bluuebunny/crossref_metadata_2025_split huggingface dataset:
Copolymers Comprising 2,7‐Carbazole and Bis‐benzothiadiazole Units for Bulk‐Heterojunction Solar Cells
Authors: Kim Jonggi , Yun Myoung Hee , Anant Piyush , Cho Shinuk , Jacob Josemon , Kim Jin Young , Yang Changduk 
Published: November 2011

AbstractOn the basis of theoretical considerations of the intramolecular charge transfer (ICT) effect, we have designed a series of donor (D)–acceptor (A) conjugated polymers based on bis‐benzothiadiazole (BBT). A PPP‐type copolymer of electron‐rich 2,7‐carbazole (CZ) and electron‐deficient BBT units poly[N‐(2‐decyltetradecyl)‐2,7‐carbazole‐co‐7,7′‐{4,4′‐bis‐(2,1,3‐benzothiadiazole)}] (PCZ‐BBT), a PPV‐type copolymer poly[N‐(2‐decyltetradecyl)‐2,7‐carbazolevinylene‐co‐7,7′‐{4,4′‐bis‐(2,1,3‐benzothiadiazolevinylene)}] (PCZV‐BBTV), and a tercopolymer based on carbazole, thiophene, and BBT poly[N‐(2‐decyltetradecyl)‐2,7‐(di‐2‐thienyl)carbazole‐co‐7,7′‐{4,4′‐bis‐(2,1,3‐benzothiadiazole)}] (PDTCZ‐BBT) have been synthesized to understand the influence of BBT acceptor structure and linkage on the photovoltaic characteristics of the resulting materials. Both the HOMO and LUMO of the resulting polymers are found to be deeper‐lying than those of benzothiadiazole‐based polymers. The measured electrochemical band gaps (eV) are in the following order: PDTCZ‐BBT (1.65 eV) < PCZV‐BBTV (1.69 eV) < PCZ‐BBT (1.75 eV). All the polymers provide a photovoltaic response when blended with a fullerene derivative as an electron acceptor. The best cell reaches a power conversion efficiency of 2.07 % estimated under standard solar light conditions (AM1.5G, 100 mW cm−2). We demonstrate for the first time that BBT‐based polymers are promising materials for use in bulk‐heterojunction solar cells.
Squaraine Dyes as Efficient Coupling Bridges between Triarylamine Redox Centres
Authors: Völker Sebastian F. , Renz Manuel , Kaupp Martin , Lambert Christoph 
Published: November 2011

AbstractVarious indolenine squarylium dyes with additional electron‐donating amine redox centres have been synthesised and their redox chemistry has been studied. A combination of cyclic voltammetry, spectro‐electrochemistry and DFT calculations has been used to characterise the electronic structure of the mono‐, di‐ and, in one case, trications. All monocations still retain the cyanine‐like, delocalised character due to the relatively low redox potential of the squaraine bridge and are therefore compounds of Robin–Day class III. Thus we extended previous studies on organic mixed‐valence systems by using the indolenine squaraine moiety as very electron‐rich bridge between two electron‐donating amine redox centres to provoke a strong coupling between the additional redox centres. We synthesised TA3, which has an N–N distance of 26 bonds between the triarylamine redox centres and is to our knowledge the longest bis(triarylamine) radical cation that is completely delocalised. We furthermore show that altering the symmetry of a squaraine dye by substitution of a squaric ring oxygen atom by a dicyanomethylene group has a direct impact on the optical properties of the monocations. In case of the dications, it turned out that the energetically most stable state of dianisylamine‐substituted squaraines is an anti‐ferromagnetically coupled open‐shell singlet state.
The Ventriculophasic Response Revisited: Analysis of Clinical Correlations Using a New Proposed Definition Derived in Pacemaker Patients
Authors: Dadu Razvan T. , McPherson Craig A. 
Published: November 2011

AbstractBackground:The ventriculophasic response (VR) refers to shortening of atrial cycle length during heart block when a QRS complex is interposed between P waves. No formal quantitative definition has heretofore been proposed, nor have its potential clinical correlations been studied.Hypothesis:We hypothesized that VR is present in selected patients who are distinguished by clinical features from those who lack VR.Methods:Pacing devices were temporarily programmed to VVI mode at 30 ppm as electrocardiogram and intracardiac electrograms were recorded at 50 mm/sec paper speed. We measured the percentage decrease in a P‐P interval (A‐A interval on the atrial electrogram) containing a QRS, compared to the preceding P‐P interval. Left ventricular ejection fraction (LVEF) was measured by echocardiogram.Results:Shortening of P‐P interval was observed chiefly when the interposed QRS occurred early in the anticipated P‐P interval (as judged by the preceding P‐P interval). P‐P shortening of 0% to 3% occurred randomly. Defining VR as being a >3% P‐P interval shortening when an interposed QRS occurred in the first 60% of the anticipated P‐P interval, we found that VR was present in 28 (55%) of our patients. It was quite reproducible, was more common in women (81% vs 37% of men; P = 0.004), and positively correlated with LVEF (r = 0.41, P = 0.004). It did not correlate with age, diabetes, or β‐blocker use.Conclusions:Using our newly derived definition of VR, we found the phenomenon was present in 55% of our patients. It was reproducible and more commonly seen in women and patients with LVEF ≥40%. © 2011 Wiley Periodicals, Inc.The authors have no funding, financial relationships, or conflicts of interest to disclose.
Comparison of Aortic and Carotid Arterial Stiffness Parameters in Patients With Verified Coronary Artery Disease
Authors: Gaszner Balázs , Lenkey Zsófia , Illyés Miklós , Sárszegi Zsolt , Horváth Iván G. , Magyari Balázs , Molnár Ferenc , Kónyi Attila , Cziráki Attila 
Published: November 2011

AbstractBackground:Arterial stiffness parameters are commonly used to determine the development of atherosclerotic disease. The independent predictive value of aortic stiffness has been demonstrated for coronary events.Hypothesis:The aim of our study was to compare regional and local arterial functional parameters measured by 2 different noninvasive methods in patients with verified coronary artery disease (CAD). We also compared and contrasted these stiffness parameters to the coronary SYNTAX score in patients who had undergone coronary angiography.Methods:In this study, 125 CAD patients were involved, and similar noninvasive measurements were performed on 125 healthy subjects. The regional velocity of the aortic pulse wave (PWVao) was measured by a novel oscillometric device, and the common carotid artery was studied by a Doppler echo‐tracking system to determine the local carotid pulse wave velocity (PWVcar). The augmentation index (AIx), which varies proportionately with the resistance of the small arteries, was recorded simultaneously.Results:In the CAD group, the PWVao and aortic augmentation index (Alxao) values increased significantly (10.1 ± 2.3 m/sec and 34.2% ± 14.6%) compared to the control group (9.6 ± 1.5 m/sec and 30.9% ± 12%; P < 0.05). We observed similar significant increases in the local stiffness parameters (PWVcar and carotid augmentation index [Alxcar]) in patients with verified CAD. Further, we found a strong correlation for PWV and AIx values that were measured with the Arteriograph and those obtained using the echo‐tracking method (r = 0.57, P < 0.001 for PWV; and r = 0.65, P < 0.001 for AIx values).Conclusions:Our results indicate that local and regional arterial stiffness parameters provide similar information on impaired arterial stiffening in patients with verified CAD. © 2011 Wiley Periodicals, Inc.This study was supported by the Hungarian National Research Foundation (OTKA) No.78480. The authors have no other funding, financial relationships, or conflicts of interest to disclose.
Vectorial color
Authors: Worthey James A. 
Published: November 2011

AbstractA set of orthonormal color matching functions is developed, in which the first is an all‐positive achromatic function, the second is red–green, and the third can be loosely described as blue–yellow. The achromatic function, proportional to the familiar
$ \bar y $, is a sum of red and green cones. The red–green function uses the same cone sensitivities, but subtracted, with coefficients so that it is orthogonal to the achromatic one. The third function involves all three cones, but is primarily a blue sensitivity. Using this basis to compute the tristimulus vectors of narrow‐band lights at unit power gives Jozef Cohen's locus of unit monochromats, (LUM) an invariant shape now graphed in a space where the axes have intuitive meaning. The extreme points of the LUM reveal the wavelengths that act most strongly in mixtures, a close approximation to William Thornton's Prime Colors. In effect, decades of research converge in three functions and a vectorial schema, demystifying such issues as color rendering and the selection of additive primaries. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2011.
Probing the Effects of One‐Electron Reduction and Protonation on the Electronic Properties of the Fe‐S Clusters in the Active‐Ready Form of [FeFe]‐Hydrogenases. A QM/MM Investigation.
Authors: Greco Claudio , Bruschi Maurizio , Fantucci Piercarlo , Ryde Ulf , De Gioia Luca 
Published: November 2011

AbstractA QM/MM investigation of the active‐ready (Hox) form of [FeFe]‐hydrogenase from D. desulfuricans, in which the electronic properties of all Fe‐S clusters (H, F and F′) have been simultaneously described using DFT, was carried out with the aim of disclosing a possible interplay between the H‐cluster and the accessory iron‐sulfur clusters in the initial steps of the catalytic process leading to H2 formation. It turned out that one‐electron addition to the active‐ready form leads to reduction of the F′‐cluster and not of the H‐cluster. Protonation of the H‐cluster in Hox is unlikely, and in any case it would not trigger electron transfer from the accessory Fe4S4 clusters to the active site. Instead, one‐electron reduction and protonation of the active‐ready form trigger electron transfer within the protein, a key event in the catalytic cycle. In particular, protonation of the H‐cluster after one‐electron reduction of the enzyme lowers the energy of the lowest unoccupied molecular orbitals localized on the H‐cluster to such an extent that a long‐range electron transfer from the F′‐cluster towards the H‐cluster itself is allowed.
Transparency of GaN substrates in the mid‐infrared spectral range
Authors: Welna M. , Kudrawiec R. , Motyka M. , Kucharski R. , Zając M. , Rudziński M. , Misiewicz J. , Doradziński R. , Dwiliński R. 
Published: November 2011

AbstractTransparency of truly bulk GaN substrates obtained by ammonothermal method was measured in the mid infrared spectral range by Fourier spectroscopy. The same measurements were performed for GaN templates grown by meatlorganic vapour phase epitaxy on sapphire and SiC substrates. It has been clearly observed that truly bulk GaN substrates are transparent up to ∼7 µm whereas GaN templates grown on sapphire and SiC are transparent only up to ∼6.5 and ∼5.5 µm, respectively, due to non‐transparency of sapphire and SiC in this spectral range. It has been shown that the transparency “cut off” at ∼7 µm for GaN crystals results from the absorption of light by the second harmonic of optical phonons, which is very significant due to the strong electron‐phonon coupling in this material. Also it has been clearly presented that the absorption “cut‐off” in the infrared spectral region can be easily tuned by increasing of free carrier concentration in GaN. It was observed that the infrared transparency can be shifted from ∼7 to ∼2 µm or even shorter wavelengths when the electron concentration is increased up to ∼1019 cm‐3. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Substituent and solvent effects on UV‐visible absorption spectra of liquid crystalline disubstituted biphenylcyclohexane derivatives – a computational approach
Authors: Lakshmi Praveen P. , Ojha D. P. 
Published: November 2011

AbstractA computational approach has been carried out on liquid crystalline disubstituted biphenylcyclohexanes (BCHs) of general formula R‐C6H10‐C6H4‐C6H4‐X with R: C3H7; X: H (BCH30) and R: C5H11; X: CN (BCH5CN) using the CNDO/S + CI and INDO/S + CI methods. These methods have been employed to calculate and analyze the spectral shifts, and absorbance measurements in UV‐visible range of the systems. The electronic transitions, absorption wavelength, HOMO (Highest Occupied Molecular Orbital), and LUMO (Lowest Unoccupied Molecular Orbital) energies have been calculated. Further, ultraviolet (UV) stability of the molecules has been discussed in the light of absorption wavelength and electronic transition oscillator strength (f). The effect of different solvent media and substituents on transition energies, oscillator strength, and other absorption parameters has also been reported. The present article provides valuable information regarding enhancing the UV stability of molecules by marinating their conductivity. Further, these absorption spectra will provide valuable data base for future computational studies, and the other experimental investigations. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
When once is not enough: accounting for CO2 recycling in EOR operations
Authors: Marston Philip M. 
Published: November 2011

AbstractFunding for carbon capture and storage (CCS) demonstration projects is currently under lots of pressure. Phillip Marston puts forward the case that CO2‐based enhanced oil recovery (EOR) offers a potential solution. To really make this work for captured anthropogenic CO2, we need to come up with an accepted accounting protocol for dealing with recycling of CO2 during EOR.
The presumed atypical chemokine receptor CXCR7 signals through Gi/o proteins in primary rodent astrocytes and human glioma cells
Authors: Ödemis Veysel , Lipfert Jana , Kraft Robert , Hajek Peter , Abraham Getu , Hattermann Kirsten , Mentlein Rolf , Engele Jürgen 
Published: November 2011

AbstractSDF‐1/CXCL12 binds to the chemokine receptors, CXCR4 and CXCR7, and controls cell proliferation and migration during development, tumorigenesis, and inflammatory processes. It is currently assumed that CXCR7 would represent an atypical or scavenger chemokine receptor which modulates the function of CXCR4. Contrasting this view, we demonstrated recently that CXCR7 actively mediates SDF‐1 signaling in primary astrocytes. Here, we provide evidence that CXCR7 affects astrocytic cell signaling and function through pertussis toxin‐sensitive Gi/o proteins. SDF‐1‐dependent activation of Gi/o proteins and subsequent increases in intracellular Ca2+ concentration persisted in primary rodent astrocytes with depleted expression of CXCR4, but were abolished in astrocytes with depleted expression of CXCR7. Moreover, CXCR7‐mediated effects of SDF‐1 on Erk and Akt signaling as well as on astrocytic proliferation and migration were all sensitive to pertussis toxin. Likewise, pertussis toxin abolished SDF‐1‐induced activation of Erk and Akt in CXCR7‐only expressing human glioma cell lines. Finally, consistent with a ligand‐biased function of CXCR7 in astrocytes, the alternate CXCR7 ligand, I‐TAC/CXCL11, activated Erk and Akt through β‐arrestin. The demonstration that SDF‐1‐bound CXCR7 activates Gi/o proteins in astrocytes could help to explain some discrepancies previously observed for the function of CXCR4 and CXCR7 in other cell types. © 2011 Wiley Periodicals, Inc.
Exploiting salivary miR‐31 as a clinical biomarker of oral squamous cell carcinoma
Authors: Liu Chung‐Ji , Lin Shu‐Chun , Yang Cheng‐Chieh , Cheng Hui‐Wen , Chang Kuo‐Wei 
Published: November 2011

AbstractBackgroundOral carcinoma is an important malignancy throughout the world. MicroRNAs (miRNAs) are endogenously expressed, non‐coding RNAs that regulate post‐transcriptional levels of targeted mRNAs. MiRNA‐31(miR‐31) is significantly upregulated in oral carcinoma tissues and plays oncogenic roles in oral carcinogenesis.MethodsWe analyzed the levels of miR‐31 in saliva of patients with oral carcinoma (n = 45), oral verrucous leukoplakia (n = 10), and control healthy individuals (n = 24) by quantitative reverse transcriptase‐polymerase chain reaction (RT‐PCR).ResultsSalivary miR‐31 was significantly increased in patients with oral carcinoma at all clinical stages, including very small tumors. However, our preliminary analysis showed no increase of salivary miR‐31in patients with oral verrucous leukoplakia relative to controls. The miR‐31 was more abundant in saliva than in plasma, suggesting salivary miR‐31 was a more sensitive marker for oral malignancy. After excision of oral carcinoma, salivary miR‐31 was remarkably reduced, indicating that most of the upregulated salivary miR‐31 came from tumor tissues.ConclusionOur results point to a potential application of salivary miR‐31 as a biomarker for early detection and postoperative follow‐up of oral carcinoma. © 2011 Wiley Periodicals, Inc. Head Neck, 2012
Radical Cyclization of Fluorinated 1,3‐Dicarbonyl Compounds with Dienes Using Manganese(III) Acetate and Synthesis of Fluoroacylated 4,5‐Dihydrofurans
Authors: Yılmaz Mehmet , Yılmaz E. Vildan Burgaz , Pekel A. Tarık 
Published: November 2011

AbstractRadical cyclizations of fluorinated 1,3‐dicarbonyl compounds with dienes mediated by Mn(OAc)3 afforded 4,5‐dihydrofurans containing difluoroacetyl, trifluoroacetyl, or heptafluorobutanoyl groups in good‐to‐excellent yields. Additionally, 2‐(difluoromethyl)‐4,5‐dihydrofurans and a 4,7‐dihydrooxepin derivative were obtained as unexpected products in the reaction of 4,4‐difluoro‐1‐phenylbutane‐1,3‐dione with 1,3‐diphenylbuta‐1,3‐diene. The radical cyclization of symmetrical dienes such as 2,3‐dimethylbuta‐1,3‐diene and 1,4‐diphenylbuta‐1,3‐diene with 1,3‐diketones furnished the corresponding products in low yields. However, treatment of 1‐phenylbuta‐1,3‐diene with 1,3‐dicarbonyl compounds afforded 4,5‐dihydrofurans containing fluoroacyl groups. The radical cyclizations with 3‐methyl‐1‐phenylbuta‐1,3‐diene and 1,3‐diphenylbuta‐1,3‐diene led to 4,5‐dihydrofurans in good yields, since Me and Ph groups at C(3) of these dienes increase the stability of the radical intermediate.
Euphane Triterpenes from the Bark of Broussonetia papyrifera
Authors: Zhong Han‐Ting , Li Fu , Chen Bin , Wang Ming‐Kui 
Published: November 2011

AbstractFour new euphane triterpenes, (3β)‐3‐(acetyloxy)eupha‐7,25‐dien‐24‐one (1), (3β,24R)‐3‐(acetyloxy)eupha‐7,25‐dien‐24‐ol (2), (3β,24S)‐eupha‐7,25‐diene‐3,24‐diol (3), and (3β,24R)‐eupha‐7,25‐diene‐3,24‐diol (4) were isolated from the barks of Broussonetia papyrifera, a tree whose roots, barks, and fruits were used as herbal drugs in China. The structures of 1–4 were elucidated on the basis of spectroscopic evidence and chemical methods.
The Synthesis of Epiboxidine and Related Analogues as Potential Pharmacological Agents
Authors: Kulu Irem , Ocal Nuket 
Published: November 2011

AbstractMethyl epiboxidine‐N‐carboxylate (8) was synthesized from 7 under reductive Heck conditions (Scheme 2). The CC coupling of the new epiboxidine analog 9 with aryl and heteroaryl halides gave by hydroarylation C‐aryl, N‐(3‐methylisoxazol‐5‐yl)‐substituted tricyclic imides 10a–10f (Table). The [3+2] cycloaddition of 9 with nitrile oxides yielded the bridged dihydroisoxazole derivatives 11a–11d with potential biological activity (Scheme 4).
Acylated Triterpene Saponins from Atroxima libericaStapf
Authors: Tabopda Turibio Kuiate , Mitaine‐Offer Anne‐Claire , Miyamoto Tomofumi , Tanaka Chiaki , Mirjolet Jean‐François , Duchamp Olivier , Ngadjui Bonaventure Tchaleu , Lacaille‐Dubois Marie‐Aleth 
Published: November 2011

AbstractThe four new acylated triterpene saponins 1–4, isolated as two pairs of isomers and named libericosides A1/A2 and B1/B2, one pair of isomers 5/6, the (Z)‐isomer libericoside C2 (5) being new, one new sucrose ester, atroximoside (7), and eight known compounds were isolated from the roots of Atroxima liberica by repeated MPLC and VLC on normal and reversed‐phase silica gel. Their structures were elucidated on the basis of extensive 1D‐ and 2D‐NMR studies (1H‐ and 13C‐NMR, DEPT, COSY, TOCSY, NOESY, HSQC, and HMBC) and mass spectrometry as 3‐O‐β‐D‐glucopyranosylpresenegenin 28‐{O‐α‐L‐arabinopyranosyl‐(1→3)‐O‐β‐D‐xylopyranosyl‐(1→4)‐O‐α‐L‐rhamnopyranosyl‐(1→2)‐4‐O‐[(E)‐3,4‐dimethoxycinnamoyl]‐β‐D‐fucopyranosyl} ester (1) and its (Z)‐isomer 2, 3‐O‐β‐D‐glucopyranosylpresenegenin 28‐{O‐α‐L‐arabinopyranosyl‐(1→4)‐O‐β‐D‐xylopyranosyl‐(1→4)‐O‐α‐L‐rhamnopyranosyl‐(1→2)‐O‐[O‐β‐D‐xylopyranosyl‐(1→3)‐β‐D‐glucopyranosyl‐(1→3)]‐4‐O‐[(E)‐3,4‐dimethoxycinnamoyl]‐β‐D‐fucopyranosyl} ester (3) and its (Z)‐isomer 4, 3‐O‐β‐D‐glucopyranosylpresenegenin 28‐{O‐β‐D‐xylopyranosyl‐(1→4)‐O‐α‐L‐rhamnopyranosyl‐(1→2)‐O‐[6‐O‐acetyl‐β‐D‐glucopyranosyl‐(1→3)]‐4‐O‐[(Z)‐3,4‐dimethoxycinnamoyl]‐β‐D‐fucopyranosyl} ester (5), and 3‐O‐[(Z)‐feruloyl]‐β‐D‐fructofuranosyl α‐D‐glucopyranoside (7). Compounds 1–6 and the known saponins 8/9 were evaluated against the human colon cancer cells HCT 116 and HT‐29 and showed moderate to weak cytotoxicity.
Two New Prenylated Xanthones from the Pericarp of Garcinia mangostana (Mangosteen)
Authors: Zhou Xiaojun , Huang Riming , Hao Jing , Huang Huijuan , Fu Manqin , Xu Zhifang , Zhou Yongmei , Li Xu‐E , Qiu Samuel X. , Wang Bin 
Published: November 2011

AbstractTwo new prenylated xanthones (=9H‐xanthen‐9‐ones), garcimangosxanthones D (1) and E (2), together with the six known xanthones 3–8, were isolated from the pericarp of Garcinia mangostana. Their structures were determined by analysis of their spectroscopic data. All of the isolated compounds were biologically evaluated for their in vitro cytotoxic activity against A549, Hep‐G2, and MCF‐7 human‐cancer cell lines and antioxidant activity. Compound 1 exhibited moderate cytotoxicity against Hep‐G2 (IC50=19.2 μM) and weak cytotoxicity against MCF‐7 (IC50=62.8 μM) cell lines, and compound 2 showed moderate cytotoxicity against A549, Hep‐G2, and MCF‐7 cell lines with IC50 values of 12.5–20.0 μM (Table 2). Both compounds 1 and 2 demonstrated a weak antioxidant activity with ferric reducing antioxidant power (FRAP) values of 41±7 and 130±4 μmol/g, respectively (Table 3).
Bruceines K and L from the Ripe Fruits of Brucea javanica
Authors: Zhao Ming , Lau Sin Ting , Zhang Xiao Qi , Ye Wen Cai , Leung Po Sing , Che Chun‐Tao , Lin Zhi‐Xiu 
Published: November 2011

AbstractBruceine K (1), a pentacyclic C20‐quassinoid bearing a unique 12,20‐epoxy moiety, and bruceine L (2), along with the ten known compounds (6S,7E)‐6,9,10‐trihydroxy‐ and (6S,7E)‐6,9‐dihydroxymegastigma‐4,7‐dien‐3‐one (3 and 4, resp.), cleomiscosins A–C, luteoline, quercetine, bruceantinol, pinoresinol, and thevetiaflavone, were isolated from the ripe fruits of Brucea javanica. Bruceines K (1) and L (2) were determined to be (1β,2α,11β,12β,14ξ,15β)‐12,20‐epoxy‐1,2,11,13,14,15‐hexahydroxypicras‐3‐en‐16‐one and (1β,2α,11β,12β,15β)‐13,20‐epoxy‐1,2,11,12‐tetrahydroxy‐16‐oxo‐15‐(senecioyloxy)picras‐3‐en‐21‐oic acid methyl ester (senecioic acid=3‐methylbut‐2‐enoic acid), respectively, on the basis of NMR (1H‐ and 13C‐NMR, DEPT, 1H,1H‐COSY, NOESY, HMQC, and HMBC) and ESI‐MS data. Among the known compounds, (6S,7E)‐6,9,10‐trihydroxy‐ and (6S,7E)‐6,9‐dihydroxymegastigma‐4,7‐dien‐3‐one (3 and 4, resp.), cleomiscosin C, luteoline, quercetine, and thevetiaflavone were isolated for the first time from the Brucea plants.
Stereochemical Investigation of Macrocyclic Bisbibenzyls with a Stereogenic Center at One of the Ethylene Bridges
Authors: Xie Chun‐Feng , Zhu Rong‐Xiu , Qu Jian‐Bo , Wang Li‐Ning , Guo Dong‐Xiao , Yu Wen‐Tao , Liu Cheng‐Bu , Lou Hong‐Xiang 
Published: November 2011

Abstract7′‐Hydroxyriccardin C (1) and marchantin E (2), two macrocyclic bisbibenzyls with a stereogenic center at the ethylene bridge from Chinese liverworts, were investigated stereochemically. Compound 1 was found to be optically active and occurred as a pair of dynamically interchangeable atropisomers at room temperature due to the low barrier of rotation around the biaryl bond, while 2 was a racemic mixture, which was successfully resolved by chiral HPLC into two enantiomers. Their absolute configurations were unequivocally assigned by analysis of temperature‐dependent NMR spectra, X‐ray crystallographic diffraction, and comparison of experimental and calculated ECD data.