Four New Germine Esters from Veratrum dahuricum
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Abstract Four new alkaloids, compounds 1 – 4 , based on the germine (=4,9‐epoxycevane‐3,4,7,14,15,16,20‐heptol; 5 ) framework, were isolated from the rhizomes of V. dahuricum , together with germine proper. The X‐ray crystal structure of germine ( 5 ) was solved, and all compounds were characterized by circular dichroism, 1D‐ and 2D‐NMR ( 1 H, 1 H‐COSY, DEPT, HSQC, HMBC), as well as HR‐MS analyses.Keywords:
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Furanocoumarin
Apiaceae
Proton NMR
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The unambiguous assignment of NMR spectra of per-O-methylated 6-mono and 6,6-diamino-β-cyclodextrins
The step-by-step analysis of high-resolution proton and 13 C NMR spectra of per-O-methylated-6-monoamino and 6,6-diamino-A,D-β-cyclodextrins is described. Selected 2-D experiments (COSY, NOESY, HSQC, DEPT, and HMBC) allowed us to challenge the current interpretation. The full assignment of the proton and carbon-13 NMR spectra of these two compounds was performed enabling us to complete the assignment of NMR spectra acquired at 500 and 800 MHz for these important synthetic intermediates.Key words: COSY, NOESY, HSQC, DEPT, HMBC, NMR, 6-amino-β-cyclodextrins, 6,6-diamino-β-cyclodextrins.
DEPT
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Carbon-13 NMR satellite
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Aim To investigate the structure of mogroside IVa isolated from traditional Chinese medicine fructus momordicae [fruits of Siraitia grosvenori (Swingle) C. Jeffery] and summarize the NMR characteristics of the structure. Methods Cormnon extraction, separafion and purification methods were used. Various NMR techniques including ^1H NMR,^13C NMR, DEPT, ^1H-^1H COSY, HSQC, HMBC, NOESY and molecular model simulated by comtmter were used to elucidate the structure. Results ^1H and ^13C NMR signals of mogroside IVa were assigned, and spectroscopic basis was obtained for identification of such type of compounds. Conclusion 1D and 2D NMR techniques including ^1H-^1H COSY, HSQC, HMBC, NOESY spectra are powerful tools for structure analysis. The structure determined by NMR methods is identical with energy minimized conformation simulated by computer.
DEPT
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Four new (1–4), along with six known (5–10) dihydro-β-agarofuran sesquiterpene polyesters were isolated from the whole plants of Parnassia wightiana. The new compounds were structurally elucidated through spectroscopic analysis including UV (Ultraviolet Spectrum), IR (Infrared Spectrum), 1H-NMR (1Hydrogen-Nuclear Magnetic Resonance), 13C-NMR (13Carbon-Nuclear Magnetic Resonance), DEPT (Distortionless Enhancement by Polarization Transfer), 1H-1H COSY (1H-1H Correlation Spectroscopy), HSQC (Heteronuclear Single Quantum Coherence), HMBC (Heteronuclear Multiple Bond Correlation), NOESY (Nuclear Overhauser Enhancement Spectroscopy) and HR-MS (High Resolution Mass Specttrum) and their absolute configurations were proposed by comparison of NOESY spectra and specific optical rotations with those of known compounds and biosynthesis grounds. Compound 2 is the first sesquiterpene alkaloid isolated from this plant. New compounds 1–4 exhibited some cytotoxic activities against NB4, MKN-45 and MCF-7 cells at 20 μM and of which 4 showed the highest activity against NB4 and MKN-45 cells with inhibition rates of 85.6% and 30.5%, respectively.
Heteronuclear molecule
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Gradient-selected (gs) HSQC-NOESY type experiments are often applied in order to obtain NOE cross peaks in symmetrical molecules or in complex organic molecules, e.g. carbohydrates. Since the coherence-selecting gradients in these pulse sequences are separated by several delays, including the mixing time, the gs-HSQC-NOESY spectra exhibit severe signal attenuation due to diffusion effects. The respective NOE information unaffected by diffusion effects can be obtained by X-half-filtered gs-NOESY-HSQC spectra. In this paper, an X-half-filtered version of the gs-NOESY-HSQC experiment is presented and the NOE cross peak integrals of its spectra are compared with those of a standard gs-HSQC-NOESY experiment. With phenanthrene as an example of symmetrical molecules, it is shown that the relative signal attenuation of gs-HSQC-NOESY cross peaks versus gs-NOESY-HSQC cross peaks is caused by diffusion effects and follows the Stejskal-Tanner equation. In contrast, the X-half-filtered gs-NOESY-HSQC experiment provides NOE cross peaks with reasonable signal-to-noise ratios even for long-range interactions in the presence of quadrupolar relaxation. This is demonstrated by the spectra of lithium dimethylcuprate.
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The structures of 5 aldol reaction products were determined by 1D NMR spectroscopy(~1 H NMR、~(13) C NMR、DEPT) and 2D NMR spectroscopy (~1 H-~1 H COSY、HSQC、HMBC、~1 H-~1 H NOESY). All the ~1 H and ~(13) C NMR data were assigned, and the varieties of chemical shifts with the position of the substitute of the compounds were discussed.
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Carbon-13 NMR satellite
Aldol reaction
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Proton NMR
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In this study,some new oxazolidine derivatives were prepared from 1,4:3,6-dianhydro-D-fructose.Because of many same structural units in these compounds,the chemical environment of these compounds was extremely similar.The structures of these oxazolidines were evaluated with 1D and 2D NMR spectroscopy(1H NMR,13C NMR,DEPT-135,1H-1H COSY,HSQC,HMBC) and HRMS spectra.1H NMR and 13C NMR chemical shifts of these compounds were assigned.The stereochemistry of these compounds was established by the results obtained from X-ray crystal analysis of the relative compounds and NOESY spectroscopy.
DEPT
Chemical shift
Proton NMR
Chemical structure
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The sections in this article are 1 Introduction 2 HMQC(HSQC)–NOESY and NOESY–HMQC (HSQC) Experiments 3 Pulsed Field Gradient Methods 4 Sensitivity-Enhanced Versions of 3D Heteronuclear-Edited NOESY Experiments 5 Concluding Remarks 6 Biographical Sketches Related Articles
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Nuclear Overhauser effect
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