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1.
4-13C-isoprene was prepared by the Wittig reaction. All reaction steps were optimised using unlabelled compounds. By reaction with triphenyl phosphine, 13C labelled methyl iodide afforded labelled methyl-triphenyl phosphine iodide in 84% yield. This reacted with meth acrolein with production of 4-13C-isoprene in 64% yield. Labelled polyisoprene was prepared by anionic polymerisation initiated by t-butyl lithium. Based on 13CH3I the overall yield is ca 30%. The polymer was characterized by 1H and 13C NMR spectroscopy. The contribution of each microstructure was [cis 1-4, 72%]; [trans 1-4, 10%]; [3-4, 18%].  相似文献   

2.
8-Trifluoromethyl-6,7-dihydro-5H-1,4,8a-triaza-s-indacene and 9-trifluoromethyl-5,6,7,8-tetrahydropyrazolo[5,1-b]quinazolines were efficiently generated by condensation of 5(3)-aminopyrazoles with (2-ethoxycycloalkenyl)-2,2,2-trifluoroethanones and isolated in excellent yields. The regiochemistry of the prepared compounds was established by 1H, 13C and 19F NMR spectroscopy and X-ray diffraction analysis.  相似文献   

3.
A new synthetic route for the quorum sensing signal Autoinducer-2 (AI-2) is described and used for the preparation of [4-13C]-AI-2 starting from [1-13C]-bromoacetic acid. The key step in this process was the enantioselective reduction of an intermediate ketone. This synthesis provides, selectively, both enantiomers of the labelled or unlabelled parent compound, (R) or (S)-4,5-dihydroxypentane-2,3-dione (DPD) and was used for an improved synthesis of [1-13C]-AI-2.  相似文献   

4.
Based on analysis of 1H and 13C NMR spectra of 9H-pyrimido[4,5-b]indole and its 4-phenyl-2-substituted derivatives, we have made assignments for the signals from the 1H and 13C atoms of these compounds.  相似文献   

5.
Aspergiolide A, a novel antitumor compound, was produced by a marine-derived filamentous fungus Aspergillus glaucus. The biosynthesis of it was unambiguously determined by feeding experiments using [l-13C]sodium acetate, [2-13C]sodium acetate, and [1,2-13C2]sodium acetate precursors followed by 13C NMR spectroscopic investigation of the isolated products. Analysis of the patterns of 13C-enrichment revealed that all 25 carbon atoms in skeleton of aspergiolide A were derived from labeled acetate. And among them, 12 carbon atoms were labeled from the carboxylic group of acetate, while the other 13 carbon atoms were labeled from the methylic group of acetate. Besides, the labeling pattern of [1,2-13C2]sodium acetate feeding experiment demonstrated that 12 intact acetate units were incorporated in aspergiolide A by polyketide pathway.  相似文献   

6.
A straightforward, two-step synthesis of fluoro substituted chromeno[2,3-c]pyrazol- and [1]benzothieno[2′,3′:5,6]pyrano[2,3-c]pyrazol-4(1H)-ones, respectively, is presented. Hence, treatment of 1-substituted or 1,3-disubstituted 2-pyrazolin-5-ones with fluoro substituted 2-fluorobenzoyl chlorides or 3-chloro-6-fluoro-1-benzothiophene-2-carbonyl chloride using calcium hydroxide in refluxing 1,4-dioxane gave the corresponding 4-aroylpyrazol-5-ols, which were cyclized into the fused ring systems. 5-Fluorochromeno[2,3-c]pyrazol-4(1H)-one was obtained upon treatment of the 1-(4-methoxybenzyl) protected congener with trifluoroacetic acid. Treatment of 5-fluorochromeno[2,3-c]pyrazol-4(1H)-ones with methylhydrazine afforded novel tetracyclic ring systems such as 2-methyl-7-phenyl-2,7-dihydropyrazolo[4′,3′:5,6]pyrano[4,3,2-cd]indazole. Detailed NMR spectroscopic investigations (1H, 13C, 15N, 19F) with the obtained compounds were undertaken.  相似文献   

7.
A simple and efficient synthetic route to the novel 3a,4-dihydro-3H,7H- and 4H,7H-pyrazolo[4′,3′:5,6]pyrano[4,3-c][1,2]oxazole ring systems from 3-(prop-2-en-1-yloxy)- or 3-(prop-2-yn-1-yloxy)-1H-pyrazole-4-carbaldehyde oximes has been developed by employing the intramolecular nitrile oxide cycloaddition (INOC) reaction as the key step. The configuration of intermediate aldoximes was unambiguously determined using NOESY experimental data and comparison of the magnitudes of 1JCH coupling constants of the iminyl moiety, which were greater by approximately 13 Hz for the predominant syn isomer. The structures of the obtained heterocyclic products were confirmed by detailed 1H, 13C and 15N NMR spectroscopic experiments and HRMS measurements.  相似文献   

8.
Isotope ratio mass spectrometry (IRMS) is applied to confirm testosterone (T) abuse by determining the carbon isotope ratios (δ13C value). However, 13C labeled standards can be used to control the δ13C value and produce manipulated T which cannot be detected by the current method. A method was explored to remove the 13C labeled atom at C-3 from the molecule of androsterone (Andro), the metabolite of T in urine, to produce the resultant (A-nor-5α-androstane-2,17-dione, ANAD). The difference in δ13C values between Andro and ANAD (Δδ13CAndro–ANAD, ‰) would change significantly in case manipulated T is abused. Twenty-one volunteers administered T manipulated with different 13C labeled standards. The collected urine samples were analyzed with the established method, and the maximum value of Δδ13CAndro–ANAD post ingestion ranged from 3.0‰ to 8.8‰. Based on the population reference, the cut-off value of Δδ13CAndro–ANAD for positive result was suggested as 1.2‰. The developed method could be used to detect T manipulated with 3-13C labeled standards.  相似文献   

9.
Quantitative analysis of specifically deuterated compounds can be achieved by a number of conventional methods, such as mass spectroscopy, or by quantifying the residual 1H NMR signals compared to signals from internal standards. However, site specific quantification using these methods becomes challenging when dealing with non-specifically or randomly deuterated compounds that are produced by metal catalyzed hydrothermal reactions in D2O, one of the most convenient deuteration methods. In this study, deuterium-induced NMR isotope shifts of quaternary 13C resonances neighboring deuterated sites have been utilized to quantify the degree of isotope labeling of molecular sites in non-specifically deuterated molecules. By probing 13C NMR signals while decoupling both proton and deuterium nuclei, it is possible to resolve 13C resonances of the different isotopologues based on the isotopic shifts and the degree of deuteration of the carbon atoms. We demonstrate that in different isotopologues, the same quaternary carbon, neighboring partially deuterated carbon atoms, are affected to an equal extent by relaxation. Decoupling both nuclei (1H, 2H) resolves closely separated quaternary 13C signals of the different isotopologues, and allows their accurate integration and quantification under short relaxation delays (D1 = 1 s) and hence fast accumulative spectral acquisition. We have performed a number of approaches to quantify the deuterium content at different specific sites to demonstrate a convenient and generic analysis method for use in randomly deuterated molecules, or in cases of specifically deuterated molecules where back-exchange processes may take place during work up.  相似文献   

10.
S. Guillou  F. Terrier 《Tetrahedron》2009,65(43):8891-190
In the course of our program focused on the preparation of high-nitrogen content heterocyclic compounds, we wish to report an original synthesis of the tricyclic 7-azidofurazano[3,4-b]tetrazolopyrazine via an unprecedented reaction between 2,6-dimethoxy-3,5-dinitropyrazine and hydrazine hydrate. This compound was identified by an X-ray diffraction analysis. Further studies of its structure by 15N and 13C NMR spectroscopy were carried out in different solvents. This allowed us to observe a noteworthy equilibrium involving three forms resulting from the reversible opening of a tetrazole ring.  相似文献   

11.
The 1H, 13C correlation NMR spectroscopy utilizes JCH couplings in molecules, and provides important structural information from small organic molecules in the form of carbon chemical shifts and carbon-proton connectivities. The full potential of the 1H, 13C correlation NMR spectroscopy has not been realized in the Chemical Weapons Convention (CWC) related verification analyses due to the sample matrix, which usually contains a high amount of non-related compounds obscuring the correlations of the relevant compounds. Here, the results of the application of 1H, 13C, 31P triple-resonance NMR spectroscopy in characterization of OP compounds related to the CWC are presented. With a set of two-dimensional triple-resonance experiments the JHP, JCH and JPC couplings are utilized to map the connectivities of the atoms in OP compounds and to extract the carbon chemical shift information. With the use of the proposed pulse sequences the correlations from the OP compounds can be recorded without significant artifacts from the non-OP compound impurities in the sample. Further selectivity of the observed correlations is achieved with the application of phosphorus band-selective pulse in the pulse sequences to assist the analysis of multiple OP compounds in mixture samples. The use of the triple-resonance experiments in the analysis of a complex sample is shown with a test mixture containing typical scheduled OP compounds, including the characteristic degradation products of nerve agents sarin, soman, and VX. The viability of the approach in verification analysis is demonstrated in the analysis of the 30th OPCW Proficiency Test sample.  相似文献   

12.
Biosynthetic studies on naphthylisoquinoline alkaloids involving a specifically [1,1′-13C2]-labeled dihydroisoquinoline 7 are described. The synthesized precursor 7 was fed to callus cultures of Triphyophyllum peltatum and the isolated secondary metabolites were characterized by spectroscopic methods (1H, 13C NMR, and INADEQUATE experiments). The unambiguous incorporation of the precursor into dioncophylline A and two minor naphthylisoquinolines, together with the formation of the labeled corresponding trans-configured tetrahydroisoquinoline, proves the implication of such advanced intermediates in the proposed biosynthetic pathway of naphthylisoquinoline alkaloids.  相似文献   

13.
Ketenylidenetriphenylphosphorane, Ph3PCCO (2), reacts selectively with the ω-hydroxy group of the alkene-carbene complexes (OC)4CrC(η2-NMeCH2CHCHCH2OH)R1 (1) (R1=Me: (1a); Ph: (1b)) to give the acyl ylide terminated complexes (OC)4CrC[(4,5-η2)-NMeCH2CHCHCH2O(O)C-CHPPh3]R1 (3) (R1=Me: (3a); Ph: (3b)). Complexes 3 undergo Wittig alkenation reactions with aldehydes such as 2-alkynals, R2-CC-CHO (R2=H, SiMe3, Ph), to give the corresponding 4Z, 9E-dien-11-ynes (OC)4CrC[(4,5-η2)-NMeCH2CHCHCH2O(O)C-CHCH-CC-R2]R1 (4-6) (R1=Me, R2=H, SiMe3, Ph: (4a-6a); R1=Ph, R2=H, SiMe3, Ph: (4b-6b)). All complexes were characterized in solution by one- and two-dimensional NMR spectroscopy (1H, 13C, 29Si, 31P, 1H/1H COSY, 13C/1H HETCOR, 31P/31P EXSY).  相似文献   

14.
Simulation of 2D 1H homo- and 1H-13C heteronuclear NMR spectra of organic molecules are here suggested as a tool in the structure elucidation of organic compounds. DFT calculations of 1H and 13C chemical shifts are performed on a sample compound, the ethyl ester of the exo-2-norbornanecarbamic acid, with the mPW1PW91 method using the 6-31G(d) basis set, following a full optimization of the geometry. Homo and heteronuclear spin-spin coupling constants are also calculated, providing full prediction of the common 2D 1H-1H COSY, 2D 1H-13C HSQC, and 2D 1H-13C HMBC.  相似文献   

15.
The condensation in one step of a series of salicylaldehydes and 2-amino-5-nitrophenol with 1-naphthylboronic acid, 2-naphthylboronic acid, and o-tolylboronic acid to give the corresponding boronates 1a-3a, 1b-3b and 1c-3d, is reported. The X-ray crystal structures of 1a, 2b and 3b allowed determining the α- and β-angle between the stilbene skeleton and the aryl or naphthylboronic fragments; these values are indicative of different conformations for the aryl moieties around the (B-C) boron-carbon bond which could potentially modulate the electronic properties on the boron stilbene compounds. All compounds were characterized by 1H, 11B and 13C NMR spectroscopy, UV, IR and mass spectrometry. Second- and third-order non-linear optical characterizations were also performed by EFISH and THG Maker Fringe techniques, respectively. Compounds 3a-3d containing an -N(Et)2 donor group gave the best NLO response in second- and third-order.  相似文献   

16.
The stereochemistry of syn and anti-forms of bridged bicyclo[3.n.1]-2-ene, tricyclo[7.n.1.0]-2-ene (n=1-3) and bicyclo[4.3.1]dec-7-ene derivatives can be assigned from the 13C chemical shift difference of the double bond. Both syn-9-R-bicyclo[3.3.1]non-2-enes and syn-13-R-tricyclo[7.3.1.02,7]tridec-2(7)-enes have a large shielding difference between sp2 carbons, while the corresponding anti-forms have a smaller one. In contrast, 8-R-bicyclo[3.2.1]oct-2-enes and 12-R-tricyclo[7.2.1.02,7]dodec-2(7)-enes have an inverse correlation. The reason of this specificity is the influence of the γ-gauche effect on the chemical shift of C(2) atom. The GIAO theory has been applied to investigate the 13C chemical shifts. The conformational equilibrium in the formamide group of 13-formylamino-tricyclo[7.3.1.02,7]tridec-2(7)-enes has been studied.  相似文献   

17.
The labelling and coupling patterns of secobotrytrienediol, biosynthesised from [1-13C] and [1,2-13C2]-acetate by the fungus Botrytis cinerea, have been used to define the mode of formation and the biogenetic origin of secobotrytrienediol. [10-2H]-Botrydiol was not incorporated into the secobotryane skeleton. In addition, this feeding experiment led to the isolation of three new unlabelled derivatives possessing a secobotryane skeleton, secobotrydiene-3,10,15-triol, secobotrydiene-3,4,10,15-tetraol, and secobotrytriene-10,12,15-triol.  相似文献   

18.
The halocarbonyls BrM(CO)5, M = Mn and Re, were reacted with the KN(SePPh2)2 salt in equimolar amounts; the reactions were thermally carried out and resulted in the generation of the hexacoordinated isostructural complexes [M(CO)4{Ph2P(Se)NP(Se)Ph2-Se,Se′}] with a twist MSePNPSe ring conformation. Complexes’ characterizations were achieved by IR, mass, NMR (1H, 13C, 31P, 77Se) spectroscopies, and by single-crystal X-ray diffraction.  相似文献   

19.
[6Li]-α-(phenylthio)benzyllithium 1-6Li was studied in THF/[D8]THF solution (1:1) in the presence of several acyclic and cyclic polyether ligands by 1H,6Li-HOESY, 1H and 13C NMR spectroscopy. The question whether these ligands are bonded to lithium or not is important for physical–organic investigations as well as for studies of the ground state of (stereoselective) reactions of organolithium compounds in the presence of such ligands. Dimethoxyethane is not bonded to lithium under these conditions. The acyclic ethers diglyme and triglyme coordinate only weakly to the organolithium compound and form contact ion pairs (CIPs) at 25°C. At −80°C, CIPs are in equilibrium with separated ion pairs (SIPs). Very stable complexes of 1-6Li are obtained with crown ether ligands. Addition of 12-crown-4 and 15-crown-5, respectively, results in the exclusive formation of SIPs at 25°C and −80°C. With 18-crown-6, a CIP–SIP equilibrium is observed at 25°C which is shifted entirely to the SIP side at −80°C. Graphical analyses of the 1H and 13C NMR spectra of the polyether complexes of 1-6Li revealed correlations between the chemical shifts of the para phenyl carbon C-5, the para phenyl proton H-5, the benzylic carbon C-1, and the proton–carbon coupling constant J(C-1,H-1) of 1-Li, which are useful probes for the charge distribution within the carbanionic moiety of 1-6Li in the respective complexes, and thus for the ion pair character as a function of the polyether complexation of lithium.  相似文献   

20.
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