Bobbitt's Salt-Mediated Oxidation of Alkynyl-ols and -diols to the Corresponding Aldehydes and Their Application in Tandem Reactions.

Propargyl alcohol derivatives were readily oxidized using Bobbitt's salt to yield the corresponding propynal products. 2-Butyn-1,4-diol may be selectively oxidized to provide either 4-hydroxy-2-butynal or acetylene dicarboxaldehyde, and the resulting stable dichloromethane solutions containing the chemically sensitive acetylene aldehydes were used directly in subsequent Wittig, Grignard, or Diels-Alder reactions. This method provides safe and efficient access to propynals and allows the preparation of polyfunctional acetylene compounds from readily accessible starting material without the use of protecting groups.

Self-assembled materials from cellulose nanocrystals conjugated with a thermotropic liquid crystalline moiety.

Manipulating molecular and supramolecular interactions within cellulose nanocrystals (CNCs) to introduce different levels of assemblies combined with multiple functionalities is required for the development of degradable smart materials from renewable resources. To attain hierarchical structures and stimuli-responsive properties, a new class of liquid crystalline cellulosic hybrid materials is synthesized. Herein, main-chain rigid-rod-like oxidized cellulose (CNC-COOH) is prepared from a Cellulose Whatman filter paper (Cellulose W.P.) by acid hydrolysis and oxidized using 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO). Thermotropic LC molecule, 4-cyano-4'-hydroxybiphenyl with a 12-methylene spacer (CB12-OH) is grafted onto the carboxylic acid group of CNC-COOH via Steglich esterification. The liquid crystalline functionalized CNCs cellulose nanocrystals (CNC-COO-CB12) are readily soluble in DMSO and ionic liquids. The extent of functionalization and structure of CNC-COO-CB12 are confirmed by solution-state 1H NMR and supported by other characterization techniques. We investigate the interplay of liquid crystalline orientational order of CNCs and cyanobiphenyl (CB12), and the supramolecular hydrogen bonding of CNCs within CNC-COO-CB12 and compare it with CNC-COOH. The introduction of thermotropic CB12 side chains onto rigid-rod CNCs shows the exclusive formation of smectic mesophases from the assemblies of CB12 with the absence of the cholesteric mesophase typically observed from CNC-COOH as verified by temperature-controlled SAXS (T-SAXS). This is further verified by UV-visible and SEM studies that show CNC-COO-CB12 forms smectic domains while CNC-COOH forms a visible light reflecting cholesteric mesophase in dried films. Thus, the interplay of liquid crystalline order of CNCs and CB12 and supramolecular hydrogen bonding of CNCs results in ordered, smectic-mesostructured CNCs for use in stimuli-responsive functional materials.

The mitochondria-targeted peptide SS-31 binds lipid bilayers and modulates surface electrostatics as a key component of its mechanism of action.

Mitochondrial dysfunction underlies many heritable diseases, acquired pathologies, and aging-related declines in health. Szeto-Schiller (SS) peptides comprise a class of amphipathic tetrapeptides that are efficacious toward a wide array of mitochondrial disorders and are believed to target mitochondrial membranes because they are enriched in the anionic phospholipid cardiolipin (CL). However, little is known regarding how SS peptides interact with or alter the physical properties of lipid bilayers. In this study, using biophysical and computational approaches, we have analyzed the interactions of the lead compound SS-31 (elamipretide) with model and mitochondrial membranes. Our results show that this polybasic peptide partitions into the membrane interfacial region with an affinity and a lipid binding density that are directly related to surface charge. We found that SS-31 binding does not destabilize lamellar bilayers even at the highest binding concentrations; however, it did cause saturable alterations in lipid packing. Most notably, SS-31 modulated the surface electrostatics of both model and mitochondrial membranes. We propose nonexclusive mechanisms by which the tuning of surface charge could underpin the mitoprotective properties of SS-31, including alteration of the distribution of ions and basic proteins at the interface, and/or modulation of bilayer physical properties. As a proof of concept, we show that SS-31 alters divalent cation (calcium) distribution within the interfacial region and reduces the energetic burden of calcium stress in mitochondria. The mechanistic details of SS-31 revealed in this study will help inform the development of future compound variants with enhanced efficacy and bioavailability.

Preparation of Some Homologous TEMPO Nitroxides and Oxoammonium Salts; Notes on the NMR Spectroscopy of Nitroxide Free Radicals; Observed Radical Nature of Oxoammonium Salt Solutions Containing Trace Amounts of Corresponding Nitroxides in an Equilibrium Relationship.

Three new homologous TEMPO oxoammonium salts and three homologous nitroxide radicals have been prepared and characterized. The oxidation properties of the salts have been explored. The direct 13C NMR and EPR spectra of the nitroxide free radicals and the oxoammonium salts, along with TEMPO and its oxoammonium salt, have been successfully measured with little peak broadening of the NMR signals. In the spectra of all ten compounds (nitroxides and corresponding oxoammonium salts), the carbons in the 2,2,6,6-tetramethylpiperidine core do not appear, implying paramagnetic properties. This unpredicted overall paramagnetism in the oxoammonium salt solutions is explained by a redox equilibrium as shown between oxoammonium salts and trace amounts of corresponding nitroxide. This equilibrium is confirmed by electron interchange reactions between nitroxides with an N-acetyl substituent and oxoammonium salts with longer acyl side chains.

Methodology for the Construction of the Bicyclo[4.3.0]nonane Core.

The bicyclo[4.3.0]nonane scaffold, commonly known as a hydrindane, is a common structural motif found in many terpenoid structures and one that remains a challenge for synthetic chemists to elaborate with appropriate regio- and stereo-selectivity. Over the course of the study of terpene natural products, the elaboration of the hydrindane structure has seen progress on the utilization of both old and newer methods to achieve the desired outcomes. This review seeks to serve as a general overview of these methods, and detail specific examples.

Partial oxidation of methane to methanol on boron nitride at near critical acetonitrile.

Direct catalytic conversion of methane to methanol with O2 has been a fundamental challenge in unlocking abundant natural gas supplies. Metal-free methane conversion with 17% methanol yield based on the limiting reagent O2 at 275 °C was achieved with near supercritical acetonitrile in the presence of boron nitride. Reaction temperature, catalyst loading, dwell time, methane-oxygen molar ratio, and solvent-oxygen molar ratios were identified as critical factors controlling methane activation and the methanol yield. Extension of the study to ethane (C2) showed moderate yields of methanol (3.6%) and ethanol (4.5%).

The oxazolidinone derivative locostatin induces cytokine appeasement.

Damaging inflammation arising from autoimmune pathology and septic responses results in severe cases of disease. In both instances, anti-inflammatory compounds are used to limit the excessive or deregulated cytokine responses. We used a model of robust T cell stimulation to identify new proteins involved in triggering a cytokine storm. A comparative proteomic mining approach revealed the differential mapping of Raf kinase inhibitory protein after T cell recall in vivo. Treatment with locostatin, an Raf kinase inhibitory protein inhibitor, induced T cell anergy by blocking cytokine production after Ag recall. This was associated with a reduction in Erk phosphorylation. Importantly, in vivo treatment with locostatin profoundly inhibited TNF-alpha production upon triggering the Ag-specific T cells. This effect was not limited to a murine model because locostatin efficiently inhibited cytokine secretion by human lymphocytes. Therefore, locostatin should be a useful therapeutic to control inflammation, sepsis, and autoimmune diseases.

Access to dienophilic ene-triketone synthons by oxidation of diketones with an oxoammonium salt.

Here we describe the oxidation of 1,3-cyclohexanediones with 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate (Bobbitt's salt) to generate 5-ene-1,2,4-triones in moderate-to-good (40-80%) yields. This inexpensive oxidant facilitated an unprecedented cascade of oxidation and elimination to yield novel ene-triketones. The reactivity of these products was explored in the Diels-Alder reaction and provided moderate-to-good yields of cycloaddition products. The products described in this study represent unique, densely functionalized, and versatile building blocks for the synthesis of more complex molecules.

Recognition and reactivity in the binding between Raf kinase inhibitor protein and its small-molecule inhibitor locostatin.

The present work is aimed to provide detail on the binding process between Raf kinase inhibitor protein (RKIP) and locostatin, the only exogenous compound known to alter the function of RKIP. Understanding the basis of RKIP inhibition for use in pharmacological applications is of considerable interest, as dysregulated RKIP expression has the potential to contribute to pathophysiological processes. Herein, we report a series of atomistic models to describe the protein-ligand recognition step and the subsequent reactivity steps. Modeling approaches include ligand docking, molecular dynamics, and quantum mechanics/molecular mechanics calculations. We expect that such a computational assay will serve to study similar complexes in which potency is associated with recognition and reactivity. Although previous data suggested a single amino acid residue (His86) to be involved in the binding of locostatin, the actual ligand conformation and the steps involved in the reactivity process remain elusive from a detailed atomistic description. We show that the first reaction step, consisting of a nucleophilic attack of the nitrogen (Nε) of His86 at the sp(2)-hybridized carbon (C2) of locostatin, presents a late transition state (almost identical to the product). The reaction is followed by a hydrogen abstraction and hydrolysis. The theoretically predicted overall rate constant (6 M(-1) s(-1)) is in a very good agreement with the experimentally determined rate constant (13 M(-1) s(-1)).

Synthesis of Oxazolidinone and Tosyl Enamines by Tertiary Amine Catalysis.

A procedure for the synthesis of oxazolidinone and tosyl enamines is reported. Alkynoyl oxazolidinones and tosyl imides undergo reaction to form enamines in the presence of catalytic amounts of tertiary amines. The data suggest that an amide anion is formed during the reaction, which undergoes conjugate addition to form the final product.