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.     

Site-specific C content by quantitative isotopic C Nuclear Magnetic Resonance spectrometry: A pilot inter-laboratory study

Isotopic ¹³C NMR spectrometry, which is able to measure intra-molecular ¹³C composition, is of emerging demand because of the new information provided by the ¹³C site-specific content of a given molecule. A systematic evaluation of instrumental behaviour is of importance to envisage isotopic ¹³C NMR as a routine tool. This paper describes the first collaborative study of intra-molecular ¹³C composition by NMR. The main goals of the ring test were to establish intra- and inter-variability of the spectrometer response. Eight instruments with different configuration were retained for the exercise on the basis of a qualification test. Reproducibility at the natural abundance of isotopic ¹³C NMR was then assessed on vanillin from three different origins associated with specific δ¹³C_i profiles. The standard deviation was, on average, between 0.9 and 1.2‰ for intra-variability. The highest standard deviation for inter-variability was 2.1‰. This is significantly higher than the internal precision but could be considered good in respect of a first ring test on a new analytical method. The standard deviation of δ¹³C_i in vanillin was not homogeneous over the eight carbons, with no trend either for the carbon position or for the configuration of the spectrometer. However, since the repeatability for each instrument was satisfactory, correction factors for each carbon in vanillin could be calculated to harmonize the results.     

Convenient Method for Dehalogenation of Aryl Halides

Reductive dehalogenation of aryl halides was achieved using hydrogen and a palladium catalyst. By using deuterium gas, the deuterated arenes were readily prepared.     

Synthetic Studies on Sialoglycoconjugates 60: α-Stereocontrolled,Glycoside Synthesis of Trimeric Sialic Acid with Galactose and Lactose Derivatives

Abstract

α-Stereocontrolled, glycoside synthesis of trimeric sialic acid is described toward a systematic approach to the synthesis of sialoglycoconjugates containing an α-sialyl-(2→8)-α-sialyl-(2→8)-sialic acid unit α-glycosidically linked to O-3 of a galactose residue in their oligosaccharide chains. Glycosylation of 2-(trimethylsilyl)ethyl 6-O-benzoyl-β-d-galactopyranoside (4) or 2-(trimethylsilyl)ethyl 2,3,6,2′,6′-penta-O-benzyl-β-lactoside (5), with methyl [phenyl 5-acetamido-8-O-[5-acetamido-8-O-(5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-d-glycero-α-d-galacto-2-nonulopyranosylono-1”, 9′-lactone)-4,7-di-O-acetyl-3,5-dideoxy-d-glycero-α-d-galacto-2-nonulopyranosylono-1′, 9-lactone]-4,7-di-O-acetyl-3,5-dideoxy-2-thio-d-glycero-d-galacto-2-nonulopyranosid]onate (3), using N-iodosuccinimide-trifluoromethanesulfonic acid as a promoter, gave the corresponding α-glycosides 6 and 8, respectively. The glycosyl donor 3 was prepared from trimeric sialic acid by treatment with Amberlite IR-120 (H⁺) resin in methanol, O-acetylation, and subsequent replacement of the anomeric acetoxy group with phenylthio. Compounds 6 and 8 were converted into the per-O-acyl derivatives 7 and 9, respectively.     

Synthetic Studies on Sialoglycoconjugates 70: Synthesis of Sialyl and Sulfo Lewis × Analogs Containing a Ceramide or 2-(Tetradecyl)hexadecyl Residue

Abstract

Four sialyl and sulfo Le^x analogs containing glucose in place of N-acetylglucosamine, and a ceramide or 2-(tetradecyl)hexadecyl residue, have been synthesized. Condensation of O-(methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-d-glycero-α-d-galacto-2-nonulopyranosylonate)-(2→3)-O-(4-O-acetyl-2,6-diO-benzoyl-β-d-galactopyranosyl)-(1→4)-O-[(2,3,4-tri-O-acetyl-α-L-fucopyranosyl)-(1→3)]-2,4-di-O-benzoyl-α-d-glucopyranosyl trichloroacetimidate (1) with (2S,3R,4E)-2-azido-3-O-benzoyl-4-octadecene-1,3, diol (2) or 2-(tetradecyl)-hexadecyl-1-ol (3) gave the corresponding β-glycosides 4 and 7. Compound 4 was converted into the ganglioside 6 via selective reduction of the azido group, coupling with octadecanoic acid, O-deacylation, and saponification of the methyl ester group. Hydrolysis of the O-acyl groups in 7 followed by saponification of the methyl ester, gave sialyl Le^x ganglioside analog 8 containing a branched fatty alkyl residue. On the other hand, glycosylation of O-(4-O-acetyl-2,6-di-O-benzoyl-3-O-levulinyl-β-d-galactopyranosyl)-(1→4)-[O-(2,3,4-tri-O-acetyl-α-L-fucopyranosyl)-(1→3)]-2,6-di-O-benzoyl-α-d-glucopyranosyl trichloroacetimidate (13), prepared from 2-(trimethylsilyl)ethyl O-(2,6-di-O-benzoyl-β-d-galactopyranosyl)-(1→4)-O-[(2,3,4-tri-O-benzyl-α-L-fucopyranosyl)-(1→3)]-2,6-di-O-benzoyl-β-d-glucopyranoside (9) via selective 3-O-levulinylation, acetylation, removal of the 2-(trimethylsilyl)ethyl group, with 2 or 3, gave the desired β-glycosides 14 and 19. Selective reduction of the axido group in 14 followed by coupling with octadecanoic acid gave the ceramide derivative 16. Removal of the levulinyl group in 16 and 19, treatment with sulfur trioxide pyridine complex and subsequent hydrolysis of the protecting groups yielded the corresponding sulfo Le^x analogs 18 and 21.     

Synthetic Studies on Sialoglycoconjugates 12: Total Synthesis of Sialyl Neolactotetraosyl Ceramide

Abstract

Sialoglycoconjugates such as glycoproteins and glycolipids are present as components of cell memberanes and play important roles^1,2 in biological systems. Sialyl neolactotetrasyl ceramide (IV³NeuAcnLc₄Cer), a complex type of ganglioside, was isolated as the major ganglioside of human erythrocytes³ and was shown to be a receptor of that this glycolipid induces granulocytic differentiation of human premyelocytic leukemia cell.     

A p‐Quinodimethane‐Bridged Porphyrin Dimer

A p‐quinodimethane (p‐QDM)‐bridged porphyrin dimer 1 has been prepared for the first time. An unexpected Michael addition reaction took place when we attempted to synthesize compound 1 by reaction of the cross‐conjugated keto‐linked porphyrin dimers 8 a and 8 b with alkynyl/aryl Grignard reagents. Alternatively, compound 1 could be successfully prepared by intramolecular Friedel–Crafts alkylation of the diol‐linked porphyrin dimer 14 with concomitant oxidation in air. Compound 1 shows intense one‐photon absorption (OPA, λ_max=955 nm, ε=45400 M ^?1 cm^?1) and a large two‐photon absorption (TPA) cross‐section (σ⁽²⁾_max=2080 GM at 1800 nm) in the near‐infrared (NIR) region due to its extended π‐conjugation and quinoidal character. It also exhibits a short singlet excited‐state lifetime of 25 ps. The cyclic voltammogram of 1 displays multiple redox waves with a small electrochemical energy gap of 0.86 eV. The ground‐state geometry, electronic structure, and optical properties of 1 have been further studied by density functional theory (DFT) calculations and compared with those of the keto‐linked dimer 8 b . This research has revealed that incorporation of a p‐QDM unit into the porphyrin framework had a significant impact on its optical and electronic properties, leading to a novel NIR OPA and TPA chromophore.     

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.