Secondary metabolites from the aerial parts of <Emphasis Type="Italic">Verbascum dudleyanum</Emphasis> and their biological activities

From the overground parts of Verbascum dudleyanum, six iridoid glycosides, aucubin, ajugol, catalpol, 6-O-α-L-rhamnopyranosylcatalpol, saccatoside, and 6-O-(3″-O-trans-p-coumaroyl)-α-L-rhamnopyranosylcatalpol, and two saponins, ilwensisaponin A and C, as well as a flavonoid, luteolin-7-O-β-glucopyranoside, together with an acetophenone glucoside, picein, were isolated. The structures of isolated compounds were elucidated by spectroscopic methods. These compounds showed biological acitivites. __________ Published in Khimiya Prirodnykh Soedinenii, No. 3, pp. 232–234, May–June, 2008.     

Chemistry of plants from Crete: stachyspinoside, a new flavonoid glycoside and iridoids from Stachys spinosa

The new flavonoid glycoside stachyspinoside (1), and the three iridoids, 7-O-acetyl-8-epi-loganic acid (2), ajugol (3) and harpagide (4) were isolated from Stachys spinosa. The structures of these compounds were established on the basis of mass spectrometry (ESMS and tandem MS), one- and two-dimensional nuclear magnetic resonance experiments (COSY, COSY LR, HMQC, TOCSY and HMBC) as well as simple chemical derivatization.     

A new polyoxygenated triterpene and two new aeginetic acid quinovosides from the roots of Rehmannia glutinosa

A new minor polyoxygenated triterpene named glutinolic acid (1) and two new aeginetic acid quinovosides (2, 3) were isolated from the roots of Rehmannia glutinosa LIBOSCH. (Scrophulariaceae) cultivated in Gunwi-gun, Korea. The structures of these compounds were established as 3α,19α,20β,24,30-pentahydroxyurs-12-en-28-oic acid (1, glutinolic acid), aeginetic acid 5-O-β-D-quinovoside (2) and aeginetoyl ajugol 5″-O-β-D-quinovoside (3) on the basis of chemical and spectroscopic evidence.     

A new carotenoid glycoside from Rehmannia glutinosa

A new carotenoid glycoside, namely neo-rehmannioside (1), together with five known compounds, 6-O-seco-hydroxyaeginetoyl ajugol (2), oxyrehmaionoside B (3), ajugol (4), geniposidic acid (5) and geniposide (6) was isolated from the 95% ethanol extract of dry roots of Rehmannia glutinosa. The structure of the new compound (1) was determined based on MS, IR, 1-D and 2-D NMR spectral data.     

Investigation of dynamic accumulation and regularity of nine glycosides and saccharides in Rehmannia glutinosa by rapid quantitative analysis technology

In the process of planting and harvesting of Rehmannia glutinosa, only the underground part is used, and a large number of stems and leaves that are considered non‐medicinal parts are usually discarded. Recent studies have shown that the chemical components in the leaves are similar to those identified in the roots. In this study, we selected leaves and roots from Rehmannia glutinosa at different growth stages and leaves from different cultivation regions to investigate the dynamic accumulation of three kinds of glycosides (catalpol, acteoside, and ajugol), six kinds of carbohydrates (rhamnose, fructose, sucrose, melibiose, stachyose, and verbascose), and acidic and neutral polysaccharides via rapid quantitative analysis technology, including ultra high performance liquid chromatography triple quadrupole tandem mass spectrometry, high‐performance liquid chromatography, and UV spectroscopy. The results showed that the Rehmannia glutinosa leaves also contained higher content of catalpol (3.81～24.51 mg/g), ajugol (0.55～10.23 mg/g), acteoside (1.34～21.16 mg/g), monosaccharide/ oligosaccharides (7.71～120.73 mg/g), and polysaccharides (5.63～15.57%). In this study, we developed a new rapid and simple method for determination to clarify the distribution and dynamic accumulation of nine glycosides and saccharides in Rehmannia glutinosa leaves to provide a scientific basis for the discovery, development, and utilization of the resource value of Rehmannia glutinosa leaves.     

Structure elucidation,complete NMR assignment and PM5 theoretical studies of new hydroxy‐aminoalkyl‐α,β‐unsaturated derivatives of the macrolide antibiotic josamycin

Four new hydroxy‐aminoalkyl derivatives of α,β‐unsaturated macrolide‐josamycin (2–5) have been synthesised and their structures have been studied by means of ¹H and ¹³C NMR and FT‐IR methods. Complete assignment of resonances in the ¹H and ¹³C NMR spectra has been made on the basis of ¹H? ¹³C HSQC, ¹H? ¹³C HMBC, ¹H? ¹H COSY, ¹H? ¹H NOESY 2D experiments. Spectroscopic data indicated that for the derivatives 3 and 4 some equilibrium between two different structures exists in contrast to derivatives 2 and 5. The lowest‐energy structures of the new derivatives of josamycin have been calculated and visualised by PM5 method at semi‐empirical level of theory, taking into account the NMR and FT‐IR data. The most significant differences between the structures of josamycin and its newly synthesised derivatives' were found in the conformation of the macrolide aglycone part and in the mutual orientation of the 4‐O‐isovalerylmycarosylmycaminose moiety relative to the aglycone part. PM5 semi‐empirical calculations indicated that the structures of the new macrolide derivatives are stabilised by rather weak intramolecular hydrogen bonds in agreement with spectroscopic data. Antimicrobial properties of the new derivatives 2–5 as well as those having an acetate group at C‐3 (6 and 7) were determined and compared to that of the parent macrolide antibiotic josamycin (1). Copyright © 2010 John Wiley & Sons, Ltd.     

The MX2Lx matrices,with M = Zn2+, Cd2+, Hg2+, X = Cl−, Br−, I− and L = pyrazine,quinoxaline, phenazine

Three structures combining the ditopic organic ligand quinoxaline with divalent metal halides MX₂, with M = Cd²⁺ and Hg²⁺, are reported. All three structures are coordination polymers, with the quinoxaline ligand acting as organic linker between metal centers. In two structures, with M = Hg²⁺ and X = Cl^? or Br^?, the formation of a 1-D, halide-bridged polymer in addition to the quinoxaline coordination polymer increases the dimensionality of the structure to 2-D, while in the case of M = Hg²⁺ and X = Cl^?, the formation of two halide-bridged polymers along with the coordination polymer results in the creation of a 3-D structure. Structural trends are identified, and the templating effect of the organic ligand is highlighted, through horizontal and vertical comparisons of these structures with related structures reported in the literature obtained upon combining the said metal halides with the related organic ligands pyrazine, quinoxaline, and phenazine, presented as the resulting matrices of structures.     

Structural revision of barlerin and acetyl barlerin

¹H- and ¹³C-NMR data as well as chemical evidence show that the structures of barlerin and acetyl should be corrected to 8-O-acetyl shanzhiside methylester and 6,8-di-O-acetyl-shanzshiside methylester, respectively.     

5-amino-2-methylpyridinium hydrogen fumarate: An XRD and NMR crystallography analysis

Single-crystal X-ray diffraction structures of the 5-amino-2-methylpyridinium hydrogen fumarate salt have been solved at 150 and 300 K (CCDC 1952142 and 1952143). A base–acid–base–acid ring is formed through pyridinium-carboxylate and amine-carboxylate hydrogen bonds that hold together chains formed from hydrogen-bonded hydrogen fumarate ions. ¹H and ¹³C chemical shifts as well as ¹⁴N shifts that additionally depend on the quadrupolar interaction are determined by experimental magic angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) and gauge-including projector-augmented wave (GIPAW) calculation. Two-dimensional homonuclear ¹H-¹H double-quantum (DQ) MAS and heteronuclear ¹H-¹³C and ¹⁴N-¹H spectra are presented. Only small differences of up to 0.1 and 0.6 ppm for ¹H and ¹³C are observed between GIPAW calculations starting with the two structures solved at 150 and 300 K (after geometry optimisation of atomic positions, but not unit cell parameters). A comparison of GIPAW-calculated ¹H chemical shifts for isolated molecules and the full crystal structures is indicative of hydrogen bonding strength.     

Manifestation of microgel-like particles of styrene-ethylene dimethacrylate copolymers in solution in 1H and 13C NMR spectra

From the integrated intensities of ¹H NMR bands it has been found that in solutions of styrene (St)-ethylene dimethacrylate (EDMA) copolymers, a considerable part of the monomer units do not show directly in high-resolution ¹H NMR spectra and it is suggested that these monomer units form compact structures, probably acting as cores of microgel-like particles. In ¹³C NMR spectra all monomer units are shown, including those which are part of the compact microgel structures. From a comparison of ¹H NMR spectra with other analytical methods (elemental analysis, infrared spectra) it follows that the composition of the copolymer in the core of the microgel is the same as the overall composition of the copolymer. The content of the compact structures in the microgel increases with the content of the EDMA component. The results are discussed from the point of view of structural features and of the motional restrictions of the St/EDMA copolymers in CCl₄ solution. The consequences for ¹H NMR analysis of copolymer composition are also discussed.     

Melamine–formaldehyde resins: Constitutional characterization by fourier transform 13C-NMR spectroscopy

The random chemical structures of melamine–formaldehyde resins, including methylated melamine–formaldehyde resins and urea–melamine formaldehyde resins, were investigated by ¹³C-NMR spectroscopy (Fourier transform). All the combined formaldehydes, methylol and methyl ether groups, methylene structures, and dimethylene ether structures were assigned. A ¹³C chemical shift of methylene carbon occurred by substitution of other constituents of the methylene group for a proton of the adjacent monosubstituted nitrogen atom, as shown in a ¹³C-NMR spectrum of urea–formaldehyde resins. It was found that the chemical shift of each corresponding carbon of both melamine resins and urea–melamine resins was almost superimposed with that of urea resins.     

Stable structures of 12-crown-O3N complexes with Li or Na in aqueous and acetonitrile solutions

Molecular geometries of crown ether derivatives play an important role in capturing and transporting alkali metal ions such as Li⁺ and Na⁺. As the selectivity of ions is observed in solutions, it is necessary to know their molecular structures in solutions. Recently, we investigated stable conformations of 12-crown-O₃N and its Li⁺ complex in aqueous solution by the combination of three programs, the CONFLEX, Gaussian 98, and BOSS programs. In the present study, we applied the same procedure to investigate stable structures of 12-crown-O₃N complexes with an alkali ion in aqueous and acetonitrile solutions. It was confirmed that the stable structures of Li⁺ and Na⁺ complexes in solutions are highly dependent on the polarity of the solvents.     

Structure and formation of [C4H6N]+ ions: 1—Ion structures derived from aliphatic nitriles

Structures and formation of the [C₄H₆N]⁺ ions present in the mass spectra of eleven α-substituted and eleven α-unsubstituted nitriles have been investigated from collisional activation and metastable ion spectra. Collisional activation spectra lead to identification of six structures. The [C₄H₆N]⁺ ions from some branched compounds prove to be mixtures. This, as well as the identity of all metastable ion parameters and certain spectral data, shows that energy differences between all structures are small. This is corroborated by MINDO/3 calculations showing a spread from 724 to 891 kJ mol^?1 over the structures. Earlier proposals for two different [C₄H₆N]⁺ ion structures, based on the mass spectra of deuterium labelled compounds, appeared to be correct. A computer program to calculate the contribution of standard spectra in a measured spectrum has been developed.     

Perfluorinated Dendrimers Based on Calix[4]arenes and Cyclam: Synthesis,Thermal Properties and Biological Activities

Four new dendritic structures carrying perfluorobenzyl bromide on the surface and calix[4]arene and cyclam as a core were synthesized by using the convergent approach. These structures were determined by ¹H-NMR, ¹³C-NMR and elemental analysis. Thermal stabilities of fluorinated dendritic structures were investigated using thermogravimetric analysis. Activation energies and thermal degradation of the structures were calculated with the Ozawa method. Thermogravimetric analysis of the dendritic structures reveals that the thermal stability of the structures increases with an increase in the number of the fluorine atoms. Dendritic structures synthesized were tested for their antimicrobial activity against, Salmonella typhimurium NRRLB, Micrococcus luteus, Pseudomonas aeruginosa, Enterococcus fecalis ATCC-29212, Bacillus cereus ATCC-117787, Klepsiella pneumoniae, Bacillus subtilis NRS-744 and Proteus vulgoris, Yersinia enterolitica, Saccharomyces cereviciae. The structures showed comparative activity against different strains of bacteria. Biological activities of the dendritic structures were seen to increase with an increase in fluorination and the number of nitrogen atoms.     

NMR Structure Determination of Saccharose and Raffinose by Means of Homo‐ and Heteronuclear Dipolar Couplings

Residual dipolar couplings have dramatically improved the accuracy and precision of high‐resolution NMR structures during the last years. This was first demonstrated for proteins. In this article, we describe, with raffinose and saccharose as examples, that dipolar couplings improve the precision of structures of carbohydrates for which usually very few structural parameters are available. The relative orientation as well as the dynamics of the monosaccharide moieties with respect to each other can be determined with the help of ¹³C,¹H and ¹H,¹H dipolar couplings, which can easily be measured. Significant differences between the solution and the X‐ray crystal structure exist. These results indicate that residual dipolar‐coupling data may provide a more complete and dynamic model of carbohydrates in particular, and small molecules in general.     

Solvent‐directed Regioselective Benzylation of Adenine: Characterization of N9‐benzyladenine and N3‐benzyladenine

The preferred sites for the benzylation of adenine under basic conditions were proven to be the N9 and N3 positions. Formation of the N9‐benzyladenine product is favored in polar aprotic solvents, such as DMSO, whereas the proportion of N3‐benzyladenine formed increases as the proportion of polar protic solvents, such as water, increases. X‐ray crystal structures were obtained for both N9‐benzyladenine and N3‐benzyladenine. ¹H‐¹³C HMBC NMR spectroscopy revealed diagnostic correlations used to assign the ¹H and ¹³C NMR chemical shifts confirming that the solution structures in three different solvents were the same as the isolated crystals. ¹³C NMR assignment for N9‐benzyladenine, N3‐benzyladenine, and N7‐benzyladenine was confirmed by computation using ADF.     

Amination and amidation of aryl iodides catalyzed by copper(I)-phenanthroline complexes

Four kinds of copper(I)-phenanthroline complexes ([Cu^I(phen)₂]Cl, [Cu^I(phen)Cl]₂, [Cu^I(phen)₂]BF₄, and Cu^I(phen)PPh₃Cl) were prepared and used as catalysts for amination and amidation of aryl iodide to investigate the influence on the yields of products due to differences of the structures. These complexes were found to work as catalysts on these reactions and showed that the differences of structures of copper(I) complexes significantly influenced the yield of aryl-nitrogen bond forming processes.     

Exploration of Carbon Allotropes with Four-membered Ring Structures on Quantum Chemical Potential Energy Surfaces

The existence of a new carbon allotrope family with four-membered rings as a key unit has been recently predicted with quantum chemical calculations. This family includes carbon allotropes in prism-, polymerized prism-, sheet-, tube-, and wavy-forms. An atypical bond property has been observed in this series of carbon structures, which differs from the typical sp³, sp², and sp hybridizations. The lowest energy barrier from some of the equilibrium states of the carbon structures has been determined with the SHS-ADDF (s caled-h ypersphere-s earch combined with the a nharmonic d ownward d istortion f ollowing) method within the GRRM software program package. The height of the barriers indicates that the well is deep enough for the carbon structures to exist. This class of carbon allotropes is expected to be energy-reservoirs with extra energy of 100–350 kJ mol⁻¹ per one carbon atom. This article presents the structures, energies and reactivity of the carbon allotropes with four-membered ring structures as well as the background of the findings in the context of the global exploration of potential energy surfaces. © 2018 Wiley Periodicals, Inc.     

稳定的气相二价阴离子C7H22-

采用HF, MP2, CCSD以及CISD方法,研究了二价阴离子C₇H₂^2-和C₇H₃^2-及其一价阴离子的几何结构振动频率。在理论上,我们得到了C₇H₂^2-和C₇H₃^2-能量最低结构分别为：C₂C(H₂)C₄^2-和C₂CHCHCHC₂^2-,而且均没有虚频。计算这两种结构所有可能的碎片化通道,碎片化能表明这两结构都不易解离为两个一价阴离子碎片。但是这两结构的垂直电离能和绝热电离能表明C₂C(H₂)C₄^2-是稳定的,但C₂CHCHCHC₂^2-是不稳定的。     

Probing DNA Mismatched and Bulged Structures by Using 19F NMR Spectroscopy and Oligodeoxynucleotides with an 19F‐Labeled Nucleobase

In this study, DNA local structures with bulged bases and mismatched base pairs as well as ordinary full‐matched base pairs by using ¹⁹F NMR spectroscopy with ¹⁹F‐labeled oligodeoxynucleotides (ODNs) were monitored. The chemical shift change in the ¹⁹F NMR spectra allowed discrimination of the DNA structures. Two types of ODNs possessing the bis(trifluoromethyl)benzene unit (F‐unit) at specified uridines were prepared and hybridized with their complementary or noncomplementary strands to form matched, mismatched, or bulged duplexes. By using ODN F1, in which an F‐unit was connected directly to a propargyl amine‐substituted uridine, three local structures, that is, full‐matched, G–U mismatch, and A‐bulge could be analyzed, whereas other structures could not be discriminated. A molecular modeling study revealed that the F‐unit in ODN F1 interacted little with the nucleobases and sugar backbone of the opposite strand because the linker length between the F‐unit and the uridine base was too short. Therefore, the capacity of ODN F1 to discriminate the DNA local structures was limited. Thus, ODN F2 was designed to improve this system; aminobenzoic acid was inserted between the F‐unit and uridine base so the F‐unit could interact more closely with the opposite strand. Eventually, the G‐bulge and T–U mismatch and the three aforementioned local structures could be discriminated by using ODN F2. In addition, the dissociation processes of these duplexes could be monitored concurrently by ¹⁹F NMR spectroscopy.