SelEXSIDE: Fast and Easy Measurement of Multiple-Bond <sup>1</sup>H,<sup>13</sup>C Coupling Constants for Stereochemical Analysis

Heise, Bert; Tatolo, Godiraone

doi:10.1021/ol301078q

Cited by 20 publications

(33 citation statements)

References 19 publications

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“…Quite obvious, the unique zero‐crossing point at Δ = 1/ 2 J C12H11a occurs for Δ ~0.45 s, which corresponds to a long‐range coupling constant 2 J C12H11a of ~2.2 Hz, consistent with only one previously reported experimental value . The other experimentally determined coupling constant values and the calculated value are much smaller . For verification, a series of spectra were simulated for this extended spin system (Figure ) using the following coupling constants: 2 J C12H11a = 2.2 Hz, 2 J H11aH11b = 17.5 Hz, and 3 J H11aH12 = 8.4 Hz, the latter extracted from the 1D 1 H proton spectrum.…”

Section: Resultsmentioning

confidence: 97%

“…In the 1 H NMR spectrum of strychnine (Figure 3 In Figure 4, 1D 13 C-selective HMBC spectra showing the resonance of H11a (δ = 3.08 ppm) for which the reported 2 J C12H11a coupling constant ranges from 0.8 to 2.5 Hz [29,31,45,52,53] (calculated −0.8 Hz) are presented. The reliable determination of this 2 J CH coupling constant in a CHH′H″ spin system is most challenging, because of its small magnitude, and because of the complicated multiplet pattern, a severe problem for methods relying on fitting procedures for extracting n J CH values.…”

Section: Experimental Evidencementioning

confidence: 99%

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Measurement of long‐range heteronuclear coupling constants using the peak intensity in classical 1D HMBC spectra

Bigler

Furrer

2018

Magnetic Reson in Chemistry

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In this contribution, we show that the magnitude of heteronuclear long-range coupling constants can be directly extracted from the classical 1D HMBC spectra, as all multiplet lines of a cross-peak always and exclusively vanish for the condition Δ = k/ J . To the best of our knowledge, this feature of the classical HMBC has not yet been noticed and exploited. This condition holds true, irrespective of the magnitude and numbers of additional active and passive homonuclear J couplings. Alternatively, the J value may also be evaluated by fitting the peak's intensity in the individual spectra to its simple sin(π J Δ)exp(-Δ/T ) dependence. Compared to the previously proposed J-HMBC sequences that also use the variation of the cross-peak's intensity for extracting the coupling constants, the classical HMBC pulse sequence is significantly more sensitive.

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Section: Resultsmentioning

confidence: 97%

Section: Experimental Evidencementioning

confidence: 99%

Measurement of long‐range heteronuclear coupling constants using the peak intensity in classical 1D HMBC spectra

Bigler

Furrer

2018

Magnetic Reson in Chemistry

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“…Recently, the usage of a proton and carbon selective version (Selexside) was published. [12] Thus, the following values were obtained for 4a: H-6 couples with C-4 (4.1 Hz), C-7 (3.2 Hz), C-9 (ca. 1 Hz) and C-9a (7.2 Hz); H-7 couples with C-6 (6.3 Hz), C-8 (<2 Hz), C-9 (7.9 Hz) and C-9a (<2 Hz); and H-8 couples with C-6 (9.4 Hz), C-7 (<2 Hz), C-9 (0.9 Hz) and C-9a (9.1 Hz).…”

Section: Nmr Datamentioning

confidence: 84%

¹H, ¹³C and ¹⁵N NMR spectral analysis of substituted 1,2,3,4‐tetrahydro‐pyrido[1,2‐a]pyrimidines

Girreser

Bluhm

Clement

et al. 2013

Magnetic Reson in Chemistry

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The NMR spectroscopic data of a series of thirty-four 3-acylpyrido[1,2-a]pyrimidinium salts are analyzed, which were prepared as either perchlorates or chlorides. Methyl group substituted 3-aroyltetrahydropyrido[1,2-a]pyrimidines with the methyl substituent in positions 6, 8 and 9 as well as both in positions 6 and 8 were investigated bearing various aroyl substituents. Unequivocal assignment of all resonances was achieved via two-dimensional (1)H,(1)H-COSY measurements, (1)H,(13)C and (1)H,(15)N HSQC as well as HMBC experiments, and important diagnostic CH and NH couplings in the heteroaromatic ring system are evaluated. The influence of the methyl substituents was analyzed on the proton, carbon and nitrogen shifts. A significant effect of the counter ion on some chemical shifts of the nuclei under discussion of the pyridopyrimidines is found, allowing the indirect detection of the anion, which is confirmed by direct measurement of the (35)Cl nucleus of the perchlorates.

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“…Hadamard encoding is achieved by the IMPRESS technique described by Krishnamurthy, 14 replacing SelEXSIDEs selective 13 C inversion pulses with a series of n symmetrically shied laminar pulses 15 which are phase-encoded to match Hadamard matrices, H n .…”

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confidence: 99%

“…The desired sub-spectra for each 13 13 Fig. 2 illustrates the systematic increase in signal-tonoise ratio obtained with ImpEXSIDE (green) compared to the parent SelEXSIDE (blue).…”

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confidence: 99%

Pure-shift IMPRESS EXSIDE – Easy measurement of ¹H–¹³C scalar coupling constants with increased sensitivity and resolution

Ndukwe

2015

RSC Adv.

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The easy-to-interpret and rapid SelEXSIDE NMR experiment for measuring long-range NMR analyses of the 3D-structure of conformationally exible small molecules in solution are oen under-determined i.e. the stereochemistry or conformation cannot be denitively assigned because the number and accuracy of experimental parameters is too small to account for all of the possible congurations and conformations of the molecule. In organic molecules, 1 H-1 H scalar coupling constants ( 3 J HH ) and NOE measurements are the common NMR parameters used for this and are routinely combined with computational methods to improve structure elucidations or semi-quantitative methods exemplied by 'J-based congurational analysis' to acyclic systems. [1][2][3] We have recently demonstrated that increased accuracy in quantitative NOE-distance analysis of small molecules 4 allows ner details of dynamic 3D molecular structures to be resolved -for example identifying very small populations ($2%) of molecular conformers, 5 accurate determination of the rotational populations of a exible chain 6 and stereochemical elucidation of contiguous quaternary centres. 7Adding quantitative analysis of 2-and 3-bond 1 H-13 C scalar coupling constants ( n J CH ), of which there are many more than 3 J HH couplings in most organic molecules, enables even greater levels of discrimination such that we have successfully described the strong helical or linear conformational preference of iteratively homologated alkane diastereomers, despite thousands of potential conformers. challenging to accurately measure small coupling constants (<2 Hz) with this approach. An alternative approach to dealing with lineshape distortion is to use J-resolved approaches, exemplied by EXSIDE.12 Here the desired heteronuclear coupling constant is isolated and resolved as clean in-phase doublets in the indirect (vertical) F1 dimension of the spectrum (Fig. 1a). The F1-splitting of the peaks is the multiple of n J CH and a user-selected J-scaling factor, N. This provides an easy accurate means to measure even small n J CH values, down to $1 Hz in most cases. Such F1-based approaches, however, are relatively slow and weak and it generally requires several hours of measurement for each proton, while intensities are also reduced by T 2 relaxation in the extended J-scaled INEPT preparation period. The long experiment time arises because a large number of t 1 increments are needed to resolve small couplings in F1. Our recently reported 13 C band-selective EXSIDE 13 (SelEXSIDE) method substantially reduces the experiment time to just a few minutes by measuring each n J CH separately with a much narrower 13 C window, thus needing fewer t 1 increments. However the short experiment time also reduces signal averaging and thus sensitivity, so in

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SelEXSIDE: Fast and Easy Measurement of Multiple-Bond ¹H,¹³C Coupling Constants for Stereochemical Analysis

Cited by 20 publications

References 19 publications

Measurement of long‐range heteronuclear coupling constants using the peak intensity in classical 1D HMBC spectra

Measurement of long‐range heteronuclear coupling constants using the peak intensity in classical 1D HMBC spectra

¹H, ¹³C and ¹⁵N NMR spectral analysis of substituted 1,2,3,4‐tetrahydro‐pyrido[1,2‐a]pyrimidines

Pure-shift IMPRESS EXSIDE – Easy measurement of ¹H–¹³C scalar coupling constants with increased sensitivity and resolution

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SelEXSIDE: Fast and Easy Measurement of Multiple-Bond 1H,13C Coupling Constants for Stereochemical Analysis

Cited by 20 publications

References 19 publications

Measurement of long‐range heteronuclear coupling constants using the peak intensity in classical 1D HMBC spectra

Measurement of long‐range heteronuclear coupling constants using the peak intensity in classical 1D HMBC spectra

1H, 13C and 15N NMR spectral analysis of substituted 1,2,3,4‐tetrahydro‐pyrido[1,2‐a]pyrimidines

Pure-shift IMPRESS EXSIDE – Easy measurement of 1H–13C scalar coupling constants with increased sensitivity and resolution

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Product

Resources

About

SelEXSIDE: Fast and Easy Measurement of Multiple-Bond ¹H,¹³C Coupling Constants for Stereochemical Analysis

¹H, ¹³C and ¹⁵N NMR spectral analysis of substituted 1,2,3,4‐tetrahydro‐pyrido[1,2‐a]pyrimidines

Pure-shift IMPRESS EXSIDE – Easy measurement of ¹H–¹³C scalar coupling constants with increased sensitivity and resolution