Simultaneous determination of testosterone, cortisol, and dehydroepiandrosterone in saliva by stable isotope dilution on-line in-tube solid-phase microextraction coupled with liquid chromatography–tandem mass spectrometry

We have developed a simple and sensitive method for the simultaneous determination of testosterone (TES), cortisol (CRT), and dehydroepiandrosterone (DHEA) in saliva by automated online in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–tandem mass spectrometry (LC–MS/MS) using a Discovery HS F5 column. The optimum in-tube SPME conditions were 25 draw/eject cycles of 40 μL of sample at a flow rate of 200 μL/min using a Supel-Q PLOT capillary column as an extraction device. The extracted compounds were easily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. The in-tube SPME LC–MS/MS method showed good linearity with correlation coefficients r?≥?0.9998 for TES, CRT, and DHEA using their respective stable isotope-labeled internal standards. The intra-day and inter-day precisions (relative standard deviations) were below 4.9 and 8.5 % (n?=?5), respectively. This method was successfully utilized to analyze TES, CRT, and DHEA in saliva samples without any other pretreatment or interference peaks, and the quantification limits (S/N?=?10) of TES, CRT and DHEA were about 0.01, 0.03 and 0.29 ng/mL saliva, respectively. The recoveries of these compounds spiked into saliva samples were each above 94 %. This method was applied to analyze changes in salivary TES, CRT, and DHEA levels resulting from stress and fatigue load.     

A screw-shaped alignment of pyrene using m-calix[3]amide

m-Calix[3]amide bearing three pyrenes (1a) was prepared by the condensation reaction of 3-nonylaminobenzoic acid derivative using Ph₃PCl₂. Pyrenyl groups were found to be aligned in the screw-like fashion by m-calix[3]amide as confirmed by the X-ray crystallography. Aromatic proton signals observed at the up-field region in the ¹H NMR spectrum at low temperature indicated that pyrenyl groups in 1a are aligned in close proximity in THF solution. UV–vis absorption and fluorescence emission spectra did not show marked peak shift nor concentration fluorescence quenching compared with reference compounds implying no significant electronic interaction between pyrenyl groups. These results can be explained by the steric effect of the m-calix[3]amide platform. On the other hand, an excimer emission was observed for m-calix[3]amide having a flexible spacer between pyrene and m-calix[3]amide (1b).     

Total synthesis of PDE-I and -II by copper-mediated double aryl amination

A concise total synthesis of PDE-I and -II featuring copper-mediated double aryl amination with the combination of CuI, CsOAc, and Cs₂CO₃ is described. The highly substituted pyrroloindole skeleton was constructed by a one-pot five-step sequence including double aryl amination, β-elimination, deprotection of a Cbz group, and unexpected formation of an indole via removal of an Ns group followed by rearomatization. The undesired elimination of the protecting group (Ns group) was hampered by using the Boc group as a protecting group in the second-generation synthesis, which excluded the reduction of the indole required in the first-generation synthesis.     

Oxygenation and chlorination of aromatic hydrocarbons with hydrochloric acid photosensitized by 9-mesityl-10-methylacridinium under visible light irradiation

Efficient photocatalytic oxygenation of toluene occurs under visible light irradiation of 9-mesityl-10-methylacridinium (Acr⁺–Mes) in oxygen-saturated acetonitrile containing toluene and aqueous hydrochloric acid with a xenon lamp for 15 h. The oxygenated products, benzoic acid (70 %) and benzaldehyde (30 %), were formed after the photoirradiation. The photocatalytic reaction is initiated by intramolecular photoinduced electron transfer from the mesitylene moiety to the singlet excited state of the Acr⁺ moiety of Acr⁺–Mes, which affords the electron-transfer state, Acr^?–Mes^?+. The Mes^?+ moiety can oxidize chloride ion (Cl^?) by electron transfer to produce chlorine radical (Cl^?), whereas the Acr^? moiety can reduce O₂ to O ₂ ^?? . The Cl^? radical produced abstracts a hydrogen from toluene to afford benzyl radical in competition with the bimolecular radical coupling of Cl^?. The benzyl radical reacts with O₂ rapidly to afford the peroxyl radical, leading to the oxygenated product, benzaldehyde. Benzaldehyde is readily further photooxygenated to yield benzoic acid with Acr^?–Mes^?+. In the case of an aromatic compound with electron-donating substituents, 1,3,5-trimethoxybenzene, photocatalytic chlorination occurred efficiently under the same photoirradiation conditions to yield a monochloro-substituted compound, 2,4,6-trimethoxychlorobenzene.     

Reduction Reaction of the Copper(II) Complex Bearing 1,3-Di(pyridine-2-carboxaldimino)propane (pitn) by Decamethylferrocene in Acetonitrile

The reduction reaction of the Cu(II)–pitn complex (pitn = 1,3-di(pyridine-2-carboxaldimino)propane) by decamethylferrocene [Fe(Cp*)₂] was examined in acetonitrile. The observed pseudo-first-order rate constants exhibited saturation kinetics with increasing excess amount of [Fe(Cp*)₂]. Detailed analyses revealed that the reaction is controlled by a structural change prior to the electron transfer step, rather than a conventional bimolecular electron transfer process preceded by ion pair (encounter complex) formation. The rate constant for the structural change was estimated to be 275 ± 13 s^?1 at 298 K (?H* = 33.3 ± 1.0 kJ·mol^?1, ?S* = 86 ± 5 J·mol^?1·K^?1), which is the fastest among gated reactions involving CuN₄ complexes. It was confirmed by EPR measurement and Conflex calculations that the dihedral angle between the two N–N planes is significantly large (40°) in solution whereas it is merely 17.14° in the crystal.     

Characterization of flower-inducing compound in Lemna paucicostata exposed to drought stress

A flower-inducing compound, LDS1, was isolated from a free-floating aquatic plant, Lemna paucicostata. The chemical structure and the absolute stereochemistry of LDS1 were determined as (9R,13R,11E,15Z)-9,13-dihydroxy-10-oxooctadeca-11,15-dienoic acid for its most abundant diastereomer. LDS1 was enzymatically produced when the plant was exposed to drought stress, and induced flowering at a concentration of 10 nM.     

Tubular structures bearing channels in organic crystals composed of adamantane-based macrocycles

Five macrocyclic molecules (1–5) were efficiently synthesized from the dimerization and trimerization of di-substituted adamantane derivatives, which were composed of three different aromatic units and two different linker groups. Three single-crystals were obtained from these macrocyclic molecules, including a set of pseudopolymorphs (3a and 3b) of macrocycle 3 and another macrocycle 5 (5a). Single crystal X-ray analysis revealed that the three monocyclic compounds were rectangular or square in shape with solvent molecules in the cavity. Macrocycle 3 in 3a formed stacks to produce tubular structures with channels that assembled into three-dimensional networks through CH/π interactions.     

Adsorption and photochemical behaviors of the novel cationic xanthene derivative on the clay surface

Novel tetra-cationic xanthene derivative (Flu) was synthesized. Its adsorption and photochemical behaviors on the clay surface were investigated. Fluorescence quantum yield (?_f) and fluorescence lifetime were 0.50 and 2.9 ns for Flu/clay complex. ?_f of Flu was enough high (>0.1) even at high density conditions (0.080 molecules nm⁻²). It is supposed that the strong interaction between clay and Flu by the ‘Size-Matching Effect’ realizes the highly emissive clay complexes at high density adsorption condition by a suppression of a molecular aggregation, which tends to decrease the photochemical activity.     

Quantum transport of massless Dirac fermions

Motivated by recent graphene transport experiments, we undertake a numerical study of the conductivity of disordered two-dimensional massless Dirac fermions. Our results reveal distinct differences between the cases of short-range and Coulomb randomly distributed scatterers. We speculate that this behavior is related to the Boltzmann transport theory prediction of dirty-limit behavior for Coulomb scatterers.