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NMR Assignments (nmr + assignment)
Selected AbstractsJ -Based Analysis and DFT,NMR Assignments of Natural Complex Molecules: Application to 3,,7-Dihydroxy-5,6-epoxycholestanesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2008Jesús Javier Poza Abstract In order to reproduce the stereochemical dispositions of the epoxy and hydroxy functionalities, four 3,,7-hydroxy-5,6-epoxycholestanes were easily prepared from cholesterol, and their NMR spectroscopic data were experimentally obtained from 1D and 2D NMR experiments. An exhaustive QM- J -based analysis was then performed to replicate the experimental H,H and C,H coupling constants as well as the 13C NMR chemical shifts. The B3LYP GIAO methodology with the 6-311-G(d,p) basis set was chosen and showed that the data obtained from rings A and B were sufficient to calculate the correct stereochemistry of the 5,6-epoxy and 7-hydroxy groups. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Complete multinuclear magnetic resonance characterization of a set of polyfluorinated acids and alcoholsMAGNETIC RESONANCE IN CHEMISTRY, Issue 2 2009Alexander A. Marchione Abstract A complete 1H, 19F, and 13C NMR assignment of a homologous series of polyfluorinated acids and alcohols is reported. These assignments were obtained chiefly through single and multiple-bond 1H,13C and 19F,13C correlation experiments (HSQC, HMBC). 19F NOESY experiments were required for assignment of two compounds with diastereotopic 19F nuclei in the CF2chain of the molecule. Copyright © 2008 John Wiley & Sons, Ltd. [source] Complete 1H and 13C NMR assignment for aryl diisoprenesMAGNETIC RESONANCE IN CHEMISTRY, Issue 9 2003Jorge L. Zambrano Abstract The characterization of four aryl diisoprenes was carried out by 1D- and 2D-NMR methods, which permitted the assignment of the signals of all protons and all carbon atoms. Copyright © 2003 John Wiley & Sons, Ltd. [source] Probing multiple effects on 15N, 13C,, 13C,, and 13C, chemical shifts in peptides using density functional theoryBIOPOLYMERS, Issue 6 2002Xiao-Ping Xu Abstract We have used density functional calculations on model peptides to study conformational effects on 15N, 13C,, 13C,, and 13C, chemical shifts, associated with hydrogen bonding, backbone conformation, and side-chain orientation. The results show a significant dependence on the backbone torsion angles of the nearest three residues. Contributions to 15N chemical shifts from hydrogen bonding (up to 8 ppm), backbone conformation (up to 13 ppm), side-chain orientation and neighborhood residue effects (up to 22 ppm) are significant, and a unified theory will be required to account for their behavior in proteins. In contrast to this, the dependence on sequence and hydrogen bonding is much less for 13C, and 13C, chemical shifts (<0.5 ppm), and moderate for carbonyl carbon shifts (<2 ppm). The effects of side-chain orientation are mainly limited to the residue itself for both nitrogen and carbon, but the ,1 effect is also significant for the nitrogen shift of the following residue and for the 13C, shift of the preceding residue. The calculated results are used, in conjunction with an additive model of chemical shift contributions, to create an algorithm for prediction of 15N and 13C shifts in proteins from their structure; this includes a model to extrapolate results to regions of torsion angle space that have not been explicitly studied by density functional theory (DFT) calculations. Crystal structures of 20 proteins with measured shifts have been used to test the prediction scheme. Root mean square deviations between calculated and experimental shifts 2.71, 1.22, 1.31, and 1.28 ppm for N, C,, C,, and C,, respectively. This prediction algorithm should be helpful in NMR assignment, crystal and solution structure comparison, and structure refinement. © 2002 Wiley Periodicals, Inc. Biopolymers 65: 408,423, 2002 [source] Stable Ion and Electrophilic Substitution (Nitration and Bromination) Study of A-Ring Substituted Phenanthrenes: Novel Carbocations and Substituted Derivatives; NMR, X-ray Analysis, and Comparative DNA BindingEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2007Cédric Brulé Abstract Persistent carbocations were generated from five A-ring mono- and di-substituted phenanthrenes [3-OMe; 4-OMe, 1,3-bis(OMe), 2,4-bis(OMe), and 1,3-bis(Me)]. In all cases protonation occurs in the A-ring, ortho/para relative to methoxy or methyl substituent(s). Complete NMR assignments of the resulting carbocations are reported and their charge delocalization modes are discussed. Mild nitration (with 20,50,% aqueous HNO3 at ,10 °C or at room temp.) and bromination (NBS/MeCN/room temp.) of these substrates resulted in the synthesis of several novel mononitro-/dinitro- as well as monobromo/dibromo derivatives, including those with nitro or bromo substituent in the bay-region. Correspondence between the site of attack in low-temperature protonation study and nitro substitution in ambient mild nitrations are examined. Complete NMR assignments for the new derivatives are reported as well as X-ray structures for 2,4-dimethoxy-1-nitro- and 1,3-dimethyl-4-nitrophenanthrenes. A comparative DNA binding study with MCF cells on three of the synthesized mononitro and one dinitro derivative showed that 1,3-dimethyl-9-nitro- (nitro at the meso position), 3-methoxy-4-nitro- (nitro in bay-region), and 1,3-dimethoxy-4,9-dinitrophenanthrenes (nitro in both meso and bay-regions) formed DNA adducts. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Physical image vs structure relation: part 12 , structure of 2,2,5,5-tetramethyl-dihydro-furan-3-one oxime and its protonated forms through isomerization and NMR spectra,JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 6 2007Ryszard B. Nazarski Abstract The study of an isomeric A/B mixture of the title oxime 1, by photolytic or thermal E,Z -isomerization and NMR measurement including 1H{1H}-NOE difference spectra, led to assignment of the E configuration to its predominating form A. The 1H/13C data were interpreted in terms of steric overcrowding of both forms, especially of the thermolabile photoproduct B. Four classical (empirical) NMR methods of elucidating the oxime geometry were critically tested on these results. Unexpected vapor-phase photoconversion A,B in the window glass-filtered solar UV and spectroscopic findings on their protonated states were discussed, as well. The kinetically controlled formation of the N- protonated species (Z)- 5+ was proved experimentally. In addition, some 1H NMR assignments reported for structurally similar systems were rationalized (3 and 4) or revised (1 and 7,9) with the GIAO-DFT(B3LYP) and/or GIAO-HF calculational results. Copyright © 2007 John Wiley & Sons, Ltd. [source] Structure elucidation and NMR assignments of two unusual monoterpene indole alkaloids from Psychotria stachyoidesMAGNETIC RESONANCE IN CHEMISTRY, Issue 9 2010Antonia Torres Ávila Pimenta Abstract Two unusual monoterpene indole alkaloids, stachyoside (1) and nor-methyl-23-oxo-correantoside (2), have been isolated from the aerial parts of Psychotria stachyoides. The structural elucidation of both compounds was performed by the aid of HRESIMS, FT-IR, and 1D- and 2D-NMR techniques including COSY, HSQC, HMBC, and NOESY. Copyright © 2010 John Wiley & Sons, Ltd. [source] 1H and 13C NMR assignments of all three isomeric o -fluoronaphthaldehydes and three o -fluorophenanthrene aldehydesMAGNETIC RESONANCE IN CHEMISTRY, Issue 1 2010Carl A. Busacca Abstract Three isomeric o -fluoronaphthaldehydes, 9-fluorophenanthrene, and three previously unreported o -fluorophenanthrene aldehydes were analyzed in detail by multiple NMR techniques to provide unambiguous assignment of structures and resonances. The six aldehydes serve as the key starting materials for novel chiral ligands used in highly enantioselective rhodium-catalyzed asymmetric hydrogenation reactions. Copyright © 2009 John Wiley & Sons, Ltd. [source] The development of an NMR chemical shift prediction application with the accuracy necessary to grade proton NMR spectra for identityMAGNETIC RESONANCE IN CHEMISTRY, Issue 12 2009Stephen G. Spanton Abstract We have developed an NMR chemical shift prediction system that enables high throughput automatic grading of NMR spectra. In support of high throughput synthetic efforts for our drug discovery program, a rapid and accurate analysis for identity was needed. The system was designed and implemented to take advantage of the NMR assignments that had been tabulated on internally generated research compounds. The system has been operational for four years and has been used in conjunction with an internally written grading program to successfully analyze several hundred thousand samples based only on their 1D 1H spectrum. A focused test of the system's accuracy on 1006 molecules demonstrated the ability to estimate the proton chemical shift with an average error of +/,0.16 ppm. This level of chemical shift accuracy allows for reliable structure confirmation by automated analysis using only proton NMR. Copyright © 2009 John Wiley & Sons, Ltd. [source] Structure elucidation and NMR assignments of two new pyrrolidinyl quinoline alkaloids from chestnut honeyMAGNETIC RESONANCE IN CHEMISTRY, Issue 5 2009Giangiacomo Beretta Abstract The complete 1H, 13C and 15N NMR spectral assignments of two new alkaloids isolated from chestnut honey and structurally related to kynurenic acid have been made using 1-D and 2-D NMR techniques, including COSY, HMQC and HMBC experiments. The new compounds have been identified as 3-(2,-pyrrolidinyl)-kynurenic acid and its ,-lactam derivative. Copyright © 2009 John Wiley & Sons, Ltd. [source] 1H and 13C NMR assignments for two new steroids from the coral Chromonephthea sp.MAGNETIC RESONANCE IN CHEMISTRY, Issue 4 2009Hua-Wei Geng Abstract Two new steroids isolated from EtOH extracts of the South China Sea soft coral Chromonephthea sp. were identified. One-dimensional (1D) and two-dimensional (2D) NMR experiments including COSY, HSQC, HMBC and NOESY were used for the determination of their structure. Copyright © 2008 John Wiley & Sons, Ltd. [source] 1H and 13C NMR assignments for new heterocyclic TAM leuco dyes, (2Z,2,E)-2,2,-(2-phenyl propane-1,3-diylidene) bis(1,3,3-trimethylindoline) derivatives.MAGNETIC RESONANCE IN CHEMISTRY, Issue 9 2008Part II Abstract The 1H and 13C NMR spectra of the novel heterocyclic Leuco-TAM dyes, (2Z, 2,E)-2,2,-(2-phenyl propane-1,3-diylidene) bis(1,3,3-trimethylindoline) derivatives 1,4 as precursors of triarylmethane (TAM)+ (Malachite Green FB-analog) dyes were completely assigned by 1D and 2D NMR experiments, including DEPT, COSY, HSQC, HMBC, and NOESY. Especially, the diastereotopic gem -dimethyl protons at the C3 and C3, positions of the FB rings were definitively assigned. The (Z,E) isomers adopt the energetically favored three-bladed propeller conformation in solution. Copyright © 2008 John Wiley & Sons, Ltd. [source] 1H and 13C NMR assignments for 6-demethylvermistatin and two penicillide derivatives from the mangrove fungus Guignardia sp. (No. 4382) from the South China SeaMAGNETIC RESONANCE IN CHEMISTRY, Issue 7 2008Xue-kui Xia Abstract One new compound 6-demethylvermistatin (1), together with two known compounds, the penicillide derivatives (2) and (3) were isolated from the mangrove fungus Guignardia sp. No. 4382 obtained from the South China Sea. Their structures were assigned using high-resolution electron ionization mass spectrometry(HREIMS), 1H and 13C NMR spectra, DEPT, and by 2D COSY, HMQC, and HMBC experiments. The absolute configuration of 1 was established by comparison of its CD with that of vermistatin. Copyright © 2008 John Wiley & Sons, Ltd. [source] 1H and 13 C NMR assignments for two lignans from the heartwood of Streblus asperMAGNETIC RESONANCE IN CHEMISTRY, Issue 5 2008Jun Li Abstract In our ongoing investigation of the bioactive constituents from plants, two new lignans, magnolignan A-2- O -,- D -glucopyranoside and strebluslignanol were isolated from heartwood of Streblus asper, along with three known lignans, magnolignan A, magnolol, and magnaldehyde D. 1D and 2D NMR experiments, including COSY, HMQC, and HMBC, and other spectroscopic methods, including UV, IR, and MS were used for the determination of the structures and NMR assignments. Primary bioassays showed that magnolignan A-2- O -,- D -glucopyranoside and strebluslignanol have medium cytotoxic activity against HEp-2 and HepG2 cells, with IC50 of 13.3 µM, 46.4 µM and 10.1 µM, 21.7 µM, respectively. Copyright © 2008 John Wiley & Sons, Ltd. [source] Complete 1H and 13C NMR assignments and Z/E-stereoconfiguration determination of isomers of 1,4-diketone derivativesMAGNETIC RESONANCE IN CHEMISTRY, Issue 1 2008Guohua Xu Abstract Complete 1H and 13C NMR assignments and Z/E-stereoconfiguration determination for a series of new isomers of 1,4-diketone derivatives obtained via self-sorting tandem reaction were accomplished by means of one- and two-dimentional NMR experiments including 1H, 13C, gCOSY, gHSQC, gHMBC, and NOESY. Copyright © 2008 John Wiley & Sons, Ltd. [source] Complete 1H and 13C NMR assignments of three new polyhydroxylated sterols from the South China Sea gorgonian Subergorgia suberosaMAGNETIC RESONANCE IN CHEMISTRY, Issue 12 2007Shu-Hua Qi Abstract Three new polyhydroxylated sterols, 3,,6,,11,20,,24-pentahydroxy- 9,11-seco-5,-24-ethylcholest-7,28-diene-9-one (1), 3-(1,,2,-ethandiol)-24- methylcholest-8(9),22E -diene-3,,5,,6,,7,,11,-pentaol (2), 24-methylcholest-7,22 E -diene-3,,5,,6,,25-tetraol (3) together with five known sterols, were isolated from the EtOH/CH2Cl2 extract of the South China Sea gorgonian Subergorgia suberosa. The complete assignments of the 1H and 13C NMR chemical shifts for these new compounds were achieved by means of 1D and 2D NMR techniques, including HSQC, HMBC, 1H1H COSY, and NOESY spectra. Copyright © 2007 John Wiley & Sons, Ltd. [source] 1H and 13C NMR assignments for two new angular furanocoumarin glycosides from Peucedanum praeruptorumMAGNETIC RESONANCE IN CHEMISTRY, Issue 7 2007Haitao Chang Abstract Two novel angular-type furanocoumarin glycosides, peucedanoside A (1) and peucedanoside B (2), along with a known compound apterin (3), were isolated from the roots of Peucedanum praeruptorum Dunn. Their chemical structures were determined by MS, NMR spectroscopy and chemical analysis. Complete assignments of the 1H and 13C NMR spectroscopic data were achieved by 1D and 2D NMR experiments including DEPT, HSQC, HMBC and ROESY. Copyright © 2007 John Wiley & Sons, Ltd. [source] 1H and 13C NMR assignments for two anthraquinones and two xanthones from the mangrove fungus (ZSUH-36)MAGNETIC RESONANCE IN CHEMISTRY, Issue 5 2007Changlun Shao Abstract We report the unambiguous assignments of the 1H and 13C NMR spectra of one new natural product, namely, 6,8-di-O-methyl versiconol (1) together with one known anthraquinone aversin (2) and two xanthones 5-methoxysterigmatocystin (3) and sterigmatocystin (4). These compounds were all isolated from the mangrove endophytic fungus ZSUH-36 from the South China Sea. 1D and 2D NMR experiments including COSY, HMQC and HMBC were used to elucidate the structures. Variations in the 1H NMR spectrum of 6,8-di-O-methyl versiconol (1) were also observed in the temperature range 25,75 °C. In addition, the plausible biogenetic path from 1 to 2 is discussed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Complete 1H and 13C NMR assignments of the epimeric menthane-1-carboxylic acids,MAGNETIC RESONANCE IN CHEMISTRY, Issue 3 2007Debra K. Dillner Abstract Complete NMR analyses with full assignments for 1H and 13C NMR spectral data for both epimers of menthane-1-carboxylic acid are described. The NMR properties of the recently synthesized axial isomer had not been previously described, and through use of a variety of 1D and 2D techniques, additional information is provided for the equatorial isomer. As well as assignments of chemical shifts, homonuclear coupling constants were determined for the equatorial isomer and most of coupling constants were measured for the axial isomer. Published in 2007 by John Wiley & Sons, Ltd. [source] Complete 1H and 13C NMR assignments of sesquiterpene glucosides from Ixeris sonchifoliaMAGNETIC RESONANCE IN CHEMISTRY, Issue 3 2007ZeyEi Na Abstract Four sesquiterpene glucosides were isolated from Ixeris sonchifolia Hance. The structure of a new compound (1) was assigned as 9,-monohydroxy-2,12-dioxo-guaia-3,11(13)-dien-1,,5,,6,,7,,9,,10,H-12,6-olide-9- O -,- D - glucopyranoside (ixerinoside). In addition, unambiguous and complete assignments of 1H NMR chemical shifts for crepidiaside A (2), ixerin Z (3), and 11,13,-dihydroixerin Z (4) are presented. The assignments were achieved by two-dimensional NMR (gCOSY, gHSQC, gHMBC, NOESY) and one-dimensional nuclear Overhauser effect (NOE) experiments. Copyright © 2007 John Wiley & Sons, Ltd. [source] NMR assignments of a di-pentacyclo-undecane cyclic etherMAGNETIC RESONANCE IN CHEMISTRY, Issue 11 2006Hendrik G. Kruger Abstract The X-ray structure of a di-pentacyclo-undecane cyclic ether was recently reported. As part of a programme to use NMR spectroscopy for the structure elucidation of cage compounds, the complete NMR assignments of the cyclic ether was attempted. Major overlap of proton and carbon signals of the two cages is observed. It was required to elucidate the fragment analogues that represent similar structural features of the cyclic ether in order to get an approximate but reasonable insight into the complex overlapping signals. Normal 2D NMR techniques were utilized to assign the various NMR signals. Copyright © 2006 John Wiley & Sons, Ltd. [source] 1H and 13C NMR assignments and X-ray structures for three monocyclic benzoannelated dilactam polyethersMAGNETIC RESONANCE IN CHEMISTRY, Issue 9 2006Gary L. N. Smith Abstract Three monocyclic polyether dilactams, 17,18-dihydro-5H, 9H -dibenzo[e,n]1,4,10,7,13trioxadiazacyclopentadecine-6,10(7H,11H)-dione (1); 9,10,20,21-tetrahydro-5H, 12H -dibenzo[e,q]1,4,10,13,7,16tetraoxadiazacyclooctadecine-6, 13(7H,14H)-dione (2); and 6,7,9,10-tetrahydro-16H, 20H -dibenzo[h,q]1,4,7,13, 10,16tetraoxadiazacyclooctadecine-17, 21(18H,22H)-dione (3) were isolated during the synthesis of several benzoannelated cryptands. The complete assignments of the 1H and 13C NMR spectra of 1, 2 and 3 in CDCl3 were made using gCOSY, gHMBC, gHMQC, HMQC, HSQC, and NOESY 1D techniques. The ortho (H2) benzene protons show significant downfield shifts (1.16,1.43 ppm) that are consistent with an exodentate orientation for the amide carbonyl groups. The X-ray crystal structures of 1, 2 and 3 show that the carbonyl groups adopt an exodentate conformation in the solid state. Copyright © 2006 John Wiley & Sons, Ltd. [source] Two isomeric epoxysitosterols from Rhododendron formosanum: 1H and 13C NMR chemical shift assignmentsMAGNETIC RESONANCE IN CHEMISTRY, Issue 8 2006Vivek Krishna Abstract 1H and 13C NMR assignments of the two isomeric epoxysitosterols, 5,6,-epoxy-5,-stigmastan-3,-ol (1) and 5,6,-epoxy-5,-stigmastan-3,-ol (2), isolated from the leaves of Rhododendron formosanum Hemsl were achieved by 1D and 2D techniques such as DEPT, HMBC, HMQC, COSY and NOESY. Copyright © 2006 John Wiley & Sons, Ltd. [source] Comparison of 17,-estradiol structures from x-ray diffraction and solution NMRMAGNETIC RESONANCE IN CHEMISTRY, Issue 6 2005Fernando Commodari Abstract The NMR-derived structure of estrogen (17,-estradiol, E2), the drug of choice for postmenopausal women, was compared with a recent literature crystal x-ray structure of Fab-bound E2. 1H and 13C NMR spectra of E2 were acquired in DMSO- d6. Assignments were obtained from an analysis of DQF-COSY, TOCSY, HETCOR, HMQC and HMBC 2D NMR spectra. The 1H and 13C NMR assignments are the first reported for E2 in DMSO- d6. Two solution structures, S1 and S2, were obtained with molecular modeling using NOE constraints. S1 overlaps with the crystal structure for all rings. S2 shows prominent differences in the C-ring (C9C11C12C13) segment, which deviates from a chair conformation, and excellent overlap in the A-, B- and D-rings of E2. The C-ring in S2 adopts a boat conformation as opposed to a chair conformation in the x-ray and S1 structures. The S2 structure is about 6° more twisted than the bound x-ray and S1 models. The S1, S2 and x-ray structures had ring bowing values of 10.1 ± 0.3, 11 ± 1 and 10.37°, respectively. Of the 100 solution conformers generated, 83 had S1 conformation and 17 had S2 conformation, with average internal energies of 112 ± 2 and 141 ± 2 kcal mol,1, respectively. The 100 S1 - and S2 - derived conformers showed a r.m.s.d. of 0.72 Ĺ for all atoms. The x-ray, S1 and S2 C18O17 distances were 2.93, 2.92 ± 0.01 and 2.93 ± 0.01 Ĺ, respectively, and the O3O17 distances were 11.06, 11.18 ± 0.12, and 10.89 ± 0.05 Ĺ, respectively. Copyright © 2005 John Wiley & Sons, Ltd. [source] Complete 1H and 13C NMR assignments of four new steroidal glycosides from a gorgonian coral Junceella junceaMAGNETIC RESONANCE IN CHEMISTRY, Issue 3 2005Shuhua Qi Abstract Four new cholest-type steroidal glycosides, junceellosides A,D, isolated from the EtOH/CH2Cl2 extracts of the South China Sea gorgonian coral Junceella juncea, were identified. Complete assignments of the 1H and 13C NMR chemical shifts for these compounds were achieved by means of one- and two-dimensional NMR techniques, including 1H,1H COSY, HSQC, HMBC and NOESY spectra. Copyright © 2004 John Wiley & Sons, Ltd. [source] Characterization of reduced iso-,-acids derived from hops (Humulus lupulus) by NMRMAGNETIC RESONANCE IN CHEMISTRY, Issue 9 2003Lars I. Nord Abstract Reduced forms of iso-,-acids (isohumulones), used in modern beer brewing were separated and characterized by 1H and 13C NMR spectroscopy. Components from mixtures of rho-iso-,-acids, tetrahydro-iso-,-acids, and hexahydro-iso-,-acids were isolated using high-performance liquid chromatography (HPLC) and analyzed by use of one- and two-dimensional NMR experiments. The data presented assign the identities of the main peaks in the HPLC traces for the reduced iso-,-acids. Previous tentative assignments regarding the cis and trans configurations and the structures of the acyl residues of the reduced iso-,-acids were confirmed and extensive NMR assignments were made. Furthermore, the previously unknown stereochemistry in the C-4 side-chain of the rho- and hexahydro-iso-,-acids was assigned. Copyright © 2003 John Wiley & Sons, Ltd. [source] 1H and 13C NMR assignments of abietane diterpenes from Aegiphila lhotzkyanaMAGNETIC RESONANCE IN CHEMISTRY, Issue 9 2003Maria Claudia Pinheiro Barros Abstract An NMR study of one new and several known abietane diterpenes isolated from the roots of Aegiphila lhotzkyana is described. In addition to 1D NMR, several 2D shift-correlated NMR pulse sequences (1H,1H-COSY, NOESY, HMQC and HMBC) were used to establish all the structures, and unambiguously perform the 1H and 13C chemical shift assignments of the new natural diterpene and three derivatives, the NMR data for which have not been reported previously. Revision of current data assignment for teuvincenone H is also suggested. Copyright © 2003 John Wiley & Sons, Ltd. [source] Structural determination and complete NMR spectral assignments of a new diterpenoid obtained from triptonide by biotransformationMAGNETIC RESONANCE IN CHEMISTRY, Issue 8 2003Lili Ning Abstract A new diterpenoid, 12,,13,-dihydroxytriptonide, was obtained from the transformed culture of triptonide by Catharanthus roseus cell suspension cultures. The complete 1H and 13C NMR assignments of the compound were carried out by using DEPT, COSY, HSQC, g-HMBC and NOESY techniques. Copyright © 2003 John Wiley & Sons, Ltd. [source] Complete 1H and 13C NMR assignments of three labdane diterpenoids isolated from Leonotis ocymifolia and six other related compoundsMAGNETIC RESONANCE IN CHEMISTRY, Issue 2 2003Ahmed A. Hussein Abstract Unambiguous and complete assignments of 1H and 13C NMR chemical shifts for three structurally complex labadane diterpenoids isolated from Leonotis ocymifolia (leonotin, leonotinin and nepetaefolin) and six other related compounds (hispanolone, 7,- and 7,-hispanols, marrubiin, villenol and andalusol), previously isolated from Labiatae species, are presented. The assignments are based on 2D shift-correlated [1H, 1H-COSY, 1H, 13C-gHSQC,1J(C,H), 1H,13C-gHMBC,nJ(C,H) (n = 2 and 3)] and DPFGSE 1D-NOE experiments. Copyright © 2003 John Wiley & Sons, Ltd. [source] Complete assignment of 1H and 13C NMR data for nine protopanaxatriol glycosidesMAGNETIC RESONANCE IN CHEMISTRY, Issue 7 2002Rongwei Teng Abstract Nine protopanaxatriol glycosides isolated from mild acid hydrolysis products of crude root saponins of Panax notoginseng were identified as 20(R)-ginsenoside-Rh1, 20(S)-ginsenoside-Rh1, ginsenoside-Rg1, -Re and -Rg2, notoginsenoside-R2 and -R1, a mixture of 25-hydroxy-20(S)-ginsenoside-Rh1 and its C-20 (R) epimer, ginsenoside-Rh4. The complete assignments of the 1H and 13C NMR chemical shifts for these glycosides were obtained by means of 2D NMR techniques, including 1H,1H COSY, ROESY, HMQC, HMBC and HMQC-TOCSY spectra. The glycosylation shift effect of protopanaxatriol and the differences in chemical shifts between 20(R)- and 20(S)-protopanaxatriol isomers are also discussed. Except for ginsenoside-Re and -Rg2, complete NMR assignments of the other seven glycosides are reported for the first time. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||