Universal Reaction Mechanism of Boronic Acids with Diols in Aqueous Solution: Kinetics and the Basic Concept of a Conditional Formation Constant

To establish a detailed reaction mechanism for the condensation between a boronic acid, RB(OH)₂, and a diol, H₂L, in aqueous solution, the acid dissociation constants (${K{{{\rm BL}\hfill \atop {\rm a}\hfill}}}$ ) of boronic acid diol esters (HBLs) were determined based on the well‐established concept of conditional formation constants of metal complexes. The pK_a values of HBLs were 2.30, 2.77, and 2.00 for the reaction systems, 2,4‐difluorophenylboronic acid and chromotropic acid, 3‐nitrophenylboronic acid and alizarin red S, and phenylboronic acid and alizarin red S, respectively. A general and precise reaction mechanism of RB(OH)₂ with H₂L in aqueous solution, which can serve as a universal reaction mechanism for RB(OH)₂ and H₂L, was proposed on the basis of (a) the relative kinetic reactivities of the RB(OH)₂ and its conjugate base, that is, the boronate ion, toward H₂L, and (b) the determined pK_a values of HBLs. The use of the conditional formation constant, K′, based on the main reaction: RB(OH)₂+H₂L ${{\mathop \leftrightarrow \limits ^{K{_{1}}}_{}}}$ RB(L)(OH)^?+H₃O⁺ instead of the binding constant has been proposed for the general reaction of uncomplexed boronic acid species (B′) with uncomplexed diol species (L′) to form boronic acid diol complex species (esters, BL′) in aqueous solution at pH 5–11: B′+L′ ${{\mathop \leftrightarrow \limits ^{K{^\prime}}_{}}}$ BL′. The proposed reaction mechanism explains perfectly the formation of boronic acid diol ester in aqueous solution.     

An Efficient Synthetic Method for 2-Methoxy-L,2-dihydro-3H-indol-3-ones

An efficient method for synthesis of 2-methoxy-l,2-dihydro-3H-indol-3-ones using two successive oxidations of indoles is described.     

Palladium(0)-catalyzed cis-selective alkylative and arylative cyclization of alkynyl enones with organoboron reagents

A palladium(0)-tricyclohexylphosphine catalyzes cis-selective alkylative and arylative cyclization of alkyne-containing electron-deficient alkenes with organoboron reagents to provide five- or six-membered rings with exo tri- or tetra-substituted alkenes. The opposite stereoselectivity to that for the alkyne-aldehyde cyclization using the same reagents would result from palladacycle-forming oxidative addition of the substrates to the Pd⁰ catalyst followed by transmetalation with the boron reagents, protonation, and reductive elimination. The functional group compatibility, availability, stability, and non-toxicity of the reagents, and the fact that no additives are needed make the process more practical than the Ni⁰-catalyzed cyclization with organozinc reagents.     

Biosynthesis of a novel cyclic C35-terpene via the cyclisation of a Z-type C35-polyprenyl diphosphate obtained from a nonpathogenic Mycobacterium species

Lipid components from 12 nonpathogenic Mycobacterium species were analysed. A novel cyclic C(35)-terpene, named heptaprenylcycline , was obtained from 3 species, while octahydroheptaprenol , which has 3 Z-double bonds, was obtained from 6 species. The amounts of and in the cultured cells increased after the 4- to 6-d stationary phase. The yield of was considerably greater at a higher temperature of 37 degrees C than at an optimal temperature of 28 degrees C, while that of remained unchanged at all temperatures. A feeding experiment with d-[1-(13)C]glucose revealed that was produced via isopentenyl diphosphate, which is a metabolite of glycolysis and the methylerythritol phosphate pathway. The conversion of octahydroheptaprenyl diphosphate to was successful by using the cell-free extracts of M. chlorophenolicum, demonstrating that is the biosynthetic intermediate of . This is the first example of the biosynthesis of a natural terpene via the cyclisation of a linear C(35)-isoprenoid. The substrate for C(35)-terpene cyclase has Z-type prenyl moieties; however, terpene cyclases usually employ E-type isoprenoids. The gene encoding the terpene cyclase that cyclises prenyl diphosphate containing Z-double bonds as the natural substrate has not yet been detected. Despite a careful search using the FASTA3 program, we could not detect any gene that is homologous to the known diphosphate-triggered type of mono-, sesqui- and diterpene cyclases in the genome of M. vanbaalenii, the DNA sequence of which has recently been elucidated. This suggests that a novel type of terpene cyclase might exist in the nonpathogenic Mycobacterium species.     

Development of a mass spectrometric hydroxyl‐position determination method for the hydroxyindole metabolites of JWH‐018 by GC‐MS/MS

One of the many issues of designer drugs of abuse like synthetic cannabinoids (SCs) such as JWH‐018 is that details on their metabolism has yet to be fully elucidated and that multiple metabolites exist. The presence of isomeric compounds poses further challenges in their identification. Our group has previously shown the effectiveness of gas chromatography‐electron ionization‐tandem mass spectrometry (GC‐EI‐MS/MS) in the mass spectrometric differentiation of the positional isomers of the naphthoylindole‐type SC JWH‐081, and speculated that the same approach could be used for the metabolite isomers. Using JWH‐018 as a model SC, the aim of this study was to differentiate the positional isomers of its hydroxyindole metabolites by GC‐MS/MS. Standard compounds of JWH‐018 and its hydroxyindole metabolite positional isomers were first analyzed by GC‐EI‐MS in full scan mode, which was only able to differentiate the 4‐hydroxyindole isomer. Further GC‐MS/MS analysis was performed by selecting m/z 302 as the precursor ion. All four isomers produced characteristic product ions that enabled the differentiation between them. Using these ions, MRM analysis was performed on the urine of JWH‐018 administered mice and determined the hydroxyl positions to be at the 6‐position on the indole ring. GC‐EI‐MS/MS allowed for the regioisomeric differentiation of the hydroxyindole metabolite isomers of JWH‐018. Furthermore, analysis of the fragmentation patterns suggests that the present method has high potential to be extended to hydroxyindole metabolites of other naphthoylindole type SCs in identifying the position of the hydroxyl group on the indole ring. Copyright © 2016 John Wiley & Sons, Ltd.     

Structural development of liver X receptor (LXR) antagonists derived from thalidomide-related glucosidase inhibitors

Following our previous discovery of LXR antagonistic activity of 2'-substituted phenylphthalimides derived from thalidomide-related glucosidase inhibitors, structure-activity studies and further structural development led to 5-chloro-N-2'-n-pentylphenyl-1,3-dithiophthalimide (5CPPSS-50), with IC50 values of about 10 and 13 microM for LXRalpha and LXRbeta, respectively.     

Hydrolyzed metabolites of thalidomide: synthesis and TNF-alpha production-inhibitory activity

Putative hydrolyzed metabolites of thalidomide were prepared and characterized, and their inhibitory activity on tumor necrosis factor (TNF)-alpha production in the human monocytic leukemia cell line THP-1 was evaluated. Alpha-(2-Carboxybenzamido)glutarimide was a more potent TNF-alpha production inhibitor than thalidomide.     

Light-scattering detection with a fluorimetric detector in high-performance liquid chromatography

Non-fluorescence compounds were detected by a fluorescence detector based on scattering light. The fluorescence detector was used without any modification, and the scattering light was observed at the wavelength twice as long as the excitation wavelength. Actually the wavelength of the observed scattering light was the same as that of the excitation light. The maximum signal was achieved at around 280 nm. The signal was increased with increasing molecular weight or size of analytes. Colloidal silica with nanometer sizes, ethylene glycol oligomers, saccharides and cyclodextrins could be visualized by the present detection method. The detection limit at S/N=3 for colloidal silica with 78 nm was 39 pg for 20-microL injection.     

Simple one-step extraction and cleanup by pressurized liquid extraction for gas chromatographic-mass spectrometric determination of pesticides in green leafy vegetables

A simple one-step extraction and cleanup using a pressurized liquid extraction method was developed for the gas chromatographic-mass spectrometric determination of pesticides in vegetables. The pressurized liquid extraction conditions were optimized and cleanup agents were evaluated. The investigated pesticides included six insecticides, chlorpyrifos methyl, pirimiphos-methyl, malathion, chlorpyrifos, O-ethyl O-4-nitrophenylphenyl phosphonothioate (EPN) and permethrins, a fungicide, isoprothiolane, and a herbicides, thiobencarb. The cleanup agent and a mixture of the vegetable and anhydrous sodium sulfate were separately packed in an extraction vessel. A transparent and colorless extract was obtained using graphitized carbon as the cleanup agent. The overall recoveries were 71-103% and the relative standard deviations ranged from 5.6 to 24%. The limit of detection values were 3-8 microg kg(-1). This method was successfully applied to green leafy vegetables.     

Resin-packed nanoelectrospray in combination with video and mass spectrometry for the direct and real-time molecular analysis of mast cells

A nano-electrospray ionization (nanoESI) emitter for analysis of a biological solution was developed by packing a nanoESI needle with two types of resins for desalting and preconcentration of target molecules. Determination of secreted histamine and serotonin molecules in cell culture buffers was demonstrated using 5-methyltryptamine as internal standard. The results showed good linearity of target signals in the concentration range from 0.25 to 50.0 ng/mL of histamine or serotonin. These molecules were monitored to be secreted by A23187 (calcium ionophore) stimulant in rat peritoneal mast cells. Using a combination of a video-microscope and a mass spectrometer, we could visualize exocytotic moments and analyze secreted molecules by mass spectrometry simultaneously. Time-dependent release of histamine and serotonin from activated mast cells showed that significant production of these molecules occurred and reached a maximal level at 15 min for serotonin and at 30 min for histamine, respectively. These results showed that this method allows the direct and timely analysis of secreted molecules in biological responses.