A Tri‐µ‐O‐S‐O Manganese Dimer: Synthesis,Structral and EPR Study

A Tri‐µ‐O‐S‐O coordinative manganese dimer: [Mn₂(SO₄)₂(phen)₄]·CH₃OH (phen1,10‐phenanthroline) ( 1 ) was yielded by the reaction of 1,10‐phenanthroline and MnSO₄·H₂O in a mixed solvent of methanol and acetonitrile under room temperature and was structurally characterized. Single crystal analysis shows that complex 1 has polymeric structure based on binuclear Mn(II) units bridged by O‐S‐O groups of two SO₄²⁻ anion. The UV spectrum of the complex clarifies that each metal‐organic building unit parallels with each other through the Π‐Π interactions of face‐to‐face separations of two 1,10‐phen planes among the complex, forming a layered structure. And the electronic paramagnetic resonance (EPR) signal clearly indicates that those manganese atoms in complex 1 are in +2 oxidation states.     

Retention Prediction System of O‐Aryl,O‐(1‐methylthioethylidene‐amino)phosphates on RP‐HPLC

Using factor analysis and stepwise linear regression methods, two parameters – CMR and ECCR – were selected from eight solute‐related structure parameters as the most retention‐influencing parameters. The relationships between the retention data (k ´) and the two structure parameters were established for 13 O‐aryl,O‐(1‐methylthioethylideneamino)phosphate compounds under a wide range of experimental conditions. The retention data (k ´) of another seven compounds with similar structures were predicted using these QSRR equations. Good agreement was obtained between the experimental k ´ values and predicted ones.     

Comparison of Different Di‐tert‐butyldimethyl‐Silylated Cyclodextrins as Chiral Stationary Phases in Capillary Gas Chromatography

Separation factors and thermodynamic data for the separation of various chiral analytes on different di‐O‐tert‐butyldimethyl‐silylated cyclodextrin derivatives are collected and described. Modifying the substitution pattern of the tert‐butyldimethylsilyl group in position 2 and 3 or changing from β‐ to γ‐cyclodextrin significantly affects the separation properties of the cyclodextrin derivatives.     

Generation of Aryl(2‐lithiophenyl)methanone O‐Methyl Oximes and Their Use for the Synthesis of N‐(3‐Alkyl‐1‐aryl‐ or 1,3‐diaryl‐1H‐isoindol‐1‐yl)‐O‐methylhydroxylamines via the Reaction with Nitriles

An efficient two‐step procedure for the preparation of a new type of 1H‐isoindoles, i.e., N‐(3‐alkyl‐1‐aryl‐ or 1,3‐diaryl‐1H‐isoindol‐1‐yl)‐O‐methylhydroxylamines 5 , from readily available aryl(2‐bromophenyl)methanones 1 has been developed. Aryl(2‐bromophenyl)methanone O‐methyloximes 2 , derived from the corresponding ketones, were treated with BuLi in Et₂O at 0° to generate novel lithium compounds, aryl(2‐lithiophenyl)methanone O‐methyloximes 3 , which were allowed to react with nitriles to give the desired products 5 in moderate‐to‐fair yields.     

Total Synthesis of the Biologically Active,Naturally Occurring 3,4‐Dibromo‐5‐[2‐bromo‐3,4‐dihydroxy‐6‐(methoxymethyl)benzyl]benzene‐1,2‐diol and Regioselective O‐Demethylation of Aryl Methyl Ethers

3,4‐Dibromo‐5‐[2‐bromo‐3,4‐dihydroxy‐6‐(methoxymethyl)benzyl]benzene‐1,2‐diol ( 2 ), a natural product, has been synthesized for the first time starting from (3‐bromo‐4,5‐dimethoxyphenyl)methanol ( 5 ) in five steps and with an overall yield of 34%. The reaction of some methoxymethyl‐substituted aryl methyl ethers with BBr₃, followed by the addition of MeOH, afforded the corresponding methoxymethyl‐substituted arylphenols in high yields.     

Biotransformation and metabolic profile of caudatin‐2,6‐dideoxy‐3‐O‐methy‐β‐d‐cymaropyranoside with human intestinal microflora by liquid chromatography quadrupole time‐of‐flight mass spectrometry

In our previous studies, caudatin‐2,6‐dideoxy‐3‐O‐methy‐β‐d‐ cymaropyranoside (CDMC) was for the first time isolated from Cynanchum auriculatum Royle ex Wightand and was reported to possess a wide range of biological activities. However, the routes and metabolites of CDMC produced by intestinal bacteria are not well understood. In this study, ultra‐performance liquid chromatography/quadrupole time‐of‐flight mass spectrometry (UPLC‐Q‐TOF‐MS) technique combined with Metabolynx^TMsoftware was applied to analyze metabolites of CDMC by human intestinal bacteria. The incubated samples collected for 48 h in an anaerobic incubator and extracted with ethyl acetate were analyzed by UPLC‐Q‐TOF‐MS within 12 min. Eight metabolites were identified based on MS and MS/MS data. The results indicated that hydrolysis, hydrogenation, demethylation and hydroxylation were the major metabolic pathways of CDMC in vitro. Seven strains of bacteria including Bacillus sp. 46, Enterococcus sp. 30 and sp. 45, Escherichia sp. 49A, sp. 64, sp. 68 and sp. 75 were further identified using 16S rRNA gene sequencing owing to their relatively strong metabolic capacity toward CDMC. The present study provides important information about metabolic routes of CDMC and the roles of different intestinal bacteria in the metabolism of CDMC. Moreover, those metabolites might influence the biological effect of CDMC in vivo, which affects the clinical effects of this medicinal plant. Copyright © 2015 John Wiley & Sons, Ltd.     

Improved Synthesis of Phytosphingosine and Dihydrosphingosine from 3,4,6‐Tri‐O‐benzyl‐D‐galactal

An efficient and facile synthesis of phytosphingosine and dihydrosphingosine derivatives is described with less steps and in improved overall yield (66–72%) starting from commercially available tri‐O‐benzyl‐D ‐galactal. The key steps include Wittig reaction, Mitsunobu transformation, reduction, and deprotection.     

A rapid and sensitive LC–MS/MS method for quantification of quercetin‐3‐O‐β‐d‐glucopyranosyl‐7‐O‐β‐d‐gentiobioside in plasma and its application to a pharmacokinetic study

A rapid and sensitive LC–MS/MS method with good accuracy and precision was developed and validated for the pharmacokinetic study of quercetin‐3‐O‐β‐d ‐glucopyranosyl‐7‐O‐β‐d ‐gentiobioside (QGG) in Sprague–Dawley rats. Plasma samples were simply precipitated by methanol and then analyzed by LC–MS/MS. A Venusil® ASB C₁₈ column (2.1 × 50 mm, i.d. 5 μm) was used for separation, with methanol–water (50:50, v/v) as the mobile phase at a flow rate of 300 μL/min. The optimized mass transition ion‐pairs (m/z) for quantitation were 787.3/301.3 for QGG, and 725.3/293.3 for internal standard. The linear range was 7.32–1830 ng/mL with an average correlation coefficient of 0.9992, and the limit of quantification was 7.32 ng/mL. The intra‐ and inter‐day precision and accuracy were less than ±15%. At low, medium and high quality control concentrations, the recovery and matrix effect of the analyte and IS were in the range of 89.06–92.43 and 88.58–97.62%, respectively. The method was applied for the pharmacokinetic study of QGG in Sprague–Dawley rats. Copyright © 2016 John Wiley & Sons, Ltd.     

MALDI‐MS profiling of serum O‐glycosylation and N‐glycosylation in COG5‐CDG

Congenital disorders of glycosylation (CDG) are due to defective glycosylation of glycoconjugates. Conserved oligomeric Golgi (COG)‐CDG are genetic diseases due to defects of the COG complex subunits 1–8 causing N‐glycan and O‐glycan processing abnormalities. In COG‐CDG, isoelectric focusing separation of undersialylated glycoforms of serum transferrin and apolipoprotein C‐III (apoC‐III) allows to detect N‐glycosylation and O‐glycosylation defects, respectively. COG5‐CDG (COG5 subunit deficiency) is a multisystem disease with dysmorphic features, intellectual disability of variable degree, seizures, acquired microcephaly, sensory defects and autistic behavior. We applied matrix‐assisted laser desorption/ionization‐MS for a high‐throughput screening of differential serum O‐glycoform and N‐ glycoform in five patients with COG5‐CDG. When compared with age‐matched controls, COG5‐CDG showed a significant increase of apoC‐III_0a (aglycosylated glycoform), whereas apoC‐III₁ (mono‐sialylated glycoform) decreased significantly. Serum N‐glycome of COG5‐CDG patients was characterized by the relative abundance of undersialylated and undergalactosylated biantennary and triantennary glycans as well as slight increase of high‐mannose structures and hybrid glycans. Using advanced and well‐established MS‐based approaches, the present findings reveal novel aspects on O‐glycan and N‐glycan profiling in COG5‐CDG patients, thus providing an increase of current knowledge on glycosylation defects caused by impairment of COG subunits, in support of clinical diagnosis. Copyright © 2017 John Wiley & Sons, Ltd.