2026-05-05T19:34:32Zhttps://uvadoc.uva.es/oai/request

oai:uvadoc.uva.es:10324/478302022-01-06T22:16:12Zcom_10324_28542com_10324_952com_10324_894col_10324_28543

Molecular rotation spectrum of tetracyclic quinolizidines: Observation of trans-Matrine and the elusive cis-Matrine Juanes San José, Marcos Saragi, Rizalina Tama Enríquez Giraudo, María Lourdes Jaraíz Maldonado, Martín Lesarri Gómez, Alberto Eugenio We characterized the bis-quinolizidine tetracyclic alkaloid (5S, 6S, 7R, 11R)-matrine in a supersonic jet expansion, using chirped-pulsed broadband microwave spectroscopy. Previous crystal diffraction analyses suggested 16 diastereoisomers associated with matrine’s four carbon stereocenters but were inconclusive whether the lactamic nitrogen atom would additionally produce separated trans-/cis- diastereoisomers or if both species may interconvert through low potential barriers. Our experiment simultaneously detected trans- and cis-matrine through their rotational spectrum, confirming the possibility of conformational rearrangement in matrine alkaloids. The two matrine conformers mainly differ in the envelope or half-chair lactamic ring, as evidenced by the experimental rotational and nuclear quadrupole coupling parameters. Molecular orbital calculations with ab initio (MP2) and density functional methods (B3LYP-D3(BJ) and MN15) were tested against the experiment, additionally offering an estimation of the cis-/trans- barrier of 24.9–26.9 kJ mol–1. The experiment illustrates the structural potential of chirped-pulsed broadband microwave spectroscopy for high-resolution rotational studies of biomolecules in the range of 20–40 atoms. 2021-07-30T08:21:58Z 2021-07-30T08:21:58Z 2021-07-30T08:21:58Z 2021 info:eu-repo/semantics/article The Journal of Organic Chemistry, 2021, vol. 86, n. 2. p. 1861–1867 1520-6904 https://uvadoc.uva.es/handle/10324/47830 10.1021/acs.joc.0c02689 eng https://pubs.acs.org/doi/10.1021/acs.joc.0c02689 info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by-nc-nd/4.0/ © 2021 ACS Publications Attribution-NonCommercial-NoDerivatives 4.0 Internacional ACS Publications