A new iridoid glycoside with nerve growth factor-potentiating activity,gelsemiol 6'-trans-caffeoyl-1-glucoside,from Verbena littoralis

A new iridoid glycoside, gelsemiol 6'-trans-caffeoyl-1-glucoside (1), was isolated from Verbena littoralis, together with four known phenylethanoid glycosides, acteoside (2), 2'-acetylacteoside (3), jionoside (4), and isoverbascoside (5). Their structures were elucidated by spectral data. Compound 1 showed weak enhancement of nerve growth factor (NGF)-mediated neurite outgrowth from PC12D cells.     

Allosteric Binding of an Ag+ Ion to Cerium(IV) Bis-porphyrinates Enhances the Rotational Activity of Porphyrin Ligands

A series of cerium(IV) bisporphyrinate double-deckers [Ce(bbpp)2] (BBPP = 5,15-bis(4-butoxyphenyl) porphyrin dianion), [Ce(tmpp)2] (TMPP = 5,10,15,20-tetrakis(4-methoxyphenyl)-porphyrin dianion), [Ce(tfpp)2] (TFPP = 5,10,15,20-tetrakis(4-fluorophenyl)porphyrin dianion), [Ce(tmcpp)2] (TMCPP = 5,10,15,20-tetrakis(4-methoxycarbonylphenyl)porphyrin dianion), and [Ce(tmpp)(tmcpp)] was prepared. They bind three Ag+ ions to their concave porphyrin pi subunits (pi-clefts) according to a positive homotropic allosteric mechanism with Hill coefficients (nH) of 1.7-2.7. The rotation rates of the porphyrin ligands in [Ce(bbpp)2] were evaluated to be 200 s-1 at 20 degrees C (delta G++293 = 14.1 kcal mol-1) and 220 s-1 at -40 degrees C (delta G++233 = 11.0 kcal mol-1) without and with Ag+ ions, respectively. These results consistently support our unexpected finding that Ag+ binding can accelerate rotation of the porphyrin ligand. On the basis of UV-visible, 1H NMR, and resonance Raman spectral measurements, the rate enhancement of the rotational speed of the porphyrin ligands is attributed to conformational changes of the porphyrin in cerium(IV) bis-porphyrinate induced by binding of Ag+ guest ions in the clefts. This novel concept of positive homotropic allosterism is applicable to the molecular design of various supramolecular and switch-functionalized systems.     

Synthesis of a 1,1-dimethylcarbapen-2-em derivative via an aldol-type cyclization

The synthesis of 1,1-dimethylcarbapen-2-em derivative $\text{3}$ is described. The key step in the synthesis is an intramolecular aldol-type condensation reaction.     

Conversion of anisotropically phase-segregated Pd/gamma-Fe2O3 nanoparticles into exchange-coupled fct-FePd/alpha-Fe nanocomposite magnets

Exchange-coupled fct-FePd/alpha-Fe nanocomposite magnets were fabricated by converting anisotropically phase-segregated Pd/gamma-Fe2O3 nanoparticles via the interfacial atom diffusion. The magnetically hard fct-FePd phases formed by the interdiffusion between alpha-Fe and fcc-Pd phases nearly preserve their sizes at the nanometer scale because they are surrounded by the alpha-Fe matrix. The VSM measurements reveal that the exchange coupling between the soft and hard phases has been realized.     

Highly selective 30% hydrogen peroxide oxidation of sulfides to sulfoxides using micromixing

The highly selective oxidation of sulfides to sulfoxides using 30% hydrogen peroxide has been achieved under catalyst-free conditions using a T-shaped micromixer.     

Study on the nitric oxide generating effects from aristolochic acid in vitro

In this study, an in vitro nitric oxide (NO)-assay system based on the Griess reaction was used to investigate the (NO)-generating effects of aristolochic acid (AA) for the first time. AA was separated into its different components, aristolochic acid I (AAI) and aristolochic acid II (AAII), by preparative HPLC. AAI and AAII were incubated with human intestine bacteria (HIB) or rat intestine bacteria (RIB). A NO mixture generated from AAI and AAII by intestinal bacteria was observed and denitroso metabolites of AAI or AAII were detected in vitro by liquid chromatography/tandem mass spectrometry. Therefore, NO generation might be closely related to the metabolic process of AA in vitro. It suggested that one possible mechanism for the toxicity of AA may be due to the generation of NO from these compounds by intestinal bacteria.     

Brevisamide: an unprecedented monocyclic ether alkaloid from the dinoflagellate Karenia brevis that provides a potential model for ladder-frame initiation

The dinoflagellate Karenia brevis is known for the production of brevetoxins, a family of polycyclic ether toxins, as well as their antagonist brevenal. Further examination of organic extracts of K. brevis has uncovered yet another unprecedented cyclic ether alkaloid named brevisamide. This report describes the structure elucidation of brevisamide based on detailed MS and NMR spectral analysis, and the importance of this new compound in shedding light on the biogenesis of fused polyethers is discussed.     

Synthetic studies on maitotoxin. 2. Stereoselective synthesis of the WXYZA'-ring system

The stereoselective synthesis of the WXYZA'-ring system of maitotoxin has been accomplished via a linear synthetic approach, in which key reactions were SmI 2-induced cyclization of beta-alkoxyacrylate for the construction of the A'-, Y-, and X-rings and 6- endo cyclization of hydroxy vinylepoxide for that of the Z- and W-rings.     

Miuraenamides: Antimicrobial Cyclic Depsipeptides Isolated from a Rare and Slightly Halophilic Myxobacterium

Marine myxobacteria are rare culture‐resistant microorganisms, several strains of which have been identified by research groups in Asia. Paraliomyxa miuraensis, a slightly halophilic myxobacterium discovered in Japan, produces the cyclic hybrid polyketide–peptide antibiotics known as miuraenamides A and B, whose taxonomical and biological characteristics have been reported previously. Herein, we describe the chemical characterization of these two miuraenamides and introduce four new members of the miuraenamide family. We carried out the complete structural analysis of miuraenamides A and B on the basis of NMR spectroscopic analysis and elucidated the absolute configuration of miuraenamide A by chemical derivatization and subsequent use of the modified Mosher method or the Marfey method. Miuraenamides C–F were isolated from the same strain of the bacterium as miuraenamides A and B. The structure–antimicrobial‐activity relationships of the six natural metabolites and four chemically derived compounds demonstrated the importance of both the macrocyclic structure and the β‐methoxyacrylate moiety.