Direct synthesis of plasmenylcholine from allyl-substituted glycerols

We report a new method for the facile preparation of plasmenylcholine via reaction of lithioalkoxy allyl intermediates with 1-iodoalkanes as the key step in the stereoselective formation of 1'-(Z)-alkenyl glyceryl ethers. The allyl anion intermediate is prepared by treating mono- or disiloxy-protected 1-allylglycerol precursors with s-BuLi at -65 to -80 degrees C. Subsequent addition of 1-iodoalkane solutions at low temperature gives moderate yields of gamma-coupled, Z-vinyl ethers as the major product and alpha-coupled product as the minor component. Several different preparative strategies for the total synthesis of plasmalogens are enabled by this simple transformation.     

机械活化木薯淀粉氧化产物的结构表征

采用搅拌球磨机对木薯淀粉进行机械活化,以活化60min的木薯淀粉为原料,CuSO4为催化剂,H2O2为氧化剂干法制备氧化淀粉。利用红外光谱、扫描电子显微镜、X-射线衍射等手段对产物的结构进行表征分析,并与原淀粉的氧化产物进行比较。结果表明,机械活化对木薯淀粉的氧化反应有显著的影响。原木薯淀粉的氧化反应主要发生在淀粉颗粒的表面及无定形区,部分发生在结晶区,产物是无定形及结晶状态的结构;活化淀粉的氧化反应在淀粉团粒表面及内部均匀进行,产物是无定形的聚集状态结构。并就机械活化对淀粉氧化的强化机理进行了探讨。     

Structural characterization of forced degradation products of empagliflozin by high resolution mass spectrometry

Eleven unique degradation products (DPs) of empagliflozin (EGF), a sodium glucose cotransporter (SGLT) 2 inhibitor have been reported for the first time. These DPs were generated as per International Conference on Harmonization (ICH) guidelines Q1 (R2) using stress conditions such as acid, base hydrolysis and oxidative environment. The sum of 12 DPs have been successfully resolved by Ultra-High Performance Liquid Chromatography-Mass Spectrometry (UHPLC-MS) method involving Eclipse plus C₁₈ RRHD (2.1?×?50?mm, 1.8µm) column and mobile phase comprising of water with 0.1% formic acid and methanol in 1:1 quotient. Structure of DPs and the degradation pathways have been proposed on the basis of accurate mass and MS/MS fragmentation pattern acquired through Liquid Chromatography-Electrospray Ionization Quadrupole Time of Flight Mass Spectrometer (LC-ESI-QTOF-MS). It has been observed that maximum DPs were formed during acid hydrolysis and the major ones were (2S,3R,4R,5S,6R)-2-(4-chloro-3-(4-(((S)-1,4-dihydroxybutan-2-yl)oxy)benzyl)phenyl)-6-(hydroxymethyl)tetrahydro-2H-pyran-3,4,5-triol (DP1) and (2S,3R,4R,5S,6R)-2-(4-chloro-3-(4-hydroxybenzyl)phenyl)-6-(hydroxymethyl) tetrahydro-2H-pyran-3,4,5-triol (DP2) generated due to ring opening of tetrahydrofuran moiety and elimination of tetrahydrofuran ring respectively. The proposed structures of DPs and their associated pathways will be essential for optimization of manufacturing and quality control parameters of EGF.     

Systemic suppression of the contact hypersensitivity by the products of protoporphyrin IX photooxidation

Photodynamic therapy (PDT) is frequently accompanied by induction of systemic immunosuppression. Photochemical mechanisms underlying this effect are not completely understood. Here, we demonstrate the immunosuppressive activity of photooxidation products of protoporphyrin IX dimethyl ester (PPIX) in a murine model of contact hypersensitivity (CHS) to 2,4-dinitrofluorobenzene (DNFB). Intravenous injection of the preirradiated solution of PPIX to mice resulted in fluence-dependent suppression of the CHS. The samples of photodecomposed PPIX with suppressive effect on the CHS contained chlorin-type products, namely, two isomers of photoprotoporphyrin (pPP1 and pPP2) as main photoproducts. Concentration-dependent suppression of the CHS was also induced when purified pPP1 or pPP2 were injected to mice intravenously. These purified photoproducts exerted equal immunosuppressive activity. The highest suppression of the CHS was induced when pPP1 was injected 20 h before sensitization with DNFB. The lowest suppression was at its injection time 24 h before challenge. The pPP1-induced suppression of the CHS was adoptively transferable and was associated with generation of cells with suppressive functions. These suppressor cells inhibited the efferent phase of the CHS. Our results strongly indicate that induction of systemic immunosuppression by PDT with PPIX may proceed through photobleaching of photosensitizer and generation of photoprotoporphyrins, which can affect T cell immunity.     

Direct detection of isoprene photooxidation products by using synchrotron radiation photoionization mass spectrometry

We report the combination of a vacuum ultraviolet photoionization mass spectrometer, operating on the basis of synchrotron radiation, with an environmental reaction smog chamber for the first time. The gas- and pseudo-particle-phase products of OH-initiated isoprene photooxidation reactions were measured on-line and off-line, respectively, by mass spectrometry. It was observed that aldehydes, methacrolein, methyl vinyl ketone, methelglyoxal, formic acid, and similar compounds are the predominant gas-phase photooxidation products, whereas some multifunctional carbonyls and acids mainly exist in the particle phase. This finding is reasonably consistent with results of studies conducted in other laboratories using different methods. The results indicate that synchrotron radiation photoionization mass spectrometry coupled with a smog chamber is a potentially powerful tool for the study of the mechanism of atmospheric oxidations and the formation of secondary organic aerosols.     

Structural and spectroscopic characterization of the dirhenium acetamidate products resulting from the hydrolysis of acetonitrile

Unsaturated molecules such as nitriles are activated upon coordination to a dirhenium core. Acetonitrile is hydrolyzed in the presence of water to produce coordinated bridging acetamidate ligands as demonstrated by the reaction of [N(C₄H₉)₄]₂[Re₂Cl₈] with CH₃CN and water in ethanol to form the acetamidate complexes, [N(C₄H₉)₄][Re₂Cl₅(μ-CH₃C(O)NH)(μ-CH₃C(OH)N)]·3CH₂Cl₂ [I] and Re₂Cl₄(μ-CH₃C(O)NH)(μ-dppm)₂·4 CH₂Cl₂/0.833 EtOH [II]. Compound II is formed when I is reduced upon coordination of bis(diphenylphosphino)methane (dppm). Compounds I and II were characterized using X-ray crystallography and a variety of other spectroscopic methods.     

Single-run analysis of retinal isomers, retinol and photooxidation products by high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) procedure was developed to allow the rapid separation, in a single run, of a mixture of the main retinal isomers (all-trans, 13-cis, 9-cis), all-trans-retinol, and of the two major photooxygenated photoproducts (5,8-peroxyretinal and 5,6-epoxyretinal). The mixture was separated by HPLC on an octadecyl (ODS) column with 16% (v/v) diethyl ether in hexane as mobile phase and anthracene as the internal standard. A commercial type cosmetic formulation containing 0.05% all-trans-retinal was analyzed successfully for this analyte.     

Structural characterization of magnetoferritin

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Structural investigation of parvifolinone transformation products

The structures of the transformation products of parvifolinone, trans-2,3-dihydro-3,6-dimethyl-7-acetoxy-2-carboxymethylenebenzopyran-4-one and 5-methyl-6-(2′,4′-diacetoxy-5-methylphenyl)pyran-2-one, are proved by X-ray methods. The conformation of the dihydropyran-4-one moiety in the former is a distorted half-chair. The pyran-2-one ring in the latter is planar. Instituto Tecnologico de Morelia, Av. Tecnologico 15000, Morelia Mich., Mexico; Instituto de Investigaciones Quimico-Biologicas, Universidad Michoacana, Cd. Universitaria Edif. B-I, Morelia Mich., Mexico; A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow 117813, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 498–505, April, 1999.     

Structural characterization of ZnLiNbO4

The structure of ZnLiNbO₄ crystals grown directly from the stoichiometric melt by the Laser Heated Pedestal Growth technique has been determined by X-ray diffraction. ZnLiNbO₄ crystallizes in the space group P4₁22 (n^o 91) with a=6.0818(9) Å c=8.3818(17) Å and Z=4. The crystal structure is that of an ordered type of a tetragonal spinel with Nb and Li ions in octahedral environment and Zn ions in tetrahedral position.     

光氧化反应的研究VII. 赤霉酸甲酯的单线态氧反应

本文初次探讨赤霉酸甲酯的敏化光氧化反应规律及其在合成应用上的可能性。     

Dye-sensitized photooxidation of chlorpromazine

Chlorpromazine efficently quenches singlet oxygen (¹O₂) with a k_q = 3.5 × 10⁷ M^?1 s^?1. The major result of the chemical interaction between these two species is the cleavage of the N-side chain.     

Solid-state characterization of glyburide-cyclodextrin co-ground products

Natural crystalline (α-, β-, γ-) and amorphous derivative (hydroxypropyl-β- and methyl-β) cyclodextrins were selected as potential carriers for obtaining, through a co-grinding technique, a stable activated amorphous form of glyburide with improved dissolution properties. Differential scanning calorimetry (DSC) was used to investigate solid-state modifications of the drug induced by co-grinding with the selected carriers in a high energy vibrational micro-mill. X-ray powder diffraction and FTIR spectroscopy were employed as additional techniques to support DSC data. Equimolar drug : cyclodextrin physical mixtures were co-ground for different times (up to 60 min) at constant vibration frequency (24 Hz). A progressive drug amorphization with increasing grinding time was observed in all binary systems, but, interestingly, different degrees of sensitivity to the mechanical-chemical activation were evident. In fact, blends with natural cyclodextrins, despite the initial higher crystallinity than those with the amorphous derivatives, required the same or shorter co-grinding times (60 min) to achieve complete drug amorphization. Stability studies indicated no appreciable drug recrystallization in co-ground products after 4 months storage in sealed containers at 25°C or 1 month at 25°C and 75% RH. No stability differences were detected between products with natural or derivative cyclodextrins. The results accounted for the suitability of cyclodextrin co-grinding technique to obtain and stabilize glyburide in the activated amorphous form. This revised version was published online in July 2006 with corrections to the Cover Date.     

Structural diversity of peroxidase-catalyzed oxidation products of o-methoxyphenols

[reaction: see text] The biocatalytic oxidation of o-methoxyphenolic compounds led to a variety of oligophenols (dimers to pentamers) and some of their oxidation products. The reaction was carried out in an aqueous medium at room temperature with hydrogen peroxide as the terminal oxidant in a facile and green route to potentially bioactive compounds. Detailed structural information on the products of peroxidase-catalyzed oxidation of o-methoxyphenols is presented for the first time.     

Structural characterization of electrochemically and in vitro biologically generated oxidation products of atorvastatin using UHPLC/MS/MS

Ultrahigh-performance liquid chromatography coupled with high-mass-accuracy tandem mass spectrometry (UHPLC–MS–MS) has been used for elucidation of the structures of oxidation products of atorvastatin (AT), one of the most popular commercially available drugs. The purpose of the study was identification of AT metabolites in rat hepatocytes and comparison with electrochemically generated oxidation products. AT was incubated with rat hepatocytes for 24 h. Electrochemical oxidation of AT was performed by use of a three-electrode off-line system with a glassy carbon working electrode. Three supporting electrolytes (0.1 mol L^?1 H₂SO₄, 0.1 mol L^?1 HCl, and 0.1 mol L^?1 NaCl) were tested, and dependence on pH was also investigated. AT undergoes oxidation by a single irreversible process at approximately +1.0 V vs. Ag/AgCl electrode. The results obtained revealed a simple and relatively fast way of determining the type of oxidation and its position, on the basis of characteristic neutral losses (NLs) and fragment ions. Unfortunately, different products were obtained by electrochemical oxidation and biotransformation of AT. High-mass-accuracy measurement combined with different UHPLC–MS–MS scans, for example reconstructed ion-current chromatograms, constant neutral loss chromatograms, or exact mass filtering, enable rapid identification of drug-related compounds. β-Oxidation, aromatic hydroxylation of the phenylaminocarbonyl group, sulfation, AT lactone and glycol formation were observed in rat biotransformation samples. In contrast, a variety of oxidation reactions on the conjugated skeleton of isopropyl substituent of AT were identified as products of electrolysis.