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The first quantitative determination of conformational equilibrium in quinolizidine-piperidine alkaloids

✍ Scribed by Tadeusz Brukwicki; Przybył Anna; Waleria Wysocka; Jacek Sośnicki

Publisher
Elsevier Science
Year
1999
Tongue
French
Weight
623 KB
Volume
55
Category
Article
ISSN
0040-4020

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✦ Synopsis

The fraction of the conformer with the boat ring C in the conformational equilibrium in N-methylangustifoline (7) in chloroform and benzene solutions was determined to be ca. 34% using coupling constant J7-13~3. In angustifoline (5) J7-131~ could not be determined directly from the spectra; a simulation gave the result of 4.25 Hz corresponding to ca. 23% of the boat conformer. In tetrahydrorhombifoline (6), rings B and C have a chair conformation. Low temperature ~3C NMR measurements seem to corroborate these results qualitatively. Factors influencing conformational equilibria are discussed.

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Assignment of the 1H and 13C NMR spectra
Assignment of the 1H and 13C NMR spectra of the quinolizidine alkaloid anagyrine and determination of its conformation
✍ David S. Rycroft; David J. Robins; Ian H. Sadler 📂 Article 📅 1991 🏛 John Wiley and Sons 🌐 English ⚖ 430 KB

## Abstract The ^1^H NMR spectrum of the quinolizidine alkaloid ( − )‐ anagyrine has been studied at 200 and 600 MHz. A full assignment of the ^1^H signals has been achieved by application of a variety of NMR techniques, including homo‐nuclear spin decoupling, NOE difference, 2D δ~H~/δ~H~ COSY and