13C NMR assignments

In 2006, Milosavljevic and co-workers64 reported a study of the complete 4H and 13C NMR assignment of a new triterpenoid saponin, leucantho-side-A (13), from Cephalaria leucantha L. In the course of determining the structure and assigning the spectra, the authors made extensive use of the normal ensemble of 2D NMR experiments in use for the characterization of natural product structures HSQC, HMBC, DQF-COSY, TOCSY, and NOESY. The authors supplemented the aforementioned list of experiments with 2D /-resolved, DINE-(Double INEPT-Edited)-HSQC, and INADEQUATE spectra. The authors made no mention of the use of the connectivity information derived from the 1,1-ADEQUATE spectrum in the assembly of the triterpene nucleus of the molecule but reported extensive tabulations of the 1,1-ADEQUATE correlations that were used to sequence and assign the saccharide resonances of the tri- and di-saccharide sub-units, 14 and 15, respectively, linked to the triterpene nucleus. 

On the basis of their 13C NMR assignments (see below), 111—111 correlation spectroscopy (COSY) and H-13C COSY experiments allowed to assign the H NMR data of a series of sparteine analogues and derivatives (compounds 24-27). These data are collected in Table 2 <2003JST275>. Detailed 111 NMR assignments for other sparteine derivatives are also available in the literature (see, for instance, <2005JST75>). 

Table 3 13C-NMR assignments of some sparteine-related compounds...

Valproic Acid and Sodium Valproate Comprehensive Profile Table 4. 13C NMR assignments for sodium valproate... 

Also, 13C NMR assignments have been published for a recently synthesized phosphorus-containing ring system imidazo[l,2-r-][l,3,2]oxazaphosphinine 49 <1996TL977>. The chemical shifts as well as the /C P coupling constants are shown in Table 2. 

Rochet and Lancelin50 reported revised 1H and 13C NMR assignments of the polyene antibiotic Filipin m (83). This macrolide which was isolated from Streptomyces filipinensis was reinvestigated in DMSO-dg solution using homonuclear and heteronuclear correlation spectroscopy. In addition to several corrections to previous 1H NMR... 

Swinny, E.E., Bloor, S.J., and Wong, H. 2000. H and 13C NMR assignments for the 3-deoxyan-thocyanins, luteolinidin-5-glucoside and apigen-inidin-5-glucoside. Magn. Reson. Chem. 38 1031-1033. 

Crystal structure data are available for an indole—trinitrobenzene complex (2) and for the lithium and sodium salts in the presence of polyamine ligands (3). The crystal structure of indole itself is evidently disordered (4). Table 1 gives the and C-nmr assignments in CDC13 (5). 13C-nmr assignments have been tabulated for many other indole derivatives (6). 

Kaiser CR, Pitombo LF, Pinto AC (2001) Complete 1H and 13C NMR Assignments of Chamigrenes from Aplysia dactilomela. Mag Reson Chem 39 147... 

Partial 13C NMR assignments on colchicine are shown in [137]. (102) The benzylic methylene carbon nuclei in the 13C NMR spectrum of emetine [138] absorb (<5 29-1) at much higher frequency than in related carbolines (see ochrolifuanine—Section XII.K). (103)... 

The combination of lanthanide shift reagents and 2D NMR techniques (COSY and NOESY) was applied to the H- and 13C-NMR assignments of ethylene-vinyl acetate... 

The work realized by Dauson et al [127] is of particular interest for the H NMR and 13C NMR assignments of these type of molecules. The isomers a-lapachone and P-lapachone can be easily distinguished, attending to the pattern that present the linear and angular pyranonaphthoquinones in their NMR spectra. In the H NMR spectra, the signals corresponding to the aromatic protons appear in two different forms. In the case of a-cycled compounds, the aromatic protons have a symmetric environment and the hydrogens H5 and Hg are equivalent as... 

NOESY NMR spectra were used to characterise the lanthanide complexes Ln(L)3+, where L = tris[(2-pyridyl)methyl]amine or tris[6- (2-7V,7V-diet-hylcarbamoyl)pyridyl methyl]ketone, Ln = La Lu except Pm.1236 The H NMR spectra of Ln(L)Cl3, where L = N403 tripodal ligands, Ln = La - Lu, except Pm, show effective C3v symmetry in solution.1237 H and 13C NMR assignments, based on COSY, NOESY and HMQC data, have beeen made for [LnL]Cl3. H20, where Ln = La, Ce, Eu L = chiral macrocycle derived from (1 R,2R)-1,2-diphenylethylenediamine and 2,6-diformylpyridine.1238... 

The assignments shown in Fig. 17B are made based on the connectivities shown above and on consideration of the magnetic equivalency of the methylene protons. The H NMR assignments have been extended to 13C NMR assignment using the l3C- H heteronuclear shift-correlated 2D NMR technique (13C- H COSY).199... 

Lauraceae), was assigned the structure 26 based on spectroscopic evidence (38). The oxygenation pattern of the aromatic rings and the presence of a C-2 phenolic function were determined by its UV spectrum, coupled with base-induced bathochromic shifts. The location of the hydroxy function at C-4, its stereochemical disposition, and the stereochemistry of 6a-H were determined with the help of and 13C NMR data and comparison with those of known compounds. The 3H and 13C NMR assignments for srilankine (26) are depicted in Fig. 1. 

A limited number of persistent carbocations from fluoranthene PAHs have been generated.39 Available NMR data are collected in Fig. 53. The site of attack is the same for parent fluoranthene and benzo[b]fluoranthene. Methoxy substitution directs the attack ortho to the substituent. The resulting non-alternant carbocations are paratropic, and most proton resonances are shielded relative to their neutral precursors. The 13C NMR assignments and the derived A<5 values are gathered. The uniform charge alternation pattern in the carbocations derived from fluoranthene and benzo[b] fluoranthene breaks down at C-7b. The methoxy derivative exhibits limited charge delocalization. 

H-NMR spectra of compound 25 estimated its molecular formula as C16H12O4. The H- and 13C-NMR assignments were compared with those of the literature and all chemical shifts and coupling patterns were found to be identical with those of formononetin [92,95]. Thus the 25 was confirmed as formononetin (7-hydoxy-4 -methoxyisoflavone, 25). The compound 25 was acetylated and the bioactivity of acetylated formononetin (26) was also evaluated. 

Another enzyme cofactor, flavine adenine dinucleotide (FAD) disodium salt, has been studied by 13C nmr. Assignments of the resonances have been made by comparing the spectrum of FAD with its constituents, adenosine 5 -diphosphate trisodium salt and riboflavin -monophosphate sodium salt (Breitmaier and Voelter, 1972). 

Satake, M., S. Ishida, and T.J. Yasumoto, Structural confirmation of maitotoxin based on complete 13C NMR assignments and the three-dimensional PFG NOESY-HMQC spectrum. JAm Chem Soc, 1975 117 7019. 

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