Abstract
The crystal structure of the title compound, C14H14N2O5, contains two distinct conformers in the asymmetric unit. The compound has three defined stereocenters, two of them contiguous, and a C=C double bond with an E conformation. The stereocenters exhibit the same chirality in both conformers, with significant differences in the conformation of the five-membered rings of the pyrrolizine unit (both either in a twist or in an envelope form) and in the dihedral angles between the corresponding mean planes and the benzene rings. A prominent feature is a change from almost coplanar rings in one conformer to a new conformation in the second conformer, in which the mean plane of a five-membered ring is almost perpendicular to the benzene ring, with a dihedral angle 87.19 (8)°; the corresponding angle in the first conformer is 14.02 (10)°. In the crystal, molecules are linked by O—H⋯O and C—H⋯O hydrogen bonds. Crystallographic data were essential to confirm the configuration of the double bond, which was unclear from the available two-dimensional NMR data. In addition, reliable Flack and Hooft parameters were obtained, allowing for the correct absolute structure to be determined.
Highlights
Laboratory of Synthesis of Natural Products and Drugs, Institute of Chemistry, University of Campinas, CP6154, CEP13083-970, Campinas, SP, Brazil
The stereocenters exhibit the same chirality in both conformers, with significant differences in the conformation of the five-membered rings of the pyrrolizine unit and in the dihedral angles between the corresponding mean planes and the benzene rings
A prominent feature is a change from almost coplanar rings in one conformer to a new conformation in the second conformer, in which the mean plane of a five-membered ring is almost perpendicular to the benzene ring, with a dihedral angle 87.19 (8) ; the corresponding angle in the first conformer is 14.02 (10)
Summary
F. Coelhob a Laboratory of Structural Biology and Crystallography, Institute of Chemistry, University of Campinas, CP6154, CEP13083-970, Campinas, SP, Brazil, and b. Laboratory of Synthesis of Natural Products and Drugs, Institute of Chemistry, University of Campinas, CP6154, CEP13083-970, Campinas, SP, Brazil. The crystal structure of the title compound, C14H14N2O5, contains two distinct conformers in the asymmetric unit. The compound has three defined stereocenters, two of them contiguous, and a C C double bond with an E conformation. The stereocenters exhibit the same chirality in both conformers, with significant differences in the conformation of the five-membered rings of the pyrrolizine unit (both either in a twist or in an envelope form) and in the dihedral angles between the corresponding mean planes and the benzene rings. Reliable Flack and Hooft parameters were obtained, allowing for the correct absolute structure to be determined
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