title: The distorted tropane of scopoline.
abstract: The structural isomerization of scopine into scopoline (oscine) has been observed in a supersonic jet expansion using microwave spectroscopy. The rotational spectrum evidences a single structure in the gas phase, providing a first description of the (three-ring) structurally distorted tropane in scopoline. The absence of rotational signatures of any scopine conformation suggests a practically quantitative isomerization at the vaporization temperatures of the experiment (ca. 90 °C). The determined rotational parameters of scopoline reveal the structural consequences of the intramolecular cyclation of scopine, which breaks the original epoxy group and creates a new ether bridge and a 7β-hydroxytropane configuration. The hydroxy group further stabilizes the molecule by an O-H⋅⋅⋅N intramolecular hydrogen bond, which, in turn, forces the N-methyl group to the less stable axial form. Supporting ab initio (MP2) and DFT (B3LYP, M06-2X) calculations are included.
authors: Departamento de Química Física, Facultad de Ciencia y Tecnología, Universidad del País Vasco (UPV-EHU), Apartado 644, 48080 Bilbao, Spain.
authors: Patricia
authors: P
authors: Écija
authors: Emilio J
authors: EJ
authors: Cocinero
authors: Alberto
authors: A
authors: Lesarri
authors: Francisco J
authors: FJ
authors: Basterretxea
authors: José A
authors: JA
authors: Fernández
authors: Fernando
authors: F
authors: Castaño
mesh_terms: D003374:Coumarins / Q000737:chemistry*; D005740:Gases / Q000737:chemistry; D005960:Glucosides / Q000737:chemistry*; D006860:Hydrogen Bonding; D007536:Isomerism; D008872:Microwaves; D012399:Rotation; D014326:Tropanes / Q000737:chemistry*
chemical_list: D003374:Coumarins; D005740:Gases; D005960:Glucosides; D014326:Tropanes; C417572:scopolin