Premium
Effect of the solvent on the conformation of monocrotaline as determined by isotropic and anisotropic NMR parameters
Author(s) -
Melo Sousa Cleyton Marcos,
Giordani Raquel Brandt,
Almeida Wamberto Alristenio Moreira,
Griesinger Christian,
Gil Roberto R.,
NavarroVázquez Armando,
Hallwass Fernando
Publication year - 2021
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.4968
Subject(s) - chemistry , pyrrolizidine , solvent , solvent polarity , anisotropy , ring (chemistry) , pyrrolizidine alkaloid , isotropy , two dimensional nuclear magnetic resonance spectroscopy , crystallography , proton nmr , stereochemistry , nuclear magnetic resonance , organic chemistry , physics , quantum mechanics
The conformation in solution of monocrotaline, a pyrrolizidine alkaloid presenting an eleven‐membered macrocyclic diester ring, has been investigated using a combination of isotropic and anisotropic nuclear magnetic resonance parameters measured in four solvents of different polarity (D 2 O, DMSO‐ d 6 , CDCl 3 , and C 6 D 6 ). Anisotropic nuclear magnetic resonance parameters were measured in different alignment media, based on their compatibility with the solvent of interest: cromoglycate liquid crystal solution was used for D 2 O, whereas a poly (methyl methacrylate) polymer gel was chosen for CDCl 3 and C 6 D 6 , and a poly (hydroxyethyl methacrylate) gel for DMSO‐ d 6 . Whereas the pyrrolizidine ring shows an E 6 exo ‐puckered conformation in all of the solvents, the macrocyclic eleven‐membered ring adopts different populations of syn ‐parallel and anti ‐parallel relative orientation of the carbonyl groups according to the polarity of the solvent.