Complete 1H NMR spectral analysis of ten chemical markers of Ginkgo biloba

The complete and unambiguous ¹H NMR assignments of ten marker constituents of Ginkgo biloba are described. The comprehensive ¹H NMR profiles (fingerprints) of ginkgolide A, ginkgolide B, ginkgolide C, ginkgolide J, bilobalide, quercetin, kaempferol, isorhamnetin, isoquercetin, and rutin in DMSO‐d₆ were obtained through the examination of 1D ¹H NMR and 2D ¹H,¹H‐COSY data, in combination with ¹H iterative full spin analysis (HiFSA). The computational analysis of discrete spin systems allowed a detailed characterization of all the ¹H NMR signals in terms of chemical shifts (δ_H) and spin‐spin coupling constants (J_HH), regardless of signal overlap and higher order coupling effects. The capability of the HiFSA‐generated ¹H fingerprints to reproduce experimental ¹H NMR spectra at different field strengths was also evaluated. As a result of this analysis, a revised set of ¹H NMR parameters for all ten phytoconstituents was assembled. Furthermore, precise ¹H NMR assignments of the sugar moieties of isoquercetin and rutin are reported for the first time. Copyright © 2012 John Wiley & Sons, Ltd.     

NMR spectra of paramagnetic complexes of 1-vinylimidazole with iron group metals

The high-resolution ¹H and ¹³C NMR spectra of 1-vinylimidazole complexes with iron group metals were recorded. The contact coupling in these systems was established in the ¹H and ¹³C NMR spectra. The applicability of the NMR spectra transformed by long-range hyperfine coupling for elucidating the molecular structure of the ligand was shown. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1430–1433, June, 2005.     

1-Methylthio-1-phenyl-1-silacyclohexane: Synthesis,conformational preferences in gas and solution by GED,NMR and theoretical calculations

1-Methylthio-1-phenyl-1-silacyclohexane 1, the first silacyclohexane with the sulfur atom at silicon, was synthesized and its molecular structure and conformational preferences studied by gas-phase electron diffraction (GED) and low temperature ¹³C and ²⁹Si NMR spectroscopy (LT NMR). Quantum-chemical calculations were carried out both for the isolated species and solvate complexes in gas and in polar medium. The predominance of the 1-MeS_axPh_eq conformer in gas phase (1-Ph_eq:1-Ph_ax = 55:45, ΔG° = 0.13 kcal/mol) determined from GED is consistent with that measured in the freon solution by LT NMR (1-Ph_eq:1-Ph_ax = 65:35, ΔG° = 0.12 kcal/mol), the experimentally measured ratios being close to that estimated by quantum chemical calculations at both the DFT and MP2 levels of theory.     

Comprehensive 1H and 13C NMR assignment of 13 protobassic acid saponins

This study aimed to carry out complete ¹H and ¹³C NMR assignment of 13 protobassic acid saponins, including arganins A–C ( 1 – 3 ) and F ( 4 ), butyrosides B–D ( 5 – 7 ), tieghemelin ( 8 ), 3′-O-glucosyl-arganin C ( 9 ), Mi-saponins A–C ( 10 – 12 ), and mimusopsin ( 13 ), recorded in methanol-d₄. This was accomplished by the analysis of high-resolution one-dimensional (1D) NMR (¹H and ¹³C), two-dimensional (2D) NMR (¹H–¹H COSY, HSQC, and HMBC), and selectively excited 1D TOCSY spectra. Before this study, ¹H and ¹³C NMR data of arganins A–C ( 1 – 3 ) and F ( 4 ) were partially assigned. Our effort leads to their complete assignment, especially the glycon residue, and revises some reported data. Some revisions of the ¹H and ¹³C NMR data in the glycon part of butyroside C ( 6 ), tieghemelin ( 8 ), Mi-saponin A ( 10 ), and mimusopsin ( 13 ) were made. Those data of butyrosides B and D ( 5 & 7 ) and Mi-saponin B ( 11 ), which had not been recorded in methanol-d₄, are provided. In addition, the ¹H and ¹³C NMR data of Mi-saponin C ( 12 ) are reported for the first time. These data, being recorded in methanol-d₄, should be more friendly for use as a reference for identifying the related triterpenoid saponins.     

1H and 13C NMR spectra of Strychnos alkaloids: Selected NMR updates

The PBE0/pcSseg-2//pcseg-2 calculations of ¹H and ¹³C NMR chemical shifts were performed for a classical series of 12 Strychnos alkaloids (except for the earlier studied parent strychnine), namely akuammicine, isostrychnine, rosibiline, tsilanine, spermostrychnine, diaboline, cyclostrychnine, henningsamide, strychnosilidine, strychnobrasiline, holstiine, and icajine. It was found that the calculated ¹H and ¹³C NMR chemical shifts show markedly good correlations with available experimental data, as characterized by a mean absolute error of 0.22 ppm for the range of 8 ppm for protons and 1.97 ppm for the range of 180 ppm for carbons. Complementarily, the present results provide essential NMR update and fill a gap in the NMR data of this distinguished group of vitally important natural products.     

1-烷基-1'-乙酰基二茂铁的合成

用新方法合成了1-烷基-1'-乙酰基二茂铁, 该法与传统方法相比易于得到单一产物. 通过7种1-烷基二茂铁甲酸与三氯化磷作用形成酰氯, 再与乙酰乙酸乙酯的钠盐进行反应, 皂化脱羧得到1-烷基-1'-乙酰基二茂铁化合物, 用元素分析、红外光谱、核磁共振氢谱确定了化合物的结构.     

1H and 13C NMR assignments of abietane diterpenes from Aegiphila lhotzkyana

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.     

Quantitative 1H NMR analysis of reacted silanol groups in silica nanoparticles chemically modified with monochlorosilanes

Quantitative analysis of reacted silanol groups in silica nanoparticles modified chemically with monochlorosilanes was performed by ¹H NMR after treatment with cesium fluoride. Silica nanoparticles were modified chemically by the reaction between the silanol groups and monochlorosilanes, and the structure of the organic moiety anchored onto the silica surface was confirmed with solid‐state ¹³C NMR. As monochlorosilanes react with silanol groups at 1:1 ratio unlike di‐ or trichlorosilanes, the number of the silanes introduced into silica nanoparticles equals that of reacted silanol groups. Organically modified silica nanoparticles were dissolved using cesium fluoride, and the amount of the soluble organic compounds originated from the introduced silanes was determined by a ¹H NMR internal standard method using pyrene as the reference. Those values determined by ¹H NMR were in good agreement with those determined by elemental analysis. Thus, the number of reacted silanol groups per one particle was calculated on the basis of the results obtained by the ¹H NMR method, and the values were highly dependent on the steric structure of the introduced silanes. Copyright © 2010 John Wiley & Sons, Ltd.     

1H and 13C NMR Assignments for a 27-Norolean-13-en-3-hydroxy-28-oic Acid Glycoside from Isertiahaenkeana

A nortriterpene glycoside, pyrocincholic acid 3β-O-β-6-deoxy-D-glucopyranoside-28-O-β-D-glucopyranoside, was isolated from the leaves of Isertia haenkeana and its structure established by ¹H and ¹³C NMR spectral studies. The complete ¹H and ¹³C NMR resonance assignments for this triterpene were confirmed by the conventional 1D NMR methods and 2D shift-correlated NMR techniques: DQF COSY, TOCSY, ROESY and HMQC.     

Synthesis and Biological Activities of O-Alkyl,O-Aryl,O-{Z-[1-Phenyl-2-(1H-1,2,4-triazol-1-yl)ethylidene]amino} Phosphorothioates

A series of title compounds 2 were efficiently synthesized via the condensation of 1-phenyl-2-(1H-1,2,4-triazol-1-yl)ethanone oxime with various asymmetric thiophosphoryl chlorides in sodium hydroxide powder and acetonitrile system. The structures of title compounds 2 were confirmed by IR, ¹H NMR, ³¹P NMR, EI-MS, and elemental analysis. The results of preliminary bioassays indicated that the title compounds 2 possessed good to moderate insecticidal activity against aphides at the dosage of 250 mg/L, and some of them exhibited moderate fungicidal activities at the concentration of 100 mg/L.     

Complete assignment of 1H and 13C NMR data of pravastatin derivatives

The complete ¹H and ¹³C NMR data of 27 pravastatin derivatives are presented. Assignment was achieved by use of 1D and 2D NMR experiments (selective 1D NOE, COSY, NOESY, HSQC, HMBC). Copyright © 2008 John Wiley & Sons, Ltd.     

Charakterisierung der Protonen in polykristallinen Parawolframaten durch 1H‐MAS‐NMR‐Untersuchungen

Characterization of the Protons in Polycrystalline Paratungstates using ¹H MAS NMR Investigations ¹H MAS NMR experiments are used to characterize the non‐acid protons of the anions in polycrystalline paratungstates by means of the measured isotropic chemical shift values. The investigation of various hydrates of ammonium paratungstate allows a direct proof of protons in NH₄ ions and in water molecules while protons of the anions are not detectable. However, for both the potassium and the sodium paratungstates ¹H MAS NMR investigations detected the protons of water molecules and the non‐acid protons of the paratungstate anions. Additional ¹H broad‐line NMR experiments at 173 K support the interpretation of the results obtained by the ¹H MAS NMR investigations. For the NMR signal of the non‐acid protons of the paratungstate anion in the ¹H MAS NMR spectra of the potassium salt line‐splitting appears. This refers to the existence of two nonidentical positions of the protons in the crystal lattice and is in agreement with the results of the X‐ray structural analysis.     

Detailed assignments of 1H and 13C NMR spectral data of 14 cyclopentane derivatives

Detailed assignments of ¹H and ¹³C NMR spectral data for 14 cyclopentane derivatives are reported. The assignments are based on 1D ¹H and ¹³C NMR and on 2D shift‐correlated [¹H, ¹³C‐HMQC], J‐resolved and NOEDIF experiments. Copyright © 2003 John Wiley & Sons, Ltd.     

1H, 13C, 19F and 11B NMR spectral reference data of some potassium organotrifluoroborates

Complete ¹H, ¹³C, ¹⁹F and ¹¹B NMR spectral data for 28 potassium organotrifluoroborates are described. The resonance for the carbon bearing the boron atom is described for most of the studied compounds. A modified ¹¹B NMR pulse sequence was used and better resolution was observed allowing the observation of ¹¹B–¹⁹F coupling constants for some of the studied compounds. Copyright © 2009 John Wiley & Sons, Ltd.     

QSAR studies of phenylhydrazine-substituted tetronic acid derivatives based on the 1H NMR and 13C NMR chemical shifts

The quantitative structure–activity relationship models of 40 phenylhydrazine-substituted tetronic acid derivatives were established between the ¹H nuclear magnetic resonance (NMR) and ¹³C NMR chemical shifts and the antifungal activity against Fusarium graminearum, Botrytis cinerea, Rhizoctonia cerealis, and Colletotrichum capsici. The models were validated by R, R², R_A², variance inflation factor, F, and P values testing and residual analysis. It was concluded from the models that the ¹³C NMR chemical shifts of C8, C10, C7, and the ¹H NMR chemical shifts of Ha contributed positively to the activity against Fusarium graminearum, Botrytis cinerea, Colletotrichum capsici, and Rhizoctonia cerealis, respectively. The models indicated that decreasing the election cloud density of specific nucleuses in compounds, for example, by the substituting of electron withdrawing groups, would improve the antifungal activity. These models demonstrated the practical application meaning of chemical shifts in the quantitative structure–activity relationship study. Furthermore, a practical guide was provided for further structural optimization of the antifungal phenylhydrazine-substituted tetronic acid derivatives based on the ¹H NMR and ¹³C NMR chemical shifts.     

The 1H and 13C NMR chemical shifts of Strychnos alkaloids revisited at the DFT level

The density functional theory calculation of ¹H and ¹³C NMR chemical shifts in a series of ten 10 classically known Strychnos alkaloids with a strychnine skeleton was performed at the PBE0/pcSseg-2//pcseg-2 level. It was found that calculated ¹H and ¹³C NMR chemical shifts provided a markedly good correlation with experiment characterized by a mean absolute error of 0.08 ppm in the range of 7 ppm for protons and 1.67 ppm in the range of 150 ppm for carbons, so that a mean absolute percentage error was as small as ~1% in both cases.     

Stereochemicai study of 7-aryl-1,7,8,8a-tetrahydro-3(2H)indolizinones by1H and13C NMR

Stereochemistry of 7-aryl-1,7,8,8a-tetrahydro-3(2H)-indolizinones was studied by¹H and¹³C NMR. Complete assignment of¹H NMR signals and analysis of¹H-¹H coupling constants were performed using the iterative PANIC program. Values of³ J _6,7,³ J _7,8endo, and⁴ J _5,7 allow one to unambiguously identify the correspondingexo- andendo-stereoisomers. For stereoisomers with exo-orientation of H(7), complete assignment of¹³C NMR signals was performed on the basis of analysis of the¹³C-¹H coupling constants using two dimensional heteronuclear shift-correlating spectroscopy.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 591–593, March, 1996.     

NMR analysis of mono‐ and difructosyllactosucrose synthesized by 1F‐fructosyltransferase purified from roots of asparagus (Asparagus officinalis L.)

Two novel oligosaccharides, mono‐ and difructosyllactosucrose {[O‐β‐D ‐fructofuranosyl‐(2 → 1)]_n‐β‐D ‐fructofuranosyl‐O‐[β‐D ‐galactopyranosyl‐(1 → 4)]‐α‐D ‐glucopyranoside, n = 1 and 2} were synthesized using 1^F‐fructosyltransferase purified form roots of asparagus (Asparagus officinalis L.). Their ¹H and ¹³C NMR spectra were assigned using several NMR techniques. The spectral analysis was started from two anomeric methines of aldose units, galactose and glucose, since they showed separate characteristic signals in their ¹H and ¹³C NMR spectra. After assignments of all the ¹H and ¹³C signals of two units of aldose, they were discriminated as galactose and glucose using proton–proton coupling constants. The HMBC spectrum revealed the galactose residue attached to C‐4 of glucose, fructose residue attached to the C‐1 of glucose, and further fructosyl fructose linkage extended from the glucosyl fructose residues. Copyright © 2002 John Wiley & Sons, Ltd.     

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.     

1H‐19F REDOR‐filtered NMR spin diffusion measurements of domain size in heterogeneous polymers

Solid state NMR spectroscopy is inherently sensitive to chemical structure and composition and thus makes an ideal method to probe the heterogeneity of multicomponent polymers. Specifically, NMR spin diffusion experiments can be used to extract reliable information about spatial domain sizes on multiple length scales, provided that magnetization selection of one domain can be achieved. In this paper, we demonstrate the preferential filtering of protons in fluorinated domains during NMR spin diffusion experiments using ¹H‐¹⁹F heteronuclear dipolar dephasing based on rotational echo double resonance (REDOR) MAS NMR techniques. Three pulse sequence variations are demonstrated based on the different nuclei detected: direct ¹H detection, plus both ¹H?¹³C cross polarization and ¹H?¹⁹F cross polarization detection schemes. This ¹H‐¹⁹F REDOR‐filtered spin diffusion method was used to measure fluorinated domain sizes for a complex polymer blend. The efficacy of the REDOR‐based spin filter does not rely on spin relaxation behavior or chemical shift differences and thus is applicable for performing NMR spin diffusion experiments in samples where traditional magnetization filters may prove unsuccessful. This REDOR‐filtered NMR spin diffusion method can also be extended to other samples where a heteronuclear spin pair exists that is unique to the domain of interest.