Nitration in the carbazole series

Nitration of9-tosylcarbazole in acetic anhydride solution gives l-nitro (28%), 2-nitro (19%) and 3-nitro (53%) derivatives. The mixture of the nitro compounds obtained from 9-acetylcarbazole contains 10%, 48% and 42% of the isomers, respectively. Under similar conditions 9-nitrosocarbazole shows a different isomer distribution: 34% of 1-nitro and 66% of 3-nitrocarbazole. Nitration of carbazole is a two step process involving formation and rearrangement of 9-nitrocarbazole. The hypothesis was supported by the results of 1,3,6,8-tetrachlorocarbazole nitration and oxidation of 9-nitrosocarbazole and rearrangement of 9-nitrocarbazole in the nitration conditions.     

四环二萜的合成研究 5.对映贝壳杉-16-烯-19酸的合成

本文报道了一条从易得的甜叶菊苷出发经二次骨架重排合成了对映贝壳杉-16-烯-19-酸及其异构体.从甜叶菊苷合成对映贝壳杉-16-烯-19-酸的九步反应总产率为9%而合成对映贝壳杉-15-烯-19-酸的九步反应总产率炒17%.     

On-line monitoring of nine haloacetic acid species at the μg L level using post-column reaction-ion chromatography with nicotinamide fluorescence

A laboratory-built automated instrument is reported for on-line, near real-time monitoring of nine haloacetic acids species (HAA9) in drinking water. The device uses anion-exchange chromatography to separate the HAA9 species, followed by post-column reaction with nicotinamide in basic solution with fluorescence detection. Method detection limits for HAA9 species ranged from 0.6 to 10.1 μg L⁻¹, mean % recovery values ranged from 58 to 161%, and % relative standard deviation ranged from 3.5 to 32% while operating within a factor of 2.5-5 of the method detection limit. The bias between the proposed method and United States Environmental Protection Agency Method 552.3 was measured during two separate on-line studies and using grab samples collected from different distribution systems. In general, the two methods showed good agreement with biases for HAA9 of less than 10 μg L⁻¹.     

导数恒基体强度同步荧光分析法同时测定光谱严重重叠的1-氯蒽和9-溴蒽

通过选择适合测定路径,应用恒基体强度同步及荧光法同时测定了两种光谱严重重叠的蒽衍生物1－氯蒽和9－溴蒽。混合物中1－氯蒽和9－溴蒽不必预分离就能直接同时测定。在混合物中1－氯蒽和9－溴蒽的回收率分别为83．5％－94．0％,90．0％－94．0％,检出限分别为0．69μg/L,10μg/L。     

Acridone-Based Host Materials for Green Phosphorescent and Thermally Activated Delayed Fluorescent OLEDs with Low-Efficiency Roll-Offs

By linking the carbazole unit to the nitrogen atom of acridone through phenyl or pyridyl, two compounds, named 10-(4-(9H-carbazol-9-yl)phenyl)acridin-9(10H)-one (AC-Ph-Cz) and 10-(5-(9H-carbazol-9-yl)pyridin-2-yl)acridin-9(10H)-one (AC-Py-Cz) were designed and synthesized. These two materials, characterized with highly twisted and rigid structure, good thermal stability, and balanced carrier-transporting properties, were employed as host materials for green phosphorescent and thermally activated delayed fluorescent organic light-emitting diodes (OLEDs). The carbazole group, despite its small contribution to the highest occupied molecular orbitals (HOMOs) of these two materials, plays an essential role as an intramolecular host in energy delivering and improving the hole transporting ability of these two hosts. The incorporation of the electron-deficient pyridyl group as a linking group slightly improves the electron transporting capability of AC-Py-Cz. The green phosphorescent OLED (PhOLED) based on AC-Py-Cz exhibited excellent device performance with a turn-on voltage of 2.5 V, a maximum power efficiency and an external quantum efficiency (η_ext) of 89.8 lm W⁻¹ and 25.2 %, respectively, benefitting from the better charge-balancing ability of AC-Py-Cz host due to the presence of the pyridyl bridge. More importantly, all the devices based on these two hosts showed low efficiency roll-off at high brightness due to the suppressed non-radiative transition in the emitting layer. In particular, the AC-Py-Cz-hosted green PhOLED exhibited an efficiency roll-off of 1.6 % from the maximum next at a high brightness of 1000 cd m⁻² and a roll-off of 15.9 % at an extremely high brightness of 10000 cd m⁻². This study manifests that acridone-based host materials have great potential in fabricating OLEDs with low efficiency roll-off.     

The influence of matrix concentration and solvent composition on the results of MALDI MSI,with the aid of wet-interface matrix deposition

Imaging mass spectrometry is a powerful technique for the molecular analysis of tissue sections. As in many analytical methods, sample preparation is one of the main and most important steps to obtain results of good quality. Usually, the matrix concentration and solvent composition in different studies are taken for granted without any further consideration. In our studies, we aimed to find how matrix concentration and a type of solvent influence the signal. Moreover, we also aimed to find the relationship between these parameters, how they influence the spectra, and how they influence obtained ion maps. In our experiments, we used SunCollect®, which is a commercially available wet-interface system for matrix deposition. We decided to choose two matrix concentrations (2,5-dihydroxybenzoic acid [DHB]: 15 and 25 mg/mL; 9-aminoacridine [9AA]: 7 and 5 mg/mL) and two different water solutions of solvents in two different percentages for the matrices (DHB: 50% and 70% of methanol [MeOH] and acetonitrile [ACN]; 9AA 70% and 50% of ethanol [EtOH] and MeOH). In the end, the influence of these parameters on obtained spectra and ion maps was assessed.     

THE GECKO OPSIN: RESPONSES TO GEOMETRIC ISOMERS OF RETINAL and 3-DEHYDRORETINAL

Abstract— The opsin of the visual pigment (P521) of the Tokay gecko rapidly regenerates four spectrally different photopigments with the 9-cis and 11-cis isomers of both the vitamin A,- and A₂-aldehydes. The opsin displays the classic stereospecificity for both A₁- and A₂-series of isomers. The two photopigments regenerated with 9-cis- and ll-cw-3-dehydroretinals respond to chloride and nitrate ions as do the comparable pigments formed with 9-cis- and 11-ris-retinal. The result is a family of pigments absorbing with spectral maxima ranging from 464 to 540 nm, a span of some 3000 cm^-1. The photosensitivity of all four pigments was determined and found to be in relative order: 100% (11-cis-A₂), 77% (11- cis -A₂), 36% (9- cis -A,) and 14% (9- cis -A₂).     

Novel synthesis of (−)-trans-Δ9,11-tetrahydrocannabinol

Addition of hydrogen chloride gas to a solution of Δ⁸-tetrahydrocannabinol in dry dichloromethane at -60° in the presence of zinc chloride results in the formation of a higher concentration of 9-α-chlorohexa-hydrocannabinol (75%) than the thermodynamically more stable 9-β-chlorohexahydrocannabinol (25%). The two isomers can be separated by reverse-phase hplc. Elimination of hydrogen chloride from 9-α-chlorohexa-hydrocannabinol using potassium t-amylate under anhydrous conditions gives exclusively Δ^9,11-tetrahydrocannabinol in overall yield of 65%.     

Enantioselective total synthesis of quadrigemine C and psycholeine

The first total syntheses of higher-order members of the polypyrrolidinoindoline alkaloid family are reported. The synthesis of quadrigemine C (1) and psycholeine (3) begins with synthetic meso-chimonanthine (4), which is synthesized from commercially available oxindole and isatin in 13 steps and 35% overall yield. Double Stille cross coupling of diiodide 7, available in three steps from 4, with vinylstannane 8 produces dibutenanilide 9. Double catalytic asymmetric Heck cyclization of 9 simultaneously installs the two peripheral quaternary stereocenters and desymmetrizes this advanced meso precursor to deliver the chiral, decacyclic intermediate 11 in 62% yield and 90% ee. In two additional steps, 11 is converted to 1, which upon treatment with acid generates 3. The synthesis of quadrigemine C (1), which rigorously confirms its relative and absolute configuration, was executed in 19 linear steps (2% overall yield) from commercially available starting materials.     

An Improved Synthesis of Laminin Fragment CR9

Laminin nonapeptide CR9 was synthesized via two different methods.A notably enhanced yicld(46.8%)was obtained from method B compared to that(12.4%)from standard protocol(method A).     

Synthesis of the C-13 side chain precursors of the 9-dihydrotaxane analogue ABT-271

N-Boc-L-Leucinol was converted to two C-13 side chain precursors of the 9-dihydrotaxane analogue ABT-271. The trans-oxazolidine acid 4 and the cis-Boc-lactam 2b were prepared in 44% and 40% overall yield, respectively, and with excellent (>98%) stereochemical purity.     

Synthesis and tautomerism of ethyl 2-(2-benzothiazolyl)-2-(6-purinyl)acetate and related compounds

Reaction of 6-chloro-9H-(2-tetrahydropyranyl)purine ( 2d ) with the sodium salt of ethyl benzothiazole-2-ace-tate ( 1 ) in dimethylformamide effects condensation of the two compounds (with loss of sodium chloride) to give the corresponding ethyl diarylacetate 4 (35%), present largely as an enol chelate tautomer. Isolated as a by-product is 6-(2-aminophenyl-1-thio)-9H-(2-tetrahydropyranyl)-purine (4%), formed via opening of the thiazole ring. Removal of the tetrahydropyranyl protective group from 4 occurs by treatment with p-toluenesulfonic acid in aqueous ethanol to produce ethyl benzothiazole-2-(6-purinyl)acetate (80%), existent largely as two enol chelate isomers. Spectral data for the various products are presented. An attempt to use 6-chloro-9-acetyl-9H-purine in place of 2d in the first reaction gives acetylation of 1 instead of condensation.     

Comparison of an instrumental and modified Kjeldahl technique for determination of nitrogen in niobium and tantalum alloys

Results obtained for the determination of nitrogen in two tantalum alloys and six niobium alloys by modified Kjeldahl and Leco TC-30 nitrogen—oxygen determinator are compared. In the 5–25 ppm range, for tantalum alloys, the relative standard deviation was 3–9% by the Kjeldahl procedure and 9–11% by the instrumental technique. In the range 30–80 ppm, for niobium alloys, the relative standard deviation was 2–8% by the Kjeldahl procedure and 5–7% by the instrumental technique.     

Effects of Different Eelectron-withdrawing Moieties on the General Photoelectric Properties of Fluorene-based Dimers

Here, 9,9,9'-tris(4-butoxyphenyl)-9H-9'H-2,2'-difluorene(DF) was synthesized as a reference for compa-rison, and diphenyl sulfone and triphenylphosphine oxygen were introduced to the 9-position of fluorene through a C-H coupling reaction to produce two fluorene-based oligomers 9',9'-[sulfonylbis(4,1-phenylene)]bis[9,9,9'-tris-(4-butoxyphenyl)-9H,9'H-2,2'-bifluorene](DF)₂SO₂ and phenylbis(4-{9,9',9'-tris(4-butoxyphenyl)-9H,9'H-[2,2'-bif-luorene]-9-yl}phenyl)phosphine oxide[(DF)₂PO]. Solid powders of all the three compounds exhibit excellent thermal stability with thermal temperature at 5% mass loss of 375, 429 and 383℃ for (DF)₂SO₂, (DF)₂PO and DF. In addition, owing to the distorted molecular structure and weak electron-absorbing ability of the acceptor, (DF)₂SO₂ and (DF)₂PO do not have obvious intramolecular charge transfer characteristics, and exhibit stable localized 394 nm/375 nm fluorescence emission peaks in different polar solvents. The absolute luminescence quantum efficiencies of (DF)₂SO₂, (DF)₂PO and DF solid powders are 20.83%, 10.03% and 59.46%. Compound DF has the highest quantum yield as an electron donor. The chromaticity coordinates of the blue OLED devices based on DF and DF₂SO₂ fabricated by solution spin coating were (0.19, 0.10) and (0.19, 0.11), which were closest to the deep blue region, and the corresponding maximum external quantum efficiencies are 1.45% and 0.87%, respectively, which are higher than that of (DF)₂PO(0.25%) and consistent with the difference in the solid-state quantum efficiency between them.     

Rapid and practical synthesis of (-)-1-deoxyaltronojirimycin

Herein a practical and scalable route to 1-deoxyaltronojirimycin is presented. The target is achieved in 9 steps and 43% yield featuring only two chromatographic purifications.     

Monolayer dispersion of NiO in NiO/Al2O3 catalysts probed by positronium atom

NiO/Al(2)O(3) catalysts with different NiO loadings were prepared by impregnation method. The monolayer dispersion capacity of NiO is determined to be about 9 wt.% through XRD quantitative phase analysis. Positron lifetime spectra measured for NiO/Al(2)O(3) catalysts comprise two long and two short lifetime components, where the long lifetimes τ(3) and τ(4) correspond to ortho-positronium (o-Ps) annihilation in microvoids and large pores, respectively. With increasing loading of NiO from 0 to 9 wt.%, τ(4) drops drastically from 88 to 38 ns. However, when the NiO loading is higher than 9 wt.%, τ(4) shows a slower decrease. Variation of λ(4) (1/τ(4)) as a function of the NiO content can be well fitted by two straight lines with different slopes. The relative intensity of τ(4) also shows a fast decrease followed by a slow decrease for the NiO content lower and higher than 9 wt.%, respectively. The coincidence Doppler broadening measurements reveal a continuous increase of S parameter with increasing NiO loading up to 9 wt.% and then a decrease afterwards. This is due to the variation in intensity of the narrow component contributed by the annihilation of para-positronium (p-Ps). Our results show that the annihilation behavior of positronium is very sensitive to the dispersion state of NiO on the surface of γ-Al(2)O(3). When the NiO loading is lower than monolayer dispersion capacity, spin conversion of positronium induced by NiO is the dominant effect, which causes decrease of the longest lifetime and its intensity but increase of the narrow component intensity. After the NiO loading is higher than monolayer dispersion capacity, the spin conversion effect becomes weaker and inhibition of positronium formation by NiO is strengthened, which results in decrease of both the long lifetime intensity and the narrow component intensity. The reaction rate constant is determined to be (1.50 ± 0.04) × 10(10) g mol(-1) s(-1) and (3.43 ± 0.20) × 10(9) g mol(-1) s(-1) for NiO content below and above monolayer dispersion capacity, respectively.     

Ein meta-Xylylen durch Bamford-Stevens-Reaktion eines Fulven-Keten-Addukts

A meta-Xylylene by Bamford-Stevens Reaction of a Fulvene-Ketene-Adduct Heating the sodium salt 8 of the tosylhydrazone 4 of 4-isopropyliden-7,7-dimethylbicyclo[3.2.0]hept-2-en-6-one ( 3 ; obtained by the addition of dimethylketene to 6,6-dimethylfulvene ( 1 )), in diglyme at 130° led to the cotamethyl-[2.2]metacyclophane 10 (17%). The latter probably was formed by dimerization of the non-Kékulé molecule m-xylylene 14 , which, in turn, could have arisen via the homofulvene 13 from the carbene 12 . A second product in the thermolysis of 8 was the tricycle 9 (9 %), as a result of an intramolecular insertion of the carbene C-atom in 12 into a methyl C,H-bond. Further products were the azines 11a , 11b (50%), of the type known as byproducts in Bamford-Stevens reactions. Heating dry 8 afforded 9 (9%) and the two benzene derivatives 15 (9%) and 16 (3%). The tosylhydrazone 4 could be recovered by reaction of 11a , 11b with p-toluenesulfonohydrazide.     

Effective virtual screening protocol for CYP2C9 ligands using a screening site constructed from flurbiprofen and S-warfarin pockets

An effective virtual screening protocol was developed against an extended active site of CYP2C9, which was derived from X-ray structures complexed with flubiprofen and S-warfarin. Virtual screening has been effectively supported by our structure-based pharmacophore model. Importance of hot residues identified by mutation data and structural analysis was first estimated in an enrichment study. Key role of Arg108 and Phe114 in ligand binding was also underlined. Our screening protocol successfully identified 76% of known CYP2C9 ligands in the top 1% of the ranked database resulting 76-fold enrichment relative to random situation. Relevance of the protocol was further confirmed in selectivity studies, when 89% of CYP2C9 ligands were retrieved from a mixture of CYP2C9 and CYP2C8 ligands, while only 22% of CYP2C8 ligands were found applying the structure-based pharmacophore constraints. Moderate discrimination of CYP2C9 ligands from CYP2C18 and CYP2C19 ligands could also be achieved extending the application domain of our virtual screening protocol for the entire CYP2C family. Our findings further demonstrate the existence of an active site comprising of at least two binding pockets and strengthens the need of involvement of protein flexibility in virtual screening.     

Separation of conjugated linoleic acid methyl esters by silver-ion high performance liquid chromatography in semi-preparative mode

Silver-ion HPLC (Ag-HPLC) has been utilized to separate a variety of unsaturated fatty acid methyl esters (FAMEs) by configuration, location or number of olefinic or acetylenic bonds. Two analytical Ag-HPLC columns connected in series and an isocratic solvent system of acetonitrile (ACN) in hexane were used to fractionate 10-15 mg samples of a mixture of two deuterium-labeled isomers of conjugated linoleic acid (Z9.E11- and Z9,Z11-octadecadienoic acid-17,17,18,18-d4). "Baseline" (> 95%) resolution of the two isomers, which decreased with increasing weights of sample injected, was maintained by careful adjustment of the percentage of ACN in the ACN/hexane solvent system. Chemical purities of the isolated FAME were > 96%.     

Phase behavior of blends of PCBM with amorphous polymers with different aromaticity

The phase behavior of [6,6]‐phenyl C₆₁‐butyric acid methyl ester (PCBM) blends with amorphous polymers with different degrees of aromaticity has been investigated by differential scanning calorimetry (DSC) and small‐angle neutron scattering (SANS). The polymers investigated are the homologous series of polystyrene (PS), poly(2‐vinyl‐naphthalene) (P2VN), and poly(9‐vinyl‐phenanthrene) (P9VPh). The DSC results show that the miscibility of PCBM in these polymers increases nonlinearly from 16.5 wt % in PS, 57.0 wt % in P2VN, and 74.9 wt % in P9VPh. The SANS results show that at all concentrations of PCBM, the blends are composed of two mixed phases. Analysis shows that the phase dimensions remain largely independent of PCBM content, but there is a strong dependence of the PCBM concentration difference in the two phases with increasing PCBM content. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 994–1001