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.     

Assignment of juvabione diastereomers by 13C nuclear magnetic resonance spectroscopy

The determination of structures and partial assignments of stereochemistry of juvabione and some of its analogues can be made on the basis of ¹³C nuclear magnetic resonance studies. The complete ¹³C n.m.r. spectral assignments for juvabione and five analogues are reported.     

An Approach to NMR Assignment of Intrinsically Disordered Proteins

An efficient approach to NMR assignments in intrinsically disordered proteins is presented, making use of the good dispersion of cross peaks observed in [¹⁵N,¹³C′]‐ and [¹³C′,¹H^N]‐correlation spectra. The method involves the simultaneous collection of {3D (H)NCO(CAN)H and 3D (HACA)CON(CA)HA} spectra for backbone assignments via sequential H^N and H^α correlations and {3D (H)NCO(CACS)HS and 3D (HS)CS(CA)CO(N)H} spectra for side‐chain ¹H and ¹³C assignments, employing sequential ¹H data acquisitions with direct detection of both the amide and aliphatic protons. The efficacy of the approach for obtaining resonance assignments with complete backbone and side‐chain chemical shifts is demonstrated experimentally for the 61‐residue [¹³C,¹⁵N]‐labelled peptide of a voltage‐gated potassium channel protein of the Kv1.4 channel subunit. The general applicability of the approach for the characterisation of moderately sized globular proteins is also demonstrated.     

Carbon-13 NMR spectra of some labdane diterpenoids

Carbon-13 signal assignments of the labdane diterpenoids phlogantholide-A, its diacetate and isophlogantholide-A are reported. The assignments of the ¹³C NMR signals of 14-deoxyandrographolide and its diacetate, made earlier, have now been confirmed by lanthanide shift studies on the former and also by ¹³C spectral studies on anhydroandrographolide diacetate and 14-deoxy-11,12-didehydroandrographolide diacetate.     

19F, 13C NMR analysis of an oxygen carrier,perfluorotributylamine, and perfluoropentanoic acid

NMR relaxation measurement of perfluorocarbons (PFCs), such as perfluorotributylamine (FTBA), is a convenient method for the determination of oxygen concentrations in tissues and tumors. Previous relaxation studies of FTBA used different ¹⁹F NMR assignments causing some confusion. Fluorine‐detected ¹⁹F, ¹³C HMQC and HMBC and selectively ¹⁹F‐decoupled ¹³C NMR provided unequivocal ¹⁹F and ¹³C assignments for FTBA and perfluoropentanoic acid (FPA). Based on those assignments, ¹³C spin–lattice relaxation time constants (T₁) and effective correlation times for FTBA and FPA are reported and discussed. Copyright © 2003 John Wiley & Sons, Ltd.     

Application of the INEPT technique to 13C NMR assignments in polynuclear aromatic nitrogeneous heterocycles; 6H-pyrido[4,3-b]-5,11-dimethylcarbazole (ellipticine)

The ¹³C NMR spectrum of 6H-pyrido[4,3-b]-5,11-dimethylcarbazole has been re-examined to confirm the assignments using normal decoupled and coupled INEPT techniques. The results indicate that there were several errors in previous assignments. J(¹³C, ¹H) for the seven methine carbons have also been obtained.     

Total assignment of the 1H and 13C NMR spectra of pyrrolizino-[3,4,5-a,b]isoquinoline,benzo[1,2]pyrrolizino[3,4,5-a,b]isoquinoline and 2-methylthiopyrrolizino[3,4,5-a,b]isoquinoline

The total ¹H and ¹³C nmr spectral assignments of pyrrolizino[3,4,5-a,b]isoquinoline, benzo-[1,2]pyrrolizino[3,4,5-a,b]isoquinoline and 2-methylthiopyrrolizino[3,4,5-a,b]isoquinoline are reported. The concerted use of the COSY, HMQC, HMBC and nOe-difference experiments is used to generate total assignments of the ¹H and ¹³C nmr spectra.     

Isolation and characterization of a Tie2 kinase inhibitory sulfated triterpenoid from a green alga of the Tuemoya genus: complete assignment of the 1H and 13C spectra of a sulfated triterpenoid Tie2 kinase inhibitor

Bioassay‐guided fractionation of an extract of a Tuemoya sp., using an assay for inhibitors of the enzyme Tie2 kinase, afforded a mixture of the sulfated cycloartanol triterpenoids 1 and 2. We report the full ¹H and ¹³C NMR spectral assignments for 1 and the ¹³C NMR spectral assignments for 2. Copyright © 2003 John Wiley & Sons, Ltd.     

An investigation of the utility of using n.m.r. lanthanide shift reagents for 13C assignments in selected aromatic ethers and ketones. A detailed description of the lanthanide induced shift ratio method for lanthanide shift reagent–substrate geometry analysis

The ¹³C and ¹H spectra of a series of aromatic ketones, ethers and keto-ethers were studied using the lanthanide shift reagent (LSR) Yb(fod)₃ and the data analyzed using the lanthanide induced shift (LIS) ratio method. Studies were carried out on phenalenone, 6-methoxyphenalenone, 1- and 2-methoxynaphthalene, 1-indanone, 5- and 6-methoxy-1-indanone and flavone and the data obtained subjected to LSR-substrate geometry analysis as a means of making ¹³C assignments. The utility and limitations of the LSR method for making ¹³C assignments is discussed and the LIS ratio method for LSR-substrate geometry analysis is described in detail.     

Unequivocal total assignment of 13C and 1H NMR spectra of some pyrido[1,2‐a]pyrimidine derivatives by 2D‐NMR

We report the total assignments of the ¹³C and ¹H NMR spectra of some 4‐methyl‐2‐oxo‐(2H)‐pyrido[1,2‐a]pyrimidine and 2‐methyl‐4‐oxo‐(4H)‐pyrido[1,2‐a]pyrimidine derivatives. The products were characterized by ¹H and ¹³C NMR and reported data for similar compounds. No comparative data for the two sets of isomeric compounds with respect to ¹³C and ¹H NMR have been reported to date. We made some detailed studies of the 2D NMR spectra of these compounds and observed that assignments made for non‐protonated carbon atoms by us and those reported in the literature for similar compounds need correction. The revised assignments were made on the basis of heteronuclear single quantum correlation (HSQC) and heteronuclear multiple bond correlation (HMBC) techniques. Copyright © 2003 John Wiley & Sons, Ltd.     

Complete assignments of the 1H and 13C NMR spectra of 15 limonoids

Unambiguous and complete assignments of ¹H and ¹³C NMR chemical shifts for 15 limonoids, eight of them found in natural sources and seven other synthetic derivatives, are presented. The assignments are based on 2D shift‐correlated [¹H,¹H‐COSY, ¹H,¹³C‐gHSQC‐¹J(C,H), ¹H,¹³C‐gHMBC‐ⁿJ(C,H) (n = 2 and 3)] and NOE experiments. Copyright © 2003 John Wiley & Sons, Ltd.     

Structural characterization of hypoglycin B,a diastereomeric dipeptide from the ackee fruit (Blighia sapida Koenig) by NMR experiments

The dipeptide hypoglycin B, one of two toxins of the ackee fruit (Blighia sapida Koenig), was characterized for the first time by NMR spectral data, which led to the discovery that it exists naturally as a pair of diastereomers. No distinction was observed in the ¹H NMR signals of the diastereomers; however, complete and distinct ¹³C NMR assignments for the individual diastereomers were made. The ¹³C NMR spectrum of hypoglycin B compared very well with that of the corresponding signals in the spectrum for hypoglycin A, which is one of its constituent amino acids. The ¹H and ¹³C NMR assignments were further supported by DEPT, gCOSY, gHSQC and gHMBC experiments. Copyright © 2009 John Wiley & Sons, Ltd.     

Two-dimensional1H and13C NMR spectroscopy and the structural aspects of amylose and amylopectin

Summary A complete assignment of the¹³C and¹H NMR signals of amylose dissolved in dimethylsulfoxide was achieved using two-dimensional H-H and C-H correlated spectroscopy and deuterium exchange. The same methods together with an INEPT experiment provided the assignments of the¹H and¹³C NMR signals of the amylose type glucan units, the branch end glucan fragments, and a few assignments of nuclei within the branching glucan units of amylopectin dissolved in dimethylsulfoxide. From these assignments and from the integration of pertinent proton signals the branching degrees of amylose and amylopectin were derived to amount to 3.9 and 8–9%.

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Zweidimensionale¹H und¹³C-NMR-Spektroskopie und die strukturellen Aspekte von Amylose und Amylopektin

Zusammenfassung Die vollständige Zuordnung der¹³C- und¹H-NMR-Signale von in Dimethylsulfoxid gelöster Amylose konnte mit Hilfe zweidimensionaler H-H- und C-H-Korrelationsspektroskopie und Deuteriumaustausch erzielt werden. Die gleichen Methoden sowie ein INEPT-Experiment ermöglichten auch die Zuordnung der¹³C- und¹H-NMR-Signale der amylosischen Glucaneinheiten, der Verzweigungsendfragmente und einzelner Kerne im Bereich der Verzweigungsstellen von in Dimethylsulfoxid gelöstem Amylopektin. Aus diesen Zuordnungen und der Integration entsprechender Protonensignale konnte ein Verzweigungsgrad von Amylose und Amylopektin von 3.9 und 8–9% abgeleitet werden.

     

The 13C NMR spectra of tallysomycin and its zinc(II) complex

Using the carbon assignments of bleomycin A₂ as well as those of a series of model compounds, the ¹³C NMR assignments of the antitumor antibiotic tallysomycin (TLM) have been made. With the aid of the carbon assignments the metal binding properties of the new antibiotic toward Zn(II) have been investigated.     

13C chemical shifts of symmetrically substituted biphenyls: Unambiguous signal assignment for the carbons ortho and para to an aryl group

The natural abundance ¹³C NMR spectra of 2,2′-dimethyl-, 2,2′-dimethoxy- and 2,2′-dihydroxybiphenyls, and a series of 2,2′-dimethoxy-5,5′-disubstituted biphenyls were recorded. Unambiguous signal assignments of the carbons ortho and para to an aryl ring in biphenyls were made by selective deuteration and/or the graphical method for ¹H single frequency off-resonance decoupled spectra. Contrary to the reported assignments, it was shown that the signal for C-6 in 2,2′-dimethylbiphenyl clearly appears at lower field than that for C-4. The signals for the ortho carbons (C-6) of 2,2′-dimethoxy-5,5′-disubstituted biphenyls generally appeared at lower fields than those for the para carbons (C-4). The validity of applying deuterium isotope shifts to the assignments of ¹³C chemical shifts of di- and tetra-substituted biphenyls is also discussed.     

Deuterium-induced 13C nuclear magnetic resonance isotope shifts and 13C?2H couplings for signal assignments and determination of deuteration site in cyclooctanone

Unambiguous signal assignments in the ¹³C spectra of monodeuterated cyclooctanones derived from the lead tetraacetate or silver oxide/bromine oxidations of the corresponding 1-monodeutero-alcohols have been obtained from deuterium-induced ¹³C isotope shifts and geminal and vicinal ¹³C? ²H spin-spin coupling constants. The label in the ketones is shown to be in position 5.     

Carbon-13 nuclear magnetic resonance spectra of exo- and endo-2-norbornyltrimethyl-stannanes: Corrected assignments

The ¹³C NMR spectra of pure exo-2-norbornyltrimethylstannane and a mixture of the exo- and endo-isomers have been recorded. ¹H–¹³C polarization transfer spectra have been obtained and require the previously reported assignments for C-3 and C-4 in the exo-isomer to be reversed. The reported assignments for the endo-isomer are correct. The new assignment for C-4-exo [with J(¹¹⁹Sn,¹³C) vic=12 Hz, instead of the previously assigned J(vic)=23 Hz], has a very minor effect on the nature of the Karplus curve [for ³J(¹¹⁹Sn,¹³C)] generated previously.     

13C- and 1H-NMR. Assignments for colchicine derivatives

The ¹³C-NMR. spectra of a number of colchicine derivatives are given comprising examples of the normal series ( 4→10 ), iso series ( 11→16 ) and colchicine series ( 17 ), which were either reported in the literature or obtained by partial synthesis or degradation reactions. The ¹³C-NMR. assignments were made by comparisons with known compounds and selective single-frequency offresonance decoupling experiments. Selective proton decoupling experiments have also allowed assignments of the H —C(11) and H —C(12) protons of the iso and colchicine series.     

Complete assignment of the 1H and 13C NMR Spectra of 11,12-Dimethoxy[1]benzothieno[3,2-a]-4,7-phenanthroline and its 8-Chloro Analogue: Concerted Use of Two-Dimensional NMR Techniques

The ¹H and ¹³C nmr spectra of 11,12-dimethoxy[1]benzothieno[3,2-a]-4,7-phenanthroline and its 8-chloro precursor were totally assigned using a combination of two-dimensional nmr techniques. After correlation of the majority of the proton signals by a COSY spectrum and one-bond heteronuclear correlation, the full assignment of the ¹H and ¹³C nmr spectra of the novel heterocyclic compounds required the application of long-range CH coupling information particularly for quaternary carbon resonance assignments and the orientations of individual spin systems relative to one another. Key long-range heteronuclear couplings in both compounds served to confirm the one-bond heteronuclear correlations. Unequivocal interpretation of the spectral data leads to the complete assignments of the resonances.     

Carbon-13 NMR spectroscopy of hop bitter substances

The ¹³C NMR spectra of the most important hop bitter substances are analysed. All individual carbon atoms are assigned, except the oxygen bonded sp² carbon atoms. Most assignments are made partly by comparison with analogous compounds and partly by reference to literature data. Cross-correlations with the ¹H NMR shifts are made for two main products and confirm the correctness of the assignments. All data are in agreement with the known structures.