Isolation of heptadepsin, a novel bacterial cyclic depsipeptide that inhibits lipopolysaccharide activity

Lipopolysaccharide (LPS) is considered to cause various inflammatory reactions. We searched among microbial secondary metabolites for compounds that could inhibit LPS-stimulated adhesion between human umbilical vein endothelial cells (HUVEC) and human myelocytic cell line HL-60 cells. In the course of our screening, we isolated a novel cyclic depsipeptide, which we named heptadepsin, from the whole culture broth of Paenibacillus sp. The addition of heptadepsin prior to LPS stimulation decreased HL-60 cell-HUVEC adhesion without showing any cytotoxicity. It also inhibited the cellular adhesion induced by lipid A, the active component of LPS, but it did not inhibit TNF-alpha or IL-1beta-induced cell adhesion. The result of surface plasmon resonance (SPR) analysis revealed that heptadepsin interacted with lipid A directly. Thus, heptadepsin, a novel naturally occurring cyclic heptadepsipeptide, was shown to inactivate LPS by direct interaction with LPS.     

Kinetically controlled Ag+-coordinated chiral supramolecular polymerization accompanying a helical inversion

We report kinetically controlled chiral supramolecular polymerization based on ligand–metal complex with a 3 : 2 (L : Ag⁺) stoichiometry accompanying a helical inversion in water. A new family of bipyridine-based ligands (d-L1, l-L1, d-L2, and d-L3) possessing hydrazine and d- or l-alanine moieties at the alkyl chain groups has been designed and synthesized. Interestingly, upon addition of AgNO₃ (0.5–1.3 equiv.) to the d-L1 solution, it generated the aggregate I composed of the d-L1AgNO₃ complex (d-L1 : Ag⁺ = 1 : 1) as the kinetic product with a spherical structure. Then, aggregate I (nanoparticle) was transformed into the aggregate II (supramolecular polymer) based on the (d-L1)₃Ag₂(NO₃)₂ complex as the thermodynamic product with a fiber structure, which led to the helical inversion from the left-handed (M-type) to the right-handed (P-type) helicity accompanying CD amplification. In contrast, the spherical aggregate I (nanoparticle) composed of the d-L1AgNO₃ complex with the left-handed (M-type) helicity formed in the presence of 2.0 equiv. of AgNO₃ and was not additionally changed, which indicated that it was the thermodynamic product. The chiral supramolecular polymer based on (d-L1)₃Ag₂(NO₃)₂ was produced via a nucleation–elongation mechanism with a cooperative pathway. In thermodynamic study, the standard ΔG° and ΔH_e values for the aggregates I and II were calculated using the van''t Hoff plot. The enhanced ΔG° value of the aggregate II compared to that of the formation of aggregate I confirms that aggregate II was thermodynamically more stable. In the kinetic study, the influence of concentration of AgNO₃ confirmed the initial formation of the aggregate I (nanoparticle), which then evolved to the aggregate II (supramolecular polymer). Thus, the concentration of the (d-L1)₃Ag₂(NO₃)₂ complex in the initial state plays a critical role in generating aggregate II (supramolecular polymer). In particular, NO₃⁻ acts as a critical linker and accelerator in the transformation from the aggregate I to the aggregate II. This is the first example of a system for a kinetically controlled chiral supramolecular polymer that is formed via multiple steps with coordination structural change.

The nanoparticles were transformed into the supramolecular polymer as the thermodynamic product, involving a helical inversion from left-handed to right-handed helicity.     

Enantioface-selective palladium-catalyzed silaboration of allenes via double asymmetric induction

Enantioenriched beta-borylallylsilanes were synthesized by palladium-catalyzed enantioface-selective addition of the silicon-boron bond to terminal allenes using a palladium catalyst possessing a chiral monodentate phosphine ligand. Use of a silylborane bearing a chiral auxiliary on the boron atom was beneficial to gain enantioface selectivities as high as 96% de.     

Interaction of organic dyes and proteins-determination of the binding constants spectrophotometrically

Summary The spectral change of a small molecule (S) induced by addition of a large molecule (P) was examined theoretically and experimentally, assuming that the interaction betweenS andP follows theLangmuir adsorption isotherm. It was found that intermolecular binding constants could be determined accurately and conveniently by extrapolation to zero of two simple graphic relations, namely, the observed molar extinction coefficient ofS in the presence ofP versus the ratio of (the concentration ofS/the concentration ofP), and of the former versus the reciprocal value of the latter. This spectrophotometric method was applied to the binding of bovine serum albumin and Ponceau3 R and of bovine serum albumin and HABA at p_H 7.0. The results obtained by this method were comparable with those obtained by equilibrium dialysis or by conventional spectrophotometric method.

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Zusammenfassung Unter der Annahme, daß dieLangmuirsche Absorptionsisotherme auch bei der Assoziation hoch-(HMV) und niedermolekularer Verbindungen (NMV) gilt, wurden die Bindungskonstanten bestimmt. Es wurden die spektralen Änderungen in der UV-Absorption der NMV bei Zusatz verschiedener HMV-Mengen gemessen. Die Bindungskonstanten lassen sich durch Kombination zweier graphischer Darstellungen exakt und einfach bestimmen: erstens aus der Beziehung zwischen dem molaren Extinktionskoeffizienten der NMV in Anwesenheit verschiedener HMV-Konzentrationen und dem Konzentrationsverhältnis von NMV zu HMV und zweitens aus dem Zusammenhang der molaren Extinktionskoeffizienten mit den reziproken Werten des oben genannten Konzentrationsverhältnisses. Mit dieser neuen Methode wurden die Bindungskonstanten bei p_h 7.0 von Rinderserumalbumin und Ponceau 3 R bzw. HABA berechnet und mit den durch andere Methoden bestimmten Konstanten verglichen. Die Werte stimmen mit denen aus der Dialysemethode und aus der üblichen spektralphotometrischen Methode überein.

     

Production of highly specific anti-testosterone antiserum by an immunotolerance method

Anti-testosterone antisera were produced by pretreatment of rabbits with 15 alpha-carboxymethyl-5 alpha-dihydrotestosterone linked to a copolymer of D-glutamic acid and D-lysine (D-GL) before immunization with the bovine serum albumin conjugate of 15 alpha- and 15 beta-carboxymethyltestosterone. The specificity for 5 alpha-dihydrotestosterone of the antitestosterone antisera was considerably improved.     

Mononuclear five-coordinate molybdenum(IV) and -(V) monosulfide complexes coordinated with dithiolene ligands: reversible redox of Mo(V)/Mo(IV) and irreversible dimerization of [MoVS]- cores to a dinuclear [MoV2(mu-S)2]2- Core

A mononuclear five-coordinate molybdenum(IV) monosulfide complex, (Et4N)2[MoS(L)2] (L = cyclohexene-1,2-dithiolate) (1), was obtained and characterized by IR, UV-vis spectroscopic methods, and X-ray crystallography. 1 was oxidized by an equivalent ferrocenium cation to give the corresponding mononuclear molybdenum(V) complex, (Et4N)[MoS(L)2] (2), which was stable for a few minutes under a lower concentration than 0.3 mM and then further dimerized to (Et4N)2[Mo(L)2]2(mu-S)2 (3).     

Chemoenzymatic synthesis of (+)-totarol, (+)-podototarin, (+)-sempervirol, and (+)-jolkinolides E and D

The enzymatic resolution products [(1R,4aR,8aR)-1,2,3,4,4a,5,6,7,8,8a-decahydro-5,5,8a-trimethyl-2-oxo-trans-naphthalene-1-methanol-2-ethylene acetal (8aR)-7 (98% ee) and {acetate of (1S,4aS,8aS)-1,2,3,4,4a,5,6,7,8,8a-decahydro-5,5,8a-trimethyl-2-oxo-trans-naphthalene-1-methanol-2-ethylene acetal} (8aS)-9 (>99% ee)] obtained by the lipase-catalyzed enantioselective acetylation of (±)-7 in the presence of vinyl acetate as an acyl donor were converted to the ,β-unsaturated ketones (8aR)-6 and (8aS)-6, respectively. Concise syntheses of (+)-totarol 1, (+)-podototarin 2 and (+)-sempervirol 3 were achieved based on Michael reactions between (8aS)-6 and the appropriate β-keto ester followed by aldol condensation. The first chiral syntheses of (+)-jolkinolides E 4 and D 5 were achieved from (5R,10R,12R)-12-hydroxypodocarpa-8(14)-en-13-one 15 derived from (8aR)-6.     

A Convenient Preparation of p-Chloromethyl-Styrene and its Reactions

In the present communication we would like to describe a novel method for the preparation of p-chloromethylstyrene and some reactions of this compound.     

Thermal and evolved gas analyses of the oxidation of a cellulose/copper(II) oxide mixture

Cellulosic biomass is a promising alternative energy resource from the viewpoint of sustainability. The use of waste materials as cellulosic biomass could additionally contribute to a recycling society. It is thus essential to develop safer processes in order to expand utilization of cellulosic biomass as a useful resource in the future. For example, in some cases, construction wastes contain wood preservatives, including metal oxides that can act as catalysts for the oxidation of organic materials. Copper(II) oxide (CuO) is a major component in wood preservatives and is known to catalyze the oxidation of cellulose. There is, therefore, possibility for spontaneous ignition within large piles of wood chips from construction wastes. In this study, we focused on the thermal behavior of a cellulose/CuO mixture, measured using a Calvet-type heat flux calorimeter. In addition, Fourier transform infrared spectroscopy and gas chromatography were applied to analyze the oxidative decomposition gases of the cellulose/CuO mixture, and a reaction mechanism was proposed. It was revealed that CuO promotes the oxidative decomposition of cellulose and increases the quantity of the gases that evolved from cellulose with a catalytic cycle. The influence of CuO on oxidation of cellulose is greater at lower temperatures and spontaneous ignition, fires, and explosions are likely to increase when wood chips containing CuO are stored for long periods of time.