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1.
Known determinations of the absolute configuration of guaianolides were collected and found to be few. The absolute configurations of guaianolides rest on the assumption that 7-H always has alpha-orientation. For matricin, only the relative configuration was determined. On the basis of a detailed study of the NMR spectra of matricin and its epimers, and of synthetic, NMR, and CD studies with its decomposition product, chamazulene carboxylic acid, we were able to reconfirm the accepted 3S,3aR,4S,9R,9aS,9bS configuration of matricin. 相似文献
2.
Two ent-rosane- (cuzcol, 1 and 6-dehydroxycuzcol, 2) and a abietatriene- (salvadoriol, 3) type diterpenoids have been isolated from Maytenus cuzcoina and Crossopetalum uragoga, respectively, along with five known diterpene compounds (4-8). Their stereostructures have been elucidated on the basis of spectroscopic analysis, including 1D and 2D NMR techniques, and computational data. The absolute configuration of cuzcol was determined by application of Riguera ester procedure. This is the first instance of isolation of ent-rosane diterpenoids from species of the Celastraceae. The isolated diterpenes were found to be potent anti-tumour-promoter agents, and carnosol (7) also showed a remarkable chemopreventive effect in an in vivo two-stage carcinogenesis model. 相似文献
3.
The absolute configuration of beta-hydroxy-alpha-amino acids was studied by CD exciton chirality method using 7-diethylaminocoumarin-3-carboxylate as a red-shifted chromophore. The CD spectra of bischromophoric derivatives of (S)-serine and (2S,3R)-threonine methyl esters (2 and 7) were compared with those of acyclic vic-aminoalcohols and diols (3--6 and 8--9). This study indicates that the polar carboxylate group of beta-hydroxy-alpha-amino acids makes them a unique subclass of vic-aminoalcohols. By combining the data of CD and NMR coupling constants, we are able to correlate their preferred conformer B and positive CD to the corresponding absolute configuration. 相似文献
4.
Sallam MA 《Chirality》2006,18(10):790-798
The circular dichroism (CD) of a series of acyclic C-nucleoside analogs; 4-(pentahydroxypentyl-1-yl)-2-phenyl-2H-1,2,3-triazoles [1-5] and 4-(D-glycero-D-gulo)-2-phenyl-2H-1,2,3-triazole 6, are reported. A correlation between the sign of the Cotton effect at the maximal UV absorption and the absolute configuration of the carbon atom alpha- to the triazole base moiety is reported. The CD of anomeric 4-(alpha,beta-D-arabinofuranosyl)- and 4-(alpha,beta-D-arabinopyranosyl)-2-phenyl-2H-1,2,3-triazole C-nucleosides are reported. The assignment of the anomeric configuration of C-glycosyl-2-phenyl-2H-1,2,3-triazoles from their CD spectra was found to be a simple method that relies on comparison of the sign of the Cotton effect at the maximal UV absorption and the absolute configuration of the anomeric carbon atom. A correlation between the anomeric configuration and the sign of the Cotton effect at the maximal UV absorption is deduced and generalized as a rule for prediction of the anomeric configuration of C-glycosyl-2-phenyl-2H-1,2,3-triazoles. Nuclear Overhauser effect and 13C NMR spectra supported the CD assignment rule. 相似文献
5.
Kasai Y Taji H Fujita T Yamamoto Y Akagi M Sugio A Kuwahara S Watanabe M Harada N Ichikawa A Schurig V 《Chirality》2004,16(9):569-585
A novel methodology using a chiral molecular tool of MalphaNP acid (1), 2-methoxy-2-(1-naphthyl)propionic acid, useful for preparation of enantiopure secondary alcohols and determination of their absolute configurations by the (1)H NMR anisotropy method was developed; racemic MalphaNP acid (1) was enantioresolved with (-)-menthol, and the enantiopure MalphaNP acid (S)-(+)-(1) obtained was allowed to react with racemic alcohol, yielding a mixture of diastereomeric esters, which was clearly separated by HPLC on silica gel. By applying the sector rule of (1)H NMR anisotropy effect, the absolute configuration of the first-eluted MalphaNP ester was unambiguously determined. Solvolysis or reduction of the first-eluted MalphaNP esters yielded enantiopure alcohols. 相似文献
6.
Three new sesquiterpene acids, xylaric acids A-C (1-3, resp.), and a new tetralone (=3,4-dihydronaphthalen-1(2H)-one) derivative, 4, along with nine known compounds, xylaric acid D (5), hydroheptelidic acid (6), gliocladic acid (7), chlorine heptelidic acid (8), trichoderonic acid A (9), 16-(α-D-mannopyranosyloxy)isopimar-7-en-19-oic acid (10), 16-(α-D-glucopyranosyloxy)isopimar-7-en-19-oic acid (11), 5-carboxymellein (12), and naphthalen-1,8-diol 1-O-α-D-glucopyranoside (13) have been isolated from the solid culture of the ascomycete fungus Xylaria sp. associated with termite nest. The structures of these compounds were elucidated primarily by NMR experiments. The absolute configurations of compounds 1-3 and 5-9 were determined by combination of X-ray data and CD spectral analysis. The absolute configuration of 4 was assigned by Snatzke's method. Compounds 8 and 11 showed slight cytotoxicities against two cell lines A549 and SGC7901. 相似文献
7.
Elsässer B Krohn K Akhtar MN Flörke U Kouam SF Kuigoua MG Ngadjui BT Abegaz BM Antus S Kurtán T 《化学与生物多样性》2005,2(6):799-808
The absolute configurations of plumericin (1) and isoplumericin (2), isolated from Plumeria rubra, were re-assigned based on a combination of X-ray crystal-structure determination and quantum-mechanical calculations of their circular dichroism (CD) spectra. The experimental CD spectra showed an excellent match with those calculated for the (1S,5R,8R,9R,10R) absolute configuration (corresponding to ent-1 and ent-2, resp.), opposite to that generally accepted and published in the literature. Since the (false) plumericin configuration has been often used to derive the absolute configuration of related iridoids by chemical correlation, their absolute configurations also have to be reconsidered. 相似文献
8.
Jang DS Su BN Pawlus AD Kang YH Kardono LB Riswan S Afriastini JJ Fong HH Pezzuto JM Kinghorn AD 《Phytochemistry》2006,67(16):1832-1837
A C29-triterpene, beccaridiol (1), a dihydrochalcone natural product, 2',4'-dihydroxy-3-(4-methoxyphenyl)-propiophenone (2), as well as three known compounds, 4'-hydroxy-1',2'-dihydro-beta-ionone, 4'-O-methyldavidigenin (3), and ursolic acid, have been isolated from an EtOAc-soluble extract of the leaves of Diplectria beccariana. Beccaridiol (1) was characterized as an ursane-type 28-nortriterpene possessing an unusual aromatic E-ring by spectroscopic data interpretation. The relative configuration of this unusual isolate was established by analyzing the observed NOESY NMR correlations, and the absolute stereochemistry of 1 was then determined based on the circular dichroism (CD) spectrum of its 2,3-di-p-bromobenzoate (1b) derivative. All isolates were evaluated for their potential cancer chemopreventive properties utilizing a cell culture assay to determine quinone reductase induction. 相似文献
9.
假地枫皮中二萜酸类化合物研究 总被引:5,自引:0,他引:5
黄平 《天然产物研究与开发》2005,17(3):309-312
从八角属植物假地枫皮的石油醚提取物中分离出5个二萜酸类化合物,经波谱数据分析(^1H NMR、^13C NMR、^1H-^1H COSY、NOESY、HSQC和HMBC),分别鉴定为4-epi-dehydroabietic acid(1)、4-epi-sandaraeopinaric acid(2)、4-epi-abietic acid(3)、4-epi-isopimaric acid(4)和8,11,13,15-abietatetraen-19-oic acid(4)。 相似文献
10.
11.
Valeria Costantino Ernesto Fattorusso Alfonso Mangoni Cristina Perinu Giuseppe Cirino Luana De Gruttola Fiorentina Roviezzo 《Bioorganic & medicinal chemistry》2009,17(21):7542-7547
Tedanol, a new brominated and sulfated pimarane diterpene was isolated from the Caribbean sponge Tedania ignis. Structure of tedanol was elucidated by mass spectroscopy and extensive NMR studies (including spectral simulation), and its absolute configuration was determined using the Mosher method. Tedanol showed a potent anti-inflammatory activity at 1 mg/kg evaluated in vivo in a mouse model of inflammation. After a single intraperitoneal administration, tedanol significantly reduced both the acute and the subchronic phases of carrageenan-induced inflammation. The anti-inflammatory activity was coupled with a strong inhibition of COX-2 expression, inhibition of cellular infiltration measured as mieloperoxidase (MPO) levels, and inhibition of iNOS expression. These features make tedanol a promising template for the development of new anti-inflammatory molecules with low gastrointestinal toxicity. 相似文献
12.
A convenient method for determining the absolute configuration of chiral secondary alcohols using the racemic NMR anisotropy reagent, (+/-)-2-methoxy-2-(1-naphthyl)propionic acid [(+/-)-M(alpha)NP acid], and an HPLC-CD detector was developed. The method was successfully applied to some chiral alcohols derived from (-)-alpha-santonin. 相似文献
13.
Harada N 《Chirality》2008,20(5):691-723
To determine the absolute configurations of chiral compounds, many spectroscopic and diffraction methods have been developed. Among them, X-ray crystallographic Bijvoet method, CD exciton chirality method, and the combination of vibrational circular dichroism and quantum mechanical calculations are of nonempirical nature. On the other hand, X-ray crystallography using a chiral internal reference, and 1H NMR spectroscopy using chiral anisotropy reagents are relative and/or empirical methods. In addition to absolute configurational determinations, preparations of enantiopure compounds are strongly desired. As chiral reagents useful for both the preparation of enantiopure compounds by HPLC separation and the simultaneous determination of their absolute configurations, we have developed camphorsultam dichlorophthalic acid (CSDP acid) for X-ray crystallography and 2-methoxy-2-(1-naphthyl)propionic acid (MalphaNP acid) for 1H NMR spectroscopy. In this review, the principles and applications of these X-ray and NMR methods are explained using mostly our own data. 相似文献
14.
Dibenzocyclooctadiene-type lignans from Magnolia pyramidata 总被引:2,自引:0,他引:2
Eight dibenzocyclooctadiene-type lignans, pyramidatin A-H, were isolated from the leaves of Magnolia pyramidata. Their structures were established by spectral methods, mainly 2D NMR spectroscopic techniques, which involved combined applications of COSY, DEPT. 1H, 13C correlations, COLOC, INAPT and long-range inverse 1H, 13C NMR correlations. The molecular structures of pyramidatin A and B were determined by single crystal X-ray diffraction. The absolute configurations of all eight lignans were derived from CD spectral correlations with structurally related dibenzocyclooctadienes of known absolute configuration. 相似文献
15.
Krohn K;Zia-Ullah Hussain H Flörke U Schulz B Draeger S Pescitelli G Salvadori P Antus S Kurtán T 《Chirality》2007,19(6):464-470
Three new massarilactones E-G (1-3) and the massarilactone acetonide (4) were isolated from the ethyl acetate extract of the endophytic fungus Coniothyrium sp., associated with the plant Artimisia maritima. Their structures were determined by analysis of the 1D and 2D NMR and mass spectroscopic data. The structure of massarilactones E (1) was confirmed by X-ray diffraction analysis, and its absolute configuration determined by the solid-state CD/TDDFT method. 相似文献
16.
Two new daphne diterpene esters Yuanhuajine (2) and Yuanhuagine (4), together with three known daphne diterpene esters yuanhuacine (1), yuanhuadine (3), and yuanhuapine (5), were isolated and identified from Daphne genkwa, a traditional Chinese medicine. Their structures were elucidated by a combination of UV, IR, MS and NMR ((1)H NMR, (13)C NMR, HSQC, and HMBC) spectra. In order to explore the structure-activity relationship, three compounds 6, 7, and 8 were prepared as three derivatives of 1. Inhibitory activities against DNA topoisomerase I (topo I) were assessed for the compounds 1-8. These compounds, except for 8, exhibited potent inhibitory activities against DNA topo I at IC(50) levels of 11.1-53.4 microM and they are new type of topo I inhibitors bearing different structures compared with the known topo I inhibitors. The agarose-gel electrophoresis experiments showed that the orthoester group of daphne diterpene esters was necessary for the inhibitory activity against DNA topo I, and the inhibition against DNA topo I is probably one of the anti-tumor mechanisms of daphne diterpene esters. 相似文献
17.
Azzolina O Collina S Urbano M Fata E Loddo G Linati L Lanza E Barbieri A 《Chirality》2006,18(10):841-848
The diastereoselective synthesis via Grignard reaction of enantiopure analgesic naphthylaminoalcohols has been performed. The chiral racemic key intermediate 3-dimethylamino-2-methyl-1-(naphthalen-2-yl)propan-1-one and enantiomers were prepared and transformed into the desired compounds by addition of the organometallic reagent. The chemical characterization of all diastereoisomers was accomplished by 1H NMR and HPLC analyses and the absolute configuration assigned by CD spectroscopy. The in vitro and in vivo profile has also been evaluated. 相似文献
18.
Identification and isolation of (R(S)R(C))-S-(methylthiomethyl)cysteine-4-oxide from rhizomes of Tulbaghia violacea Harv. is reported. The structure and absolute configuration of the amino acid have been determined by NMR, MALDI-HRMS, IR, and CD spectroscopy. Its content varied in different parts of the plant (rhizomes, leaves, and stems) between 0.12 and 0.24 mg g(-1) fr. wt, being almost equal in the stems and rhizomes. In addition, S-methyl- and S-ethylcysteine derivatives have been detected in minute amounts (<3 microg g(-1) fr. wt) in all parts of the plant. The enzymatic cleavage of the amino acid and subsequent odor formation are discussed. 2,4,5,7-Tetrathiaoctane-4-oxide, the primary breakdown product, has been detected and isolated for the first time. 相似文献
19.
The absolute configuration of the chiral thyroid hormone analog KAT-2003 (+)-2, showing hypocholesterolemic activities, decreases of hepatic triglyceride contents with lowering cardiac side effects, and significant inhibitory effect for the second primary hepatocellular carcinoma, was determined as S by the (1)H NMR anisotropy method using a novel chiral auxiliary, 2-methoxy-2-(1-naphtyl)propionic acid (MalphaNP acid). 相似文献
20.
Chaetoglobosin Vb from endophytic Chaetomium globosum: absolute configuration of chaetoglobosins 总被引:1,自引:0,他引:1
One new cytochalasan alkaloid, chaetoglobosin V(b) (1), together with two structurally related known compounds, chaetoglobosin V (2) and chaetoglobosin G (3), was isolated from the ethyl acetate extract of a culture of the endophytic fungus Chaetomium globosum, associated with the leaves of Ginkgo biloba tree. The structures of the isolated compounds were elucidated by spectroscopic methods including 1D and 2D NMR and mass spectrometry. The absolute configuration of chaetoglobosin V(b) (1) was established by means of electronic circular dichroism (CD) spectroscopy, on the basis of the comparison between the CD spectrum of (+)-1 with that calculated with time-dependent density functional theory method for a simplified model. The correlation between compounds 1-3 was demonstrated by a biomimetic transformation of chaetoglobosin G (3) under mild conditions in chaetoglobosins V and V(b) (1 and 2). The isolated metabolites were tested against some phytopathogens. 相似文献