Novel methods of automated structure elucidation based on <sup>13</sup>C NMR spectroscopy

Meiler, Jens; Köck, Matthias

doi:10.1002/mrc.1424

Cited by 18 publications

(10 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…They compared the performance of this neural network method to that of the commonly used approaches utilizing additivity rules, fragment-based database searches, and quantum chemical calculations. In their article, Meiler and Köck [251] compare these three existing implementations using real molecules (a thiourea derivative, tryptophan, and prianosin D acetate) as examples. The results were comparable with those obtained using a five-sphere HOSE code prediction relying on the SPECINFO database.…”

Section: Computer-assisted Analysismentioning

confidence: 99%

15N NMR Spectroscopy in Structural Analysis: An Update (2001 - 2005)

Marek¹,

Lyčka²,

Kolehmainen³

et al. 2007

COC

131

114

View full text Add to dashboard Cite

Since our previous review article (Curr. Org. Chem. 2002, 6, 35), significant improvements and an array of 15 N NMR applications in structural analysis have been published. This report aims to update coverage of improvements in methodology and various types of applications published over the period 2001 -2005. Substantial progress in cryogenic probe technology and the commercial availability of cryoprobes have facilitated the measurement of 15 N NMR parameters.The number of solid-state applications has increased significantly during the past few years. In contrast to our previous review, this article covers 15 N solid-state studies. The 15 N NMR chemical shifts of organic molecules are routinely measured by using cross-polarization magic-angle spinning (CP/MAS) techniques. The principal values of the chemical shift tensors can also be determined. 1 H-15 N and 2 H-15 N distance measurements made by means of 1 H detection are currently used in NMR crystallography.User friendly quantum chemical programs allow for the routine calculation of 15 N chemical shielding and indirect spinspin coupling constants, especially using density functional theory (DFT).Applications of 15 N NMR spectroscopy in various fields of chemistry are summarized here. Major sections represent tautomerism, complexation, protonation, and hydrogen bonding. The other topics comprise N-alkylation, N-oxidation, regioisomerism, and changes in configuration or conformation.

show abstract

Section: Computer-assisted Analysismentioning

confidence: 99%

15N NMR Spectroscopy in Structural Analysis: An Update (2001 - 2005)

Marek¹,

Lyčka²,

Kolehmainen³

et al. 2007

COC

131

114

View full text Add to dashboard Cite

show abstract

“…For the small number of interesting constitutions a back-calculation on the carbon chemical shifts was made (ChemDraw v11), that were compared to the experimental values (see table 2). The last line in the table contains the sum of the absolute chemical shift differences for all carbons, exposing molecule 6 as the one that best fits the experimental data [24,27,28]. …”

Section: Resultsmentioning

confidence: 99%

Theoretical NMR correlations based Structure Discussion

Junker

2011

J Cheminform

View full text Add to dashboard Cite

The constitutional assignment of natural products by NMR spectroscopy is usually based on 2D NMR experiments like COSY, HSQC, and HMBC. The actual difficulty of the structure elucidation problem depends more on the type of the investigated molecule than on its size. The moment HMBC data is involved in the process or a large number of heteroatoms is present, a possibility of multiple solutions fitting the same data set exists. A structure elucidation software can be used to find such alternative constitutional assignments and help in the discussion in order to find the correct solution. But this is rarely done. This article describes the use of theoretical NMR correlation data in the structure elucidation process with WEBCOCON, not for the initial constitutional assignments, but to define how well a suggested molecule could have been described by NMR correlation data. The results of this analysis can be used to decide on further steps needed to assure the correctness of the structural assignment. As first step the analysis of the deviation of carbon chemical shifts is performed, comparing chemical shifts predicted for each possible solution with the experimental data. The application of this technique to three well known compounds is shown. Using NMR correlation data alone for the description of the constitutions is not always enough, even when including 13C chemical shift prediction.

show abstract

“…Since the solutions will then have to be checked manually for their chemical feasibility and sense, Different efforts have been made to reduce the number solutions. Among others, ranking of the constitutional assignments by chemical shift deviation and/or substructural elements have been tested [25,26] integrated to C OCON runs. Unfortunately, the described software could not be made available for the online version of C OCON ( WEB C OCON at http://cocon.nmr.de), since it uses data protected by Intellectual Property.…”

Section: Resultsmentioning

confidence: 99%

Statistical filtering for NMR based structure generation

Junker

2011

J Cheminform

View full text Add to dashboard Cite

The constitutional assignment of natural products by NMR spectroscopy is usually based on 2D NMR experiments like COSY, HSQC, and HMBC. The difficulty of a structure elucidation problem depends more on the type of the investigated molecule than on its size. Saturated compounds can usually be assigned unambiguously by hand using only COSY and 13C-HMBC data, whereas condensed heterocycles are problematic due to their lack of protons that could show interatomic connectivities. Different computer programs were developed to aid in the structural assignment process, one of them COCON. In the case of unsaturated and substituted molecules structure generators frequently will generate a very large number of possible solutions. This article presents a "statistical filter" for the reduction of the number of results. The filter works by generating 3D conformations using smi23d, a simple MD approach. All molecules for which the generation of constitutional restraints failed were eliminated from the result set. Some structural elements removed by the statistical filter were analyzed and checked against Beilstein. The automatic removal of molecules for which no MD parameter set could be created was included into WEBCOCON. The effect of this filter varies in dependence of the NMR data set used, but in no case the correct constitution was removed from the resulting set.

show abstract

Novel methods of automated structure elucidation based on ¹³C NMR spectroscopy

Cited by 18 publications

References 24 publications

15N NMR Spectroscopy in Structural Analysis: An Update (2001 - 2005)

15N NMR Spectroscopy in Structural Analysis: An Update (2001 - 2005)

Theoretical NMR correlations based Structure Discussion

Statistical filtering for NMR based structure generation

Contact Info

Product

Resources

About

Novel methods of automated structure elucidation based on 13C NMR spectroscopy

Cited by 18 publications

References 24 publications

15N NMR Spectroscopy in Structural Analysis: An Update (2001 - 2005)

15N NMR Spectroscopy in Structural Analysis: An Update (2001 - 2005)

Theoretical NMR correlations based Structure Discussion

Statistical filtering for NMR based structure generation

Contact Info

Product

Resources

About

Novel methods of automated structure elucidation based on ¹³C NMR spectroscopy