Formal Synthesis of Amipurimycin and 4'-Deoxymiharamycin B by Way of Sequential Asymmetric Metal Catalysis.

Herein, we describe a highly efficient formal synthesis of nucleoside antibiotics amipurimycin and 4'-deoxymiharamycin B. A signature event is highlighted by the sequential metal catalysis combining (i) Pd-catalyzed asymmetric hydroalkoxylation of an alkoxyallene; (ii) Ru-catalyzed enyne-methathesis, and (iii) Os-catalyzed dihydroxylation. Remarkably, this atom-efficient sequence allows for the construction of a 3'-branched pyranose core structure in only four steps from readily available Garner's aldehyde.

Formal Synthesis of (+)-Sinefungin by Way of Sequential Asymmetric Metal Catalysis.

Here, we report a approach toward (+)-sinefungin, a potent inhibitor of the physiological methyl transfer process. A key feature is represented by the sequential metal catalysis combining Pd-catalyzed hydroalkoxylation and ring-rearrangement metathesis. The unique advantage of the method is highlighted by the unprecedented complete control of the C stereocenter.

Total Synthesis of the Purported Structure of Branched Resin Glycosides Merremoside G and H.

The first total synthesis of the purported structure of branched resin glycosides merremoside G and H is accomplished. A signature step is represented by the sequential transition-metal-catalyzed coupling of stable trisaccharide homoallylic alcohol and monosaccharide alkoxyallene to afford the pentasaccharide skeleton. This strategy is conducted under mild conditions with no need of preactivation.

Synthesis of the Tetrasaccharide Glycone Part of Tetrocarcin A.

A synthesis of the tetrasaccharide fragment of tetrocarcin A is described. The key feature of this approach is highlighted by the regio- and diastereoselective Pd-catalyzed hydroalkoxylation of ene-alkoxyallenes with an unprotected l-digitoxose glycoside. The subsequent reaction with digitoxal in combination with chemoselective hydrogenation generated the target molecule.

Pd-Catalyzed Umpolung Chemistry of Glycal Acetates and Their [2,3]-Dehydrosugar Isomers.

Glycals and their [2,3]-dehydrosugar derivatives have commonly been used in synthetic chemistry as electrophiles. Here we report a Pd-catalyzed polar inversion (umpolung) of this reaction, where the glycals and isomers can be used as nucleophiles. The reaction showed high regio- and stereoselectivity in the presence of numerous aromatic and aliphatic aldehydes.

Sequential Metal Catalysis towards 7-Oxostaurosporine and Its Non-Natural Septanose Analogue.

We report sequential metal catalysis towards indolocarbazole glycosides. The signature event is highlighted by i) Pd -catalyzed addition of indolocarbazole to alkoxyallene combined with ring-closing-metathesis; ii) Ru-catalyzed chemoselective olefin migration; iii) Pd -catalyzed oxidative cyclization to build the bicyclic core structure of the target compounds. This approach gave access to both natural pyranose- and non-natural septanose glycosides.

Generation of N-H Imines from α-Azidocarboxylic Acids through Ru-Catalyzed Decarboxylation.

A new method for the synthesis of N-H imines from α-azidocarboxylic acids was developed, which proceeds through decarboxylative C-C bond cleavage catalyzed by a commercial diruthenium complex ([CpRu(CO)]) under visible light irradiation at room temperature within several minutes. The reactive products undergo condensation, which forms cyclic trimers (2,4,6-trialkylhexahydro-1,3,5-triazines) or linear ,'bis(arylmethylidene)arylmethanediamines in quantitative yields. Alternatively, the N-H imines can be trapped with benzylamine and 2-(aminomethyl)aniline, providing stable -benylimines and tetrahydroquinazolines, respectively.

Synthetic Study toward Saccharomicin Based upon Asymmetric Metal Catalysis.

Here, we report a metal-catalyzed approach toward the stereoselective glycosidic bond formation in saccharomicin. The signature step is highlighted by the Pd-catalyzed asymmetric coupling of ene-alkoxyallenes and highly functionalized alcohol substrates. The reaction showed high chemo-, regio-, and ligand-driven diastereoselectivity.

Palladium-Catalyzed Asymmetric Decarboxylative Addition of β-Keto Acids to Heteroatom-Substituted Allenes.

The Pd-catalyzed asymmetric addition reaction of β-keto acids to heteroatom-substituted allene is reported. This reaction generates β-substituted ketones in an asymmetric manner through a branch-selective decarboxylative allylation pathway. The reaction accommodates various alkoxyallenes as well as amidoallenes.

Convergent Synthesis of Tetrasaccharide Fragment of Cervimycin K.

A new synthetic approach toward oligosaccharides consisting only of 2,3,6-trideoxypyranoglycosides is reported. The key feature is highlighted by the convergent approach that allows the introduction of the aglycon moiety in the late stage of the synthesis. As an illustrative example, the tetrasaccharide portion of cervimycin K was prepared as cyclohexyl glycoside.

Catalytic Asymmetric Synthesis of Hexahydro-furofuran-3-ol and Its Pyran Derivatives.

The catalytic asymmetric synthesis of hexahydro-furofuran-3-ol, a key fragment of HIV protease inhibitors, is reported. A signature event is represented by the sequential metal catalysis that combines the Pd-catalyzed asymmetric hydroalkoxylation of ene-alkoxyallene and ring-closing metathesis (RCM). Notably, this unprecedented and highly chemoselective approach allows for a unified access to pyranofuranol and furopyranol derivatives.

The growth-inhibitory effects of pawpaw (Asimina triloba [L.] Dunal) roots, twigs, leaves, and fruit against human gastric (AGS) and cervical (HeLa) cancer cells and their anti-inflammatory activities.

Background: The pawpaw tree has several beneficial effects. However, no studies have been conducted to address the mechanisms underlying the cytotoxic effects of pawpaw extracts against cancer cells, and no study has investigated the anti-inflammatory effects. Hence, in this study, the growth-inhibitory effects of pawpaw (Asimina triloba [L.

Concurrent Formation of N-H Imines and Carbonyl Compounds by Ruthenium-Catalyzed C-C Bond Cleavage of β-Hydroxy Azides.

A commercial cyclopentadienylrutenium dicarbonyl dimer ([CpRu(CO)]) efficiently catalyzes the formation of N-H imines and carbonyl compounds simultaneously from β-hydroxy azides via C-C bond cleavage under visible light. Density functional theory calculations for the cleavage reaction support the mechanism involving chelation of alkoxy azide species and liberation of nitrogen as the driving force. The synthetic utility of the reaction was demonstrated by a new amine synthesis promoted by chemoselective allylation of imine and synthesis of isoquinoline.

Ruthenium-Catalyzed Regioselective Olefin Migration of Dihydropyran Acetals: A Strategy toward β-2,6-Dideoxypyranoglycosides.

Here, we report a synthetic strategy toward β-2,6-dideoxypyranoglycosides. The key event is the ruthenium-catalyzed regioselective olefin migration of dihydropyran allylic acetals to homoallylic acetals. In combination with other metal-catalyzed reactions, this new protocol led to the synthesis of β-2,6-dideoxypyranoglycosides in a highly efficient manner.

Flexible Total Synthesis of 11-Deoxylandomycins and Their Non-Natural Analogues by Way of Asymmetric Metal Catalysis.

A de novo first collective total synthesis of 11-deoxylandomycins is reported. A signature step is featured by the Pd-catalyzed asymmetric addition of alcohol to ene-alkoxyallenes that assembles oligomeric 2,3,6-trideoxyoligosaccharides. The unique feature of the protocol is illustrated by a flexible access to various natural 11-deoxylandomycins as well as non-natural analogues.

Synthesis of Deoxyaminosugar Cyclohexyl-l-callipeltose and Its Diastereomer Using Pd-Catalyzed Asymmetric Hydroalkoxylation.

Cyclohexyl-l-callipeltose, an aminodeoxysugar subunit of Callipeltoside A, was synthesized in six steps and 40% overall yield from readily available ()-4-methylpent-4-en-2-ol and cyclohexyloxyallene. The signature step is represented by Pd-catalyzed asymmetric intermolecular hydroalkoxylation that generates the key dihydropyran intermediate upon combination with the ring-closing metathesis reaction. Notably, an unnatural diastereomer of the target compound could also be obtained with comparable efficiency simply by using the enantiomeric ligand.

Shape-dependent antimicrobial activities of silver nanoparticles.

An important application of silver nanoparticles (Ag NPs) is their use as an antimicrobial and wound dressing material. The aim of this study is to investigate the morphological dependence on the antimicrobial activity and cellular response of Ag NPs. Ag NPs of various shapes were synthesized in an aqueous solution using a simple method.

Phenolic Profiles, Antioxidant and Antimicrobial Activities of Pawpaw Pulp (Asimina triloba [L.] Dunal) at Different Ripening Stages.

In this study, the phenolic components, as well as the antioxidant and antimicrobial activities, of the ripe and unripe fruit of pawpaw (Asimina triloba [L.] Dunal) extracted using five different solvents (distilled water, 95% methanol, 80% methanol, 95% ethanol, and 80% ethanol) were analyzed. The total phenolic content and total flavonoid content were the highest in the 95% ethanol (149.

A Convergent Synthetic Strategy towards Oligosaccharides containing 2,3,6-Trideoxypyranoglycosides.

A de novo synthetic strategy for the production of oligosaccharides containing 2,3,6-trideoxypyranoglycoside is reported. The key event is the Pd-catalyzed asymmetric diastereoselective hydroalkoxylation of ene-alkoxyallene-linked glycosidic fragments. The utility of this approach was demonstrated by the activation-free, stereodivergent, and convergent synthesis of various 2-deoxyoligosaccharides, as well as their aglycon conjugates.

Preparation and Release Studies of Ibuprofen Loaded Nanoparticles Made from PHO and PEGMA--PHO.

Monoacrylate-poly(ethylene glycol) grafted poly(3-hydroxyoctanoate) (PEGMA--PHO) copolymer was obtained by UV irradiation and ibuprofen (IBU) loaded nanoparticles with PHO or PEGMA--PHO polymers were successfully prepared by a single emulsion process. Size of IBU-loaded nanoparticles was about 300 nm based on particle size measurement. Their shapes were spherical.

Correlation Between Acetogenin Content and Antiproliferative Activity of Pawpaw (Asimina triloba [L.] Dunal) Fruit Pulp Grown in Korea.

Unlabelled: Pawpaw (Asimina triloba [L.] Dunal) is widely cultivated in Korea for its fruit, which contains bioactive compounds, such as acetogenins. In this study, we investigated the acetogenin content and antiproliferative activity of pawpaw fruit pulp against various cancer cell lines and evaluated the relationship between these two variables at different maturation stages.

Palladium-Catalyzed Asymmetric Nitrogen-Selective Addition Reaction of Indoles to Alkoxyallenes.

A new palladium-catalyzed asymmetric addition reaction of indoles to alkoxyallenes is reported. Remarkably, the reaction showed complete regioselectivity toward the nitrogen. A new mechanism distinct from that of conventional π-allyl chemistry is proposed to explain this unique selectivity.

Ru-Catalyzed Chemoselective Olefin Migration Reaction of Cyclic Allylic Acetals to Enol Acetals.

A Ru-catalyzed olefin migration reaction of chiral cyclic allylic acetal is reported. The reaction generates cyclic enol acetal in a highly chemoselective manner. A variety of O,O- and N,O-acetals participated in the reaction with conservation of the stereochemical integrity of the acetal moiety.

Short Enantioselective Total Syntheses of Cheloviolenes A and B and Dendrillolide C via Convergent Fragment Coupling Using a Tertiary Carbon Radical.

The development of a convergent fragment coupling strategy for the enantioselective total syntheses of a group of rearranged spongian diterpenoids that harbor the cis-2,8-dioxabicyclo[3.3.0]octan-3-one unit is described.

Analysis of Medium-Chain-Length Polyhydroxyalkanoate-Producing Bacteria in Activated Sludge Samples Enriched by Aerobic Periodic Feeding.

Analysis of mixed microbial populations responsible for the production of medium-chain-length polyhydroxyalkanoates (MCL-PHAs) under periodic substrate feeding in a sequencing batch reactor (SBR) was conducted. Regardless of activated sludge samples and the different MCL alkanoic acids used as the sole external carbon substrate, denaturing gradient gel electrophoresis analysis indicated that Pseudomonas aeruginosa was the dominant bacterium enriched during the SBR process. Several P.