds.

A palladium [2 + 2] cycloaddition of 1,6- and 1,7-allenyne carboxylates and microwave-mediated [2 + 2] cycloaddition of various 1,n-allenynes were developed and, particularly, the microwave irradiated [2 + 2] cycloaddition of allenynes can provide a simple, general and eco-friendly synthetic method to fused bicyclo[m,2,0]alkadienes.

Gold-catalyzed cycloisomerization of o-alkynylbenzaldehydes with a pendant unsaturated bond: [3 + 2] cycloaddition of gold-bound 1,3-dipolar species with dipolarophiles.

[reaction: see text] A new and novel Au-catalyzed cycloisomerization of ynals bearing a pendant unsaturated bond leading to synthetically valuable [6.7.n]-tricyclic compounds were developed.

Enantiomeric 1,2,4-trioxanes display equivalent in vitro antimalarial activity versus Plasmodium falciparum malaria parasites: implications for the molecular mechanism of action of the artemisinins.

The aim of this study was to synthesise pure enantiomers of potent antimalarial 1,2,4-trioxanes, which are related to the natural antimalarial artemisinin, and then to assay each against a panel of Plasmodium falciparum strains. The working hypothesis was that if the artemisinin derivatives interact with a specific protein-target site, then there should be stereoselective differences in their activity. In five different P.

Rhodium-catalyzed tandem cyclization-cycloaddition reactions of enynebenzaldehydes: construction of polycyclic ring systems.

o-(1,6-Enynyl)benzaldehydes underwent a novel mode of cycloaddition using Rh(I)-precatalyst, via[3+2] cycloaddition of presumed dipolar carbonyl ylide intermediate generated by Rh-catalyst and the utility of this mechanistically intriguing enyne cyclization can be found in a number of polycyclic natural product skeletons.

On the regioselectivity of Pd-catalyzed additions of organoboronic acids to unsymmetrical alkynes.

The Pd-catalyzed reaction of unsymmetrical alkynes with organoboronic acids gave a mixture of products and, whose ratios were controlled by the electronic as well as steric effects of the substrates.

Palladium-catalyzed addition of organoboronic acids to allenes.

The palladium-catalyzed addition reaction of alkenyl- or aryl-boronic acids into various allenes is described, which allows C-C bond formation in a highly regioselective manner under very mild conditions.

Palladium-catalyzed cycloalkylations of 2-bromo-1,n-dienes with organoboronic acids.

Cascade palladium-catalyzed cycloalkylations of 2-bromo-1,n-dienes were accomplished in good to excellent yields, where the alkylpalladium intermediates, formed via an intramolecular Heck reaction of 2-bromo-1,n-dienes (n = 6 or 7), were successfully cross-coupled with various organoboronic acids. The optimal yields were achieved by the use of cesium carbonate in ethanol with Pd(PPh(3))(4) as catalyst, with 2-bromo-1,n-dienes and organoboronic acids at concentrations of 0.2 and 0.

Decarbopalladation of pi-allylpalladium intermediates formed from palladium-catalyzed arylations of 3-allen-1-ols.

[reaction: see text] Unusual palladium-catalyzed arylative fragmentations of acyclic 3-allen-1-ols were observed. Oxidative addition of Pd(0) to aryl halides would form the arylpalladium halides, which added to the central carbon of allenes via carbopalladation to form the pi-allylpalladium intermediates. The pi-allylpalladium intermediates would be reductively eliminated via carbon-carbon cleavage to give the arylated dienes and the alpha-hydroxyalkylpalladium intermediates, which were further reductively eliminated to the corresponding aldehydes.