Structure Elucidation by Modern NMR

Structure and stereochemistry of novel ecdysteroids from the roots of Serratula wolffii

“…The structures of products were determined by means of MS, CD in addition with comprehensive one-and two-dimensional NMR methods ( 1 H, 1 H-COSY, NOESY (mixing time = 400 ms), HMQC, HMQC-TOCSY (mixing time = 80 ms) and HMBC), using widely accepted strategies. [3,4] Chemical shifts are given on the δ-scale and were referenced to the solvent (MeOH-d 4 : δ C = 49.15 and δ H = 3.31). In the one-dimensional measurements ( 1 H, 13 C and DEPT-135), 64 K data points were used for the FID, sweep widths: 8000 and 30 000 Hz, respectively.…”

Ecdysteroid-containing food supplements from Cyanotis arachnoidea on the European market: evidence for spinach product counterfeiting

“…Most 1 H assignments were accomplished using general knowledge of chemical shift dispersion with the aid of the proton-proton coupling pattern ( 1 H NMR spectra). The NMR signals of the products were assigned by comprehensive one- and two-dimensional NMR methods using widely accepted strategies1516.…”

Synthesis and properties of methyl hydropyrimidineacetates

“…The second direction of the reaction is that the nucleophile diamine attacks the 4-CO group of the heterocycle with subsequent opening of the heterocycle to form the benzimidazole fragment (compounds 6c,d) with subsequent hydrolysis of the amide to give compounds with the structures 5a,b,e. The structures of the compounds synthesized were confirmed by IR, mass spectrometry, and 1 H and 13 C NMR spectroscopy ( Table 2) with assignment of the signals on the basis of general rules of additivity of substituents and published spectral data of model compounds [5][6][7][8][9].…”

“…The substituent R in all the compounds synthesized has the form of a benzene ring with varying degrees of substitution. The spectral lines of the carbon atoms of the benzene ring for compounds 2a-e and 4a-e in their 13 H NMR spectra were identified on the basis of the refined in the given word increments (C i = 12.05, C o = -1.32, C m = 2.06, and C p = -0.54 ppm) of the influence of the substituent in the pyrimidine ring [8], in the case of compounds 5a,b,e the refined influence of the fragment NHCH 2 CH 2 [5][6][7] (C i = 19.97, C o = -16.41, C m = 0.43, and C p = -12.69 ppm), but in compounds 6c-d by comparison with related fragments in model compounds [9]. The character of the substitution on the benzene ring has an important effect on the structural characteristics and properties of the compound.…”

“…With the necessity to assign spectral lines we used the APT 13 C NMR method [5,6]. The investigation compounds are divided to for classes according the characteristic features of their structural fragments.…”