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Abstract 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 (D₂O, DMSO‐d₆, CDCl₃, and C₆D₆). 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 D₂O, whereas a poly (methyl methacrylate) polymer gel was chosen for CDCl₃and C₆D₆, and a poly (hydroxyethyl methacrylate) gel for DMSO‐d₆. Whereas the pyrrolizidine ring shows anE₆exo‐puckered conformation in all of the solvents, the macrocyclic eleven‐membered ring adopts different populations ofsyn‐parallel andanti‐parallel relative orientation of the carbonyl groups according to the polarity of the solvent.