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Abstract We present a method to use long‐range CH coupling constants to derive the correct diastereoisomer from the molecular constitution of small molecules. A set of 792JCHand3JCHvalues collected from a single HSQMBC experiment on a sample of strychnine were used in the CASE‐3D (computer‐assisted 3D structure elucidation) protocol. In addition to the most commonly used3JCHcoupling constants, the subset of 322JCHvalues alone showed an excellent degree of configuration selection. The study is mainly based on comparison of DFT‐calculated2,3JCHvalues with experimental ones, critical for the case of2JCH. But the configuration selection also works well using3JCHvalues predicted from a semi‐empirical Karplus‐based equation limited to H−C−C−C fragments. The robustness, shown using strychnine as a proof of concept, makes theJ‐based CASE‐3D analysis a viable option for the application in fields such as peptide and carbohydrate research, organic synthesis, natural‐product identification and analysis, as well as medicinal chemistry.
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DFT investigation of coupling constant anomalies in substituted β‐lactams
Abstract β‐lactams are a chemically diverse group of molecules with a wide range of biological activities. Having recently observed curious trends in2JHHcoupling values in studies on this structural class, we sought to obtain a more comprehensive understanding of these diagnostic NMR parameters, specifically interrogating1JCH,2JCH, and2JHH, to differentiate 3‐ and 4‐monosubstituted β‐lactams. Further investigation using computational chemistry methods was employed to explore the geometric and electronic origins for the observed and calculated differences between the two substitution patterns.
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- Award ID(s):
- 2116395
- PAR ID:
- 10643501
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Magnetic Resonance in Chemistry
- Volume:
- 62
- Issue:
- 8
- ISSN:
- 0749-1581
- Format(s):
- Medium: X Size: p. 573-582
- Size(s):
- p. 573-582
- Sponsoring Org:
- National Science Foundation
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