共查询到20条相似文献,搜索用时 31 毫秒
1.
The structure of galactomannans isolated from seeds of G. delavayi and G. aquatica was studied by 1H and 13C NMR spectroscopy. It was found that the galactomannans consisted mainly of β-1-4-bound mannopyranoses, a part of which was substituted on the C-6 hydroxyl by terminal units of α-galactopyranose.__________Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 12–13, January–February, 2005. 相似文献
2.
The structures of two novel steroidal derivatives (1 and 4) were elucidated. Steroidal derivatives namely fologenin (1) and hoyagenin (4) have been isolated from chloroform-soluble extract of the whole plant of Hoya longifolia (family: Asclepiadaceae), and their structures were determined by using 1H NMR, 13C NMR, 1H–1H COSY and FAB-MS techniques as well as chemical degradation and derivatisation. 相似文献
3.
M. Dračínský R. Pohl L. Slavětínská H. Hřebabecký M. Buděšínský 《Tetrahedron: Asymmetry》2011,22(18-19):1797-1808
Cyclic five-membered ring sulfoxides and sulfones were prepared by a stepwise in situ oxidation of the corresponding sulfides with meta-chloroperbenzoic acid in an NMR tube. The oxidation was followed by NMR and both 1H and 13C NMR data were collected. The geometries of all of the compounds were optimized using the DFT B3LYP/6-31G7 method and the 13C and 1H chemical shifts were calculated for geometry-optimized structures with the DFT B3LYP/6-31++G7 method. The calculated 13C chemical shifts induced by oxidation (Δδ values) were in very good agreement with the experimental data and could be used to determine the oxidation state of the sulfur atom (–S–, –SO–, –SO2–). The characteristic differences of the induced oxidation chemical shifts of the carbon atoms in the α-position and β-position to sulfur were successfully used to distinguish between the diastereoisomeric sulfoxides and allowed configuration determination. 相似文献
4.
Abstract The syntheses of octyl β-D-glucopyranoside-GABA and GABOB conjugates are presented. The selectively protected octyl-β-D-glucopyranoside and γ-aminobutyric acids were coupled with N, N'-dicyclohexylcarbodiimide. 1H and 13C NMR spectroscopy were used to verify the proposed structures. 相似文献
5.
Qingchao Liu Zheng Fan Dong Li Wenhong Li Tiantian Guo 《Journal of carbohydrate chemistry》2013,32(8-9):386-402
Facile synthesis of the natural oleanane-type triterpenoid saponin 1 isolated from Panax japonicus C. A. Meyer var major (Burk.) C. Y. Wu et K. M. Feng and its derivatives is reported. The glucuronide residue in saponins at a later stage via TEMPO-mediated oxidation of the primary-OH has been achieved. All structures of new compounds were established by means of 1H NMR, 13C NMR, HRMS, and optical rotation. 相似文献
6.
Hedyotis caudatifolia Merr. et Metcalf. (HC), a folk medicine in Yao nationalities areas in China, was used to investigate the chemical constituents. Through silica gel and Sephadex LH-20 column chromatography, nine compounds were isolated and purified. By physical and chemical properties, IR, MS (EI-MS, high resolution EI-MS), 1D NMR (1H NMR, 13C NMR) and 2D NMR (HSQC, 1H–1H COSY, HMBC), their structures were identified as β-sitosterol (1), stigmasterol (2), scopolin (3), 2-hydroxy-1,7,8-trimethoxyanthracene-9,10-dione (4), oleanolic acid (5), ursolic acid (6), methyl barbinervate (7), β-daucosterol (8) and p-Hydroxybenzoic acid (9). These compounds were isolated from HC for the first time, and 4 a new anthraquinone whose biological activities are worth to be investigated in future. These compounds may contribute to the HC’s pharmacological effects on treating diseases, and may be used as candidates for control index in establishing the quality control standard of HC. 相似文献
7.
A polysaccharide of Thea sinensis, TSA, has been isolated from the fresh leaves as a major fraction of polysaccharides. The mol. wt. was estimated to be 850,000 with [α]D15 + 25.5° (c=0.75, H2O). The component sugars were determined as L-rhamnose, L-arabinose, and D-galactose in molar ratio of 0.54: 1.0: 0.94. The O-acetyl groups locating on galactose residues position 2 were also identified and the content was 3.8%. The 13C NMR spectrum and CrO3 oxidation of TSA indicated the Rhamnose, Arabinose and Galactose to be in α-, α- and β-configurations, respectively. Methylation analysis, periodate oxidation, partial hydrolysis and 13C NMR spectrum showed that TSA is a branched galactoarabinan. 相似文献
8.
Esmail Vessally Ladan Edjlali Maryam Saber Soma Aryana 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(5):791-797
Geometrical structures, Hammett constants, 1H and 13C chemical shift values, molecular electrostatic potential maps, and several thermodynamic parameters of α-acyloxy carboxamide
derivatives (4a–o) were calculated using HF and DFT/B3LYP methods with 6-31G(d) basis set. The optimized structures were compared with analogous compound. The 1H and 13C NMR shielding tensors were computed with the Gauge-Independent Atomic Orbital (GIAO) method. Comparison of the experimental
1H and 13C NMR chemical shifts of 4a–o molecules with the theoretical data indicates good agreement. 相似文献
9.
Shazia Anjum Muhammad Asif Kashaf Zia Bakhat Jahan Muhammad Ashraf Shafqat Hussain 《Natural product research》2020,34(16):2315-2318
Abstract The present work deals with the biological and phytochemical studies on Capparis decidua (Forssk) Edgew from Cholistan desert of Pakistan. Aerial and floral parts of C. decidua were collected and dried under shade. Powdered materials of each part of C. decidua were extracted with methanol separately, followed by phytochemical studies. Hexane fraction of aerial parts of the C. decidua obtained after solvent-solvent extraction was purified through repeated column chromatography by increasing order of polarity. Four compounds were purified and identified as simiarenol (1), lupeol (2), taraxerol (3) and β-sitosterol (4). Simiarenol and lupeol were isolated for the first time from genus Capparis. The structures of these compounds were established by comparing the spectroscopic data (1H NMR, 13C NMR, IR, UV & Mass spectrometry) reported in literature. The structure of 1 was further confirmed by XRD analysis. Anti-bacterial activities of crude methanolic extracts were determined against 13 bacterial strains (MIC 250-1000?μg/mL). α-Glucosidase and urease inhibitory activities of pure compounds were also determined. Compounds 1, 2 and 4 showed α-glucosidase inhibition with IC50 at 96.12?±?0.12, 65.28?±?0.13 and 128.14?±?0.17?μM, respectively. 相似文献
10.
11.
Z. Györgydeák W. Holzer R. W. Kunz A. Linden 《Monatshefte für Chemie / Chemical Monthly》1995,126(6-7):733-746
Summary Treatment of aromatic carbaldehyde (diaminomethylene)hydrazones1 with hot acetic anhydride or benzoyl chloride affords 1,4-diacyl-3-acylamino-5-aryl-4,5-dihydro-1H-1,2,4-triazoles2. In contrast, a new type of 0,N-acetal with an 1,2,4-triazole substructure (3) is obtained from 4-pyridine-carbaldehyde (diaminomethylene)hydrazone (li) by using a similar reaction procedure. The structures of all novel compounds were confirmed by spectroscopic data (1H and13C NMR, MS, IR); some representative compounds were also studied by X-ray analysis.Dedicated to Professor Dr.S. Makleit on the occasion of his 65th birthday. 相似文献
12.
Abstract Glycosidation of 2′ 3′ 6′-tri-O-benzyl-α-d-glucopyranosyl 2,3-di-O-benzyl-4,6-O-benzylidene-α-d- glucopyranoside (2) with α-aceto-bromosophorose (1) gave the α- and β-linked tetrasaccharides 3 and 4 in an approximately 2:1 ratio in dichloromethane or acetonitrile. The reaction is discussed, notably the predominant formation of α-glycosides. Both compounds were fully characterized by 1H and 13C NMR spectroscopy applying 1D TOCSY, 1D T-ROESY, 1H-detected one-bond and multiple bond 1H, 13C 2D COSY. Deprotection of 3 and 4 furnished the free sophorosyl trehaloses 7 and 8. 相似文献
13.
Zhiping Wu Yu Chen Xu Feng Bing Xia Ming Wang Yunfa Dong 《Chemistry of Natural Compounds》2009,45(6):829-833
Two new ceramides were isolated from the bulbs of Zephyranthes candida. Their structures were established as (2S,3S,4R,13E)-1,3,4-trihydroxy-2-[(2′R)-2′-hydroxytetracosanoylamino]-13-octadecene, named zephyranamide A (1) and (2S,3S,4R)-1,3,4-trihydroxy-2-octacosanoylaminohexadecene, named zephyranamide B (2). The structures of the new compounds were elucidated by spectral techniques including 1H NMR, 13C NMR, as well as HSQC, HMBC, DEPT, and COSY. 相似文献
14.
Cyclic six-membered ring sulfoxides and sulfones were prepared by a stepwise in situ oxidation of the corresponding sulfides with meta-chloroperbenzoic acid in an NMR tube. The oxidation was followed by NMR spectra and the 1H and 13C NMR data were collected. The geometries of all of the compounds were optimized using the DFT B3LYP/6-31G∗∗ method and the 13C and 1H NMR chemical shifts were calculated for geometry-optimized structures with the DFT B3LYP/6-31++G∗∗ method. The calculated 13C NMR chemical shifts induced by oxidation (Δδ values) are in very good agreement with the experimental data and can be used to determine the oxidation state of the sulfur atom (-S-, -SO-, -SO2-). The characteristic differences of the induced oxidation chemical shifts of carbon atoms at the α- and β-position to sulfur were successfully used for distinguishing between the diastereoisomeric sulfoxides. 相似文献
15.
Shiwani Berry Shamsher S. Bari Pooja Yadav Ankita Garg Sadhika Khullar Sanjay K. Mandal 《合成通讯》2020,50(19):2969-2980
Abstract An efficient protocol for the stereoselective synthesis of pyrazolo[5,1-b]thiazole-3-carboxylate tethered β-lactam conjugates 8a–j from novel pyrazolo [5,1-b]thiazole-3-carboxylate substituted Schiff’s bases 6a–f is reported here. The reaction between various ketene precursors and novel Schiff’s bases 6a–f afforded exclusive formation of trans-β-lactams 8a–j. The substrate scope of this approach was investigated extensively by varying different groups (R, Z). All the novel compounds were characterized using various spectroscopic techniques, such as FT-IR, 1H NMR, 13C NMR, elemental analysis, 13C NMR (DEPT-135), and mass spectrometry in representative cases. Single crystal X-ray crystallographic study of trans-ethyl 7-(1-(4-methoxyphenyl)-4-oxo-3-phenoxyazetidin-2-yl)-6-methyl-2-(methylthio)pyrazolo[5,1-b]thiazole-3-carboxylate 8a has confirmed the molecular structure and the stereochemical outcome. To the best of our knowledge, the synthesis of such types of Schiff’s bases and β-lactam conjugates has not been reported so far. 相似文献
16.
Three fructans (CoPS1, CoPS2 and CoPS3) were isolated from the root of Cyathula officinalis Kuan, a traditional Chinese medicine. The structures of the fructans were determined by methylation, reductive-deavage method combined with GC-MS analysis, and 13C NMR spectroscopy. These results show that the fructans (CoPS1, CoPS2 and CoPS3) are graminan type fructans, and comprised of (2→t)- and (2→6)-linked β-D-fructofuranosyl backbone residues containing high branches. 相似文献
17.
Abstract Selective acetolysis of primary benzyl ethers of O-benzyl C-glucosides has been investigated. β-anomers were shown to give fully acetylated compounds, while the α-anomers remained unchanged under the same conditions. The products were assigned by IR, 1H NMR, 13C NMR, and EI-MS. 相似文献
18.
《Journal of Coordination Chemistry》2012,65(7):1076-1085
Planar [Ni(bedtc)(PPh3)Cl] (1), [Ni(bedtc)(PPh3)(NCO)] (2), [Ni(bedtc)(PPh3)(NCS)] (3), [Ni(bedtc)(PPh3)(CN)] (4) and [Ni(bedtc)(dppe)]ClO4 (5) (where bedtc = N-benzyl-N-(2-hydroxyethyl)dithiocarbamate anion, PPh3 = triphenylphosphine and dppe = 1,2-bis((diphenylphosphino)ethane)) were prepared from [Ni(bedtc)2]. Complexes 1–5 were characterized by elemental analysis, electronic, IR and NMR (1H, 13C, and 31P) spectra. Electronic spectra of the complexes show bands corresponding to dz 2 → dxy/dx 2 ? y 2 transitions. The complexes were diamagnetic. IR and 13C NMR studies indicate the mesomeric flow of π-electron density from the dithiocarbamate towards the nickel. In 1H NMR, α-CH2–and β-CH2–protons of–CH2–CH2–OH were equally deshielded. The deshielding for the coordinated phosphorus signals in 31P NMR spectra for all the cases compared with the free phosphine clearly manifests the drift of electron density from the phosphorus toward the metal on complexation. Single crystal X-ray structures of 1–3 indicate that nickel is in a planar environment with short >S2C–N bond distances. In 2, a rare mode of coordination between nickel and cyanate (NCO?) through the nitrogen is observed. Significant asymmetry in Ni–S bond distances were observed for 1–3 clearly supporting the trans influences of Cl?, NCO? and NCS?, respectively, over PPh3. 相似文献
19.
《Journal of Coordination Chemistry》2012,65(3):425-432
Abstract A novel dioxime, 1,2 dihydroxyimino-3,7-diaza-9,10-O-benzaloctane (LH2) was prepared by reaction of l,2-0-benzylidene-4-aza-7-aminoheptane and anti-phenylchloroglyoxime in absolute ethanol. Mononuclear complexes with a metal-ligand ratio of 1:2 were prepared with Co(II), Cu(II) and Ni(II). To elucidate the structures of the ligand and complexes, elemental analyses, IR, 1H NMR and 13C NMR spectral data and magnetic susceptibility measurements have been examined. 相似文献
20.
James M. Riordan Philip E. Morris Jr. Donald E. Kiely 《Journal of carbohydrate chemistry》2013,32(7):865-879
Abstract 1,2-O-Isopropylidene-α-D-xylo-hexofuranos-5-ulose (2) was deprotected in aqueous acid solution to give a mixture of at least six isomeric forms and one anhydro form of the parent ketoaldohexose, D-xylo-hexos-5-ulose (3), commonly referred to as 5-keto-glucose. Structural assignment of each form was made based on high field 1H and 13C NMR studies of the mixture in aqueous (D2O) solution. The dominant isomeric form of 3 was observed to have the pyranose structure 1R,5R-D-xlyo-hexo-pyranos-5-ulose (3a, 67 %) with the next most abundant form being an anhydro structure, 1S,5S-l,6-anhydro-D-xylo-hexopyranos-5-ulose (3c, 18 %). Included among the other isomers were the a and β-1,4-furanose (3d, 3e) and 1-aldehydrol β-5,2-furanose (3f) structures. The isomer present in least amount (3g, > 1 %) is assigned as the α-anomer of 3f. Experimentally determined JC-1,H-1 values were useful in support of assigned isomer structures. 相似文献