Highly Enantioselective Catalytic Lactonization at Nonactivated Primary and Secondary -C-H Bonds.

Chiral oxygenated aliphatic moieties are recurrent in biological and pharmaceutically relevant molecules and constitute one of the most versatile types of functionalities for further elaboration. Herein we report a protocol for straightforward and general access to chiral -lactones via enantioselective oxidation of strong nonactivated primary and secondary C()-H bonds in readily available carboxylic acids. The key enabling aspect is the use of robust sterically encumbered manganese catalysts that provide outstanding enantioselectivities (up to >99.

Site-selective methylene C-H oxidation of an alkyl diamine enabled by supramolecular recognition using a bioinspired manganese catalyst.

Site-selective oxidation of aliphatic C-H bonds is a powerful synthetic tool because it enables rapid build-up of product complexity and diversity from simple precursors. Besides the poor reactivity of alkyl C-H bonds, the main challenge in this reaction consists in differentiating between the multiple similar sites present in most organic molecules. Herein, a manganese oxidation catalyst equipped with two 18-benzo-6-crown ether receptors has been employed in the oxidation of the long chain tetradecane-1,14-diamine.

Carboxylic Acid Directed γ-Lactonization of Unactivated Primary C-H Bonds Catalyzed by Mn Complexes: Application to Stereoselective Natural Product Diversification.

Reactions that enable selective functionalization of strong aliphatic C-H bonds open new synthetic paths to rapidly increase molecular complexity and expand chemical space. Particularly valuable are reactions where site-selectivity can be directed toward a specific C-H bond by catalyst control. Herein we describe the catalytic site- and stereoselective γ-lactonization of unactivated primary C-H bonds in carboxylic acid substrates.

Resolving Oxygenation Pathways in Manganese-Catalyzed C(sp)-H Functionalization via Radical and Cationic Intermediates.

The C(sp)-H bond oxygenation of the cyclopropane-containing mechanistic probes 6--butylspiro[2.5]octane and spiro[2.5]octane with hydrogen peroxide catalyzed by manganese complexes bearing aminopyridine tetradentate ligands has been studied.

Remote Amino Acid Recognition Enables Effective Hydrogen Peroxide Activation at a Manganese Oxidation Catalyst.

Precise delivery of a proton plays a key role in O activation at iron oxygenases, enabling the crucial O-O cleavage step that generates the oxidizing high-valent metal-oxo species. Such a proton is delivered by acidic residues that may either directly bind the iron center or lie in its second coordination sphere. Herein, a supramolecular strategy for enzyme-like H O activation at a biologically inspired manganese catalyst, with a nearly stoichiometric amount (1-1.

Associations between sources of particle number and mortality in four European cities.

Background: The evidence on the association between ultrafine (UFP) particles and mortality is still inconsistent. Moreover, health effects of specific UFP sources have not been explored. We assessed the impact of UFP sources on daily mortality in Barcelona, Helsinki, London, and Zurich.

Spin State Tunes Oxygen Atom Transfer towards Fe O Formation in Fe Complexes.

Oxoiron(IV) complexes bearing tetradentate ligands have been extensively studied as models for the active oxidants in non-heme iron-dependent enzymes. These species are commonly generated by oxidation of their ferrous precursors. The mechanisms of these reactions have seldom been investigated.

General Access to Modified α-Amino Acids by Bioinspired Stereoselective γ-C-H Bond Lactonization.

α-Amino acids represent a valuable class of natural products employed as building blocks in biological and chemical synthesis. Because of the limited number of natural amino acids available, and of their widespread application in proteomics, diagnosis, drug delivery and catalysis, there is an increasing demand for the development of procedures for the preparation of modified analogues. Herein, we show that the use of bioinspired manganese catalysts and H O under mild conditions, provides access to modified α-amino acids via γ-C-H bond lactonization.

Enantioselective Epoxidation of β,β-Disubstituted Enamides with a Manganese Catalyst and Aqueous Hydrogen Peroxide.

Enantioselective epoxidation of β,β-disubstituted enamides with aqueous hydrogen peroxide and a novel manganese catalyst is described. Epoxidation is stereospecific and proceeds fast under mild conditions. Amides are disclosed as key functional groups to enable high enantioselectivity.

Biologically inspired oxidation catalysis using metallopeptides.

The stereoselective oxidation of hydrocarbons is one of the most challenging reactions for synthetic chemists. However, this transformation is one of the most common reactions in nature. Metalloenzymes that catalyze this transformation are taken as inspiration for the development of new catalysts.

DNA Repair Is Associated with Information Content in Bacteria, Archaea, and DNA Viruses.

The concept of a "proteomic constraint" proposes that DNA repair capacity is positively correlated with the information content of a genome, which can be approximated to the size of the proteome (P). This in turn implies that DNA repair genes are more likely to be present in genomes with larger values of P. This stands in contrast to the common assumption that informational genes have a core function and so are evenly distributed across organisms.

Nutrition and Physical Activity Interventions for Childhood Obesity: Lessons Learned.

This article describes field experiences while implementing nutrition and physical activity education in a public junior high school in Puerto Rico (PR). Participants were classified as overweight or at risk based on body mass index (BMI). Dietary intake and weight were collected.

The distribution of recombination repair genes is linked to information content in bacteria.

The concept of a 'proteomic constraint' proposes that the information content of the proteome exerts a selective pressure to reduce mutation rates, implying that larger proteomes produce a greater selective pressure to evolve or maintain DNA repair, resulting in a decrease in mutational load. Here, the distribution of 21 recombination repair genes was characterized across 900 bacterial genomes. Consistent with prediction, the presence of 17 genes correlated with proteome size.

Contributions of frontopolar cortex to judgments about self, others and relations.

Activation in frontopolar cortex (FPC; BA 10) has been associated both with attending to mental states and with integrating multiple mental relations. However, few previous studies have manipulated both of these cognitive processes, precluding a clear functional distinction among regions within FPC. To address this issue, we developed an fMRI task that combined mentalizing and relational integration processes.

An extract of the Chinese herbal root kudzu reduces alcohol drinking by heavy drinkers in a naturalistic setting.

Background: Of the available medications for treating alcohol-related problems, none are universally effective, and all have side effects that may limit their use. Extracts of kudzu containing a variety of isoflavones have been shown to reduce alcohol drinking in rats and hamsters.

Methods: The present study was designed to test the efficacy of a kudzu extract in a clinical population.