Structure elucidation and total assignment of 1H and 13C NMR data for a new bisdesmoside saponin from Cordia piauhiensis

Extensive 1D (¹H NMR, HBBD‐¹³C NMR, DEPT‐¹³C NMR) and 2D (COSY, TOCSY, NOESY, HMQC and HMBC) NMR analysis was used to characterize the structure of a new bisdesmoside saponin isolated from the methanol extract of stems of Cordia piauhiensis Fresen as 3β‐O‐[α‐L ‐rhamnopyranosyl‐(1 → 2)‐β‐D ‐glucopyranosyl]ursolic acid 28‐O‐[β‐D ‐glucopyranosyl‐(1 → 6)‐β‐D ‐glucopyranosyl] ester. Copyright © 2003 John Wiley & Sons, Ltd.     

Study of near‐symmetric cyclodextrins by compressed sensing 2D NMR

The compressed sensing NMR (CS‐NMR) is an approach to processing of nonuniformly sampled NMR data. Its idea is to introduce minimal l_p‐norm (0 < p ≤ 1) constraint to a penalty function used in a reconstruction algorithm. Here, we demonstrate that 2D CS‐NMR spectra allow the full spectral assignment of near‐symmetric β‐cyclodextrin derivatives (mono‐modified at the C6 position). The application of CS‐NMR ensures experimental time saving and the resolution improvement, necessary because of very low chemical shift dispersion. In the overnight experimental time, the set of properly resolved 2D NMR spectra required for the unambiguous assignment of mono(6‐deoxy‐6‐(1‐1,2,3‐triazo‐4‐yl)‐1‐propane‐3‐O‐(phenyl)) β‐cyclodextrin was obtained. The highly resolved HSQC spectrum was reconstructed from 5.12% of the data. Moreover, reconstructed 2D HSQC–TOCSY spectrum yielded information about the correlations within one sugar unit, and 2D HSQC–NOESY technique allowed the sequential assignment of the glucosidic units. Copyright © 2013 John Wiley & Sons, Ltd.     

Diketopiperazine Alkaloids from Penicillium spp. HS‐3, an Endophytic Fungus in Huperzia serrata

Cultivation of the fungus Penicillium spp. HS‐3, an endophytic fungus from the stems of Huperzia serrata, led to the isolation of a new diketopiperazine alkaloid, named as tryhistatin ( 1 ), together with three known ones, 2 – 4 , all of which share a similar backbone. The structure of 1 was established by detailed interpretation of the 1D‐ and 2D‐NMR spectra, and HR‐ESI‐MS data. Furthermore, 1D‐ and 2D‐NMR experiments were employed to elucidate the structure of 2 which was deduced previously only on the basis of the LC/MS method. In this article, we confirmed the correctness of the previously reported structure and made a complete assignment of the NMR signals of 2 for the first time.     

Iotroridoside‐A,a Novel Cytotoxic Glycosphingolipid from the Marine Sponge Iotrochota ridley

A new cytotoxic glycosphingolipid, Iotroridoside‐A, was isolated from the marine sponge Iotrochota ridley collected from the South China Sea near Hainan Island, China. On the basis of chemical degradation method and IR, MS, ¹H NMR, ¹³C NMR and 2D NMR spectrometry, its structure was assigned as 1‐O‐β‐D‐glucopyranosyl‐2‐[(4′ Z)‐2′‐hydroxytetracosene amido]‐4‐tetradecyl‐1, 3, 4‐butantriol. The new compound exhibits strong cytotoxicity against L1210 murine leukemia cells in vitro (ED₅₀ = 0.08 μg/mL).     

A New Alkaloid from the Seeds of Sophora alopecuroides L.

Alopecurin A, an alkaloid with an unprecedented skeleton, was isolated from the seeds of Sophora alopecuroides L. The absolute configuration and structure of this compound was identified as (3S,12R)‐3‐hydroxy‐1,7‐diazatricyclo[10.4.0.1^3,7]heptadecane‐11,16,17‐trione (=(7S,15aR)‐decahydro‐7‐hydroxy‐6H‐7,11‐methano‐4H‐pyrido[1,2‐a][1,7]diazacyclododecine‐4,15,16(12H)‐trione). The structure and absolute configuration was elucidated by spectroscopic methods, mainly HR‐ESI‐TOF‐MS, IR, 1D‐NMR (¹H‐ and ¹³C‐NMR), 2D‐NMR (COSY, NOESY, HSQC, HMBC), and particularly X‐ray crystal‐diffraction and CD spectral analysis.     

Phenolic Compounds from Formosan Euphorbia tirucalli

Fourteen polyphenolic compounds were isolated from the 60% aqueous acetone extract of Formosan Euphorbia tirucalli L. (Euphorbiaceae). Two compounds, 5‐desgalloylstarchyurin and 3,3′,4‐tri‐O‐methyl‐4′‐O‐rutinosyl ellagic acid, were deduced by concerted application of 1D and 2D NMR methods, and reassigned their NMR data.     

Total assignment of 1H and 13C NMR spectra of three triterpene saponins from roots of Silene vulgaris (Moench) Garcke

The assignments of ¹H and ¹³C NMR spectra for three new triterpene saponins from Silene vulgaris (gypsogenin 3‐O‐glucuronide, quillaic acid 3‐O‐glucuronide, and gypsogenin 3‐O‐glycoside) are reported. In addition to 1D NMR methods, 2D NMR techniques (COSY, HSQC, HMBC, and HSQC‐TOCSY) were used for the assignments. Copyright © 2002 John Wiley & Sons, Ltd.     

Spectral study of a new dihydroisocoumarin

A novel dihydroisocoumarin, 3,4‐dihydro‐6,8‐dihydroxy‐3‐(2′‐acetyl‐3′‐hydroxy‐5′‐methoxy)methyl‐1H‐[2]benzopyran‐1‐one, was isolated from the chloroform extract of the sap of the traditional herb Aloe vera. Its structure was determined by high‐resolution negative fast atom bombardment mass spectrometry (MS), 2D NMR spectroscopy and x‐ray crystallography. The molecular structure was elucidated by 2D NMR analysis. The complete assignment of the ¹H and ¹³C NMR spectra of this compound was performed by using ¹H detected one‐bond heteronuclear multiple quantum correlation (HMQC) and long‐range (two and three bonds) heteronuclear multiple quantum bond correlation (HMBC) experiments. Detailed analyses of the one‐ and two‐dimensional NMR techniques are presented in additional to the spectral properties (MS, IR and UV). Copyright © 2003 John Wiley & Sons, Ltd.     

(+)‐(14β)‐14‐Ethylmatridin‐15‐one,a New Quinolizidine Alkaloid from the Poisonous Plant Oxytropis ochrocephala Bunge

A new matrine alkaloid derivative (+)‐(14β)‐14‐ethylmatridin‐15‐one ( 1 ) was isolated from the poisonous plant Oxytropis ochrocephala Bunge . The structure was established by spectroscopic methods, including extensive 1D‐ and 2D‐NMR experiments.     

Two New N‐(O‐Carbamoylglucopyranosyl)‐N‐dimethylansamitocins from Actinosynnema pretiosum

Two new and a known N‐(O‐carbamoylglucopyranosyl)ansamitocins were isolated from Actinosynnema pretiosum ssp. auranticum ATCC 31565. The known N‐(4‐O‐carbamoyl‐β‐D ‐glucopyranosyl)‐N‐demethylansamitocin P 2 (=ACGP‐2; 1 ) was assigned according to 1D‐ and 2D‐NMR data, and the two new compounds were identified as N‐(6‐O‐carbamoyl‐β‐D ‐glucopyranosyl)‐N‐demethylansamitocin P 2 (=ACGP‐2′; 2 ) and N‐(4‐O‐carbamoyl‐β‐D ‐glucopyranosyl)‐N‐demethylansamitocin P 1 (=ACGP‐1; 3 ) on the basis of spectroscopic data interpretation including 2D‐NMR and tandem MS analysis.     

1H NMR discrimination of CHF4226.01 diastereoisomers in DMSO‐d6

Two diastereoisomers CHF4226.01 (R, R) and CHF4232.01 (S, R), differing for a chiral center, have been studied to investigate their possible discrimination using NMR. 1D NMR and 2D NMR experiments, such as COSY, NOESY and ROESY, were performed on pure isomers and on the association complexes formed in the presence of the chiral reagent (S)‐(?)‐1‐(2‐napthyl)ethylamine (S‐NEA). Moreover, computational studies, concerning conformational analysis and molecular dynamics, were started and supported the NMR results. Copyright © 2009 John Wiley & Sons, Ltd.     

DOSY NMR applied to analysis of flavonoid glycosides from Bidens sulphurea

2D DOSY ¹H NMR has proved to be a useful technique in the identification of the molecular skeleton of the four major compounds of ethyl acetate extract of aerial parts of Bidens sulphurea (Asteraceae). The combination of this technique with HPLC, mass spectrometry and other NMR techniques enabled the identification of four flavonoid glycosides: quercetin‐3‐O‐β‐D ‐galactopyranoside, quercetin‐3‐O‐β‐D ‐glycopyranoside, quercetin‐3‐O‐α‐L ‐arabinofuranoside and quercetin‐3‐O‐β‐D ‐rhamnopyranoside. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and Reactions of a New Quinone Quinoline 7‐(Carboxymethoxy)‐3‐sulfoquinoline‐5,6‐dione

The new ortho‐quinone quinoline 7‐(carboxymethoxy)‐3‐sulfoquinoline‐5,6‐dione was synthesized. The reaction of this quinoline‐5,6‐dione with hydroxylamine, hydrazine, phenylhydrazine, ethanol, semicarbazide, thiosemicarbazide, ethylenediamine, and benzene‐1,2‐diamine were studied. Ten new azaheterocyclic compounds were isolated and characterized by elemental analyses, IR, 1D NMR, 2D NMR, and MS spectra. Antioxidant activities of some obtained compounds were tested.     

Conformation and Topology of Diacylglycerol Kinase in E.coli Membranes Revealed by Solid‐state NMR Spectroscopy

Solid‐state NMR is a powerful tool for studying membrane proteins in a native‐like lipid environment. 3D magic angle spinning (MAS) NMR was employed to characterize the structure of E.coli diacylglycerol kinase (DAGK) reconstituted into its native E.coli lipid membranes. The secondary structure and topology of DAGK revealed by solid‐state NMR are different from those determined by solution‐state NMR and X‐ray crystallography. This study provides a good example for demonstrating the influence of membrane environments on the structure of membrane proteins.     

The Low Polar Constituents from Bidens Pilosa L. var. Minor (Blume) Sherff

Anew and 20 known compounds were isolated from Bidens pilosa L. var. minor (Blume) Sherff. The new compound was determined as 7‐phenyl‐hepta‐4,6‐diyne‐2‐ol by various physical techniques (MS, IR, UV, ¹H‐, ¹³C‐NMR, and 2D‐NMR).     

Diterpenoids from Diplopterygium rufopilosum

Two new diterpenoids, (3β,13S)‐3‐O‐[6‐O‐acetyl‐β‐D ‐glucopyranosyl]‐13‐O‐α‐L ‐rhamnopyranosyllabda‐8(17),14‐diene ( 1 ) and (4R,13S)‐18‐O‐β‐D ‐glucopyranosyllabda‐8(17),14‐dien‐13‐ol ( 2 ) have been isolated from the 95% EtOH extract of the dry fronds of Diplopterygium rufopilosum. Their structures were characterized by spectroscopic methods, including 1D‐NMR, 2D‐NMR, and HR‐ESI‐MS.     

Dynamic NMR study of cyclic derivatives of pyridoxine

A series of pyridoxine derivatives was investigated by ¹H and 2D nuclear overhauser enhancement spectroscopy (NOESY) NMR. The free energies of activation for the pyridyl‐oxygen rotation of the 2,4‐dinitrophenyl ether of the seven‐membered acetals of pyridoxine were measured by dynamic NMR. A conformational exchange between the chair and twist forms of the seven‐membered acetal ring was confirmed by dynamic NMR and STO3G computations. Copyright © 2014 John Wiley & Sons, Ltd.     

A Novel 19,21‐Secohetisan Diterpenoid Alkaloid from Aconitum tanguticum

A novel 19,21‐secohetisan diterpenoid alkaloid, tangutisine A ( 1 ), was isolated from Aconitum tanguticum (Maxim .) Stapf . Its structure was determined by HR‐EI‐MS and 1D‐ and 2D‐NMR spectroscopy and by comparison with the data of known 19,21‐secohetisan derivatives.     

A new coumarin from Perezia hebeclada

Methanol extracts from Perezia hebeclada roots yielded the new 8‐β‐D ‐glucopyranosyloxy‐4‐methoxy‐5‐methylcoumarin ( 1 ) together with the known 4‐β‐D ‐glucopyranosyloxy‐5‐methylcoumarin ( 2 ). Their structures were determined and verified, respectively, by MS and NMR studies, including 1D and 2D experiments. Two ¹³C NMR signals of the sugar residue of 2 were reassigned. Copyright © 2003 John Wiley & Sons, Ltd.     

Influence of feeding strategies of mixed microbial cultures on the chemical composition and microstructure of copolyesters P(3HB‐co‐3HV) analyzed by NMR and statistical analysis

NMR spectroscopy was applied for quantitative and qualitative characterization of the chemical composition and microstructure of a series of poly(3‐hydroxybutyrate‐co‐3‐hydoxyvalerate) copolymers, P(3HB‐co‐3HV), synthesized by mixed microbial cultures at several different feeding strategies. The monomer sequence distribution of the bacterially synthesized P(3HB‐co‐3HV) was defined by analysis of their high‐resolution 1D ¹³C NMR and 2D ¹H/¹³C HSQC and ¹H/¹³C HMBC NMR spectra. The results were verified by employment of statistical methods and suggest a block copolymer microstructure of the P(3HB‐co‐3HV) copolymers studied. Definitive distinction between block copolymers or a mixture of random copolymers could not be achieved. NMR spectral analysis indicates that the chemical composition and microstructure of the copolymers can be tuned by choosing a correct feeding strategy. Copyright © 2009 John Wiley & Sons, Ltd.