1984
DOI: 10.1002/mrc.1270220312
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A two‐dimensional NMR study of angelic and tiglic acid

Abstract: The controversy about the 13C NMR assignment of the methyl groups in angelates and tiglates was settled by two-dimensional 'H-=C chemical shift correlations for angelic and tiglic acid.

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Cited by 59 publications
(54 citation statements)
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“…This is clearly seen in the case of alkene 3 ac , for which both methyl groups show a hyperfine structure of a quartet due to mutual coupling with 5 J H,H =1.6 Hz. The high value measured for this coupling constant is really diagnostic, because, as reported for the Z and E isomers of 2‐butene and for isomeric tiglic acid and angelic acid, the cis arrangement ( Z olefin) consistently gives 5 J H,H constants of approximately 1.2 Hz (or even lower), whereas the trans E isomers show values identical to those here observed ( 5 J H,H =1.6 Hz) . In addition, the regiochemistry of 3 ab and 3 ae was determined on the basis of correlations observed in the 1 H– 13 C HMBC spectra.…”
Section: Resultssupporting
confidence: 61%
“…This is clearly seen in the case of alkene 3 ac , for which both methyl groups show a hyperfine structure of a quartet due to mutual coupling with 5 J H,H =1.6 Hz. The high value measured for this coupling constant is really diagnostic, because, as reported for the Z and E isomers of 2‐butene and for isomeric tiglic acid and angelic acid, the cis arrangement ( Z olefin) consistently gives 5 J H,H constants of approximately 1.2 Hz (or even lower), whereas the trans E isomers show values identical to those here observed ( 5 J H,H =1.6 Hz) . In addition, the regiochemistry of 3 ab and 3 ae was determined on the basis of correlations observed in the 1 H– 13 C HMBC spectra.…”
Section: Resultssupporting
confidence: 61%
“…angelic acid, was indicated by the chemical shift of the vinylic proton (H13) at 6.10 ppm rather than at about ca. δ 6.6 expected for the isomeric tiglic acid ( cis configuration of vinylic methyl groups) (Logie et al ., ) and the downfield shifts of the vinylic methyl carbons (Joseph‐Nathan et al ., ). Furthermore, NOESY correlations between H13 and both vinylic methyl groups (H14 and H15) also indicated a trans or E configuration of the methyl groups and hence angelic acid.…”
Section: Resultsmentioning
confidence: 97%
“…In addition, Me-14 (υ 0.95) showed correlation with the signal at υ 2.49, assigning this as H-9ˇ, and the signal at υ 2.49 as H-9˛. 20 Applying a MMFF energy cutoff of 10 kcal mol 1 and eliminating duplicate species, 15, 12, 17, and 12 conformations were found for 1-4, respectively, which were sorted according to their energy. All conformers were submitted to B3LYP/6-31G Ł DFT calculation.…”
Section: Resultsmentioning
confidence: 99%