Abstract
AbstractThe X‐ray structure of 15‐apoviolaxanth‐15‐al ( = (1′S,2′R,4′S,2E,4E,6E,8E)‐9‐(1′,2′‐epoxy‐4′‐hydroxy‐2′,6′,6′‐trimethylcyclohexyl)‐3,7‐dimethylnona‐2,4,6,8‐tetraenal) is reported. The four symmetry‐independent molecules in the asymmetric unit are linked into X‐shaped spirals by intermolecular H‐bonds. Additional H‐bonds interconnect the spirals, forming wave‐like chains. The geometry of the polyene side chain possesses the same in‐plane bending observed for related retinal and carotenoid compounds. The polyene side chain deviates from planarity by twists of up to 10° about each bond; some of the largest twists are about CC bonds. The epoxycyclohexane ring possesses a distorted ‘C(3)‐sofa’ conformation. The torsion angles about the bond connecting the polyene chain to the cyclohexane ring are compared with equivalent torsion angles in molecules containing epoxide rings substituted with a π‐system in order to examine possible interactions between the epoxide group and the π‐system, either through pseudoconjugation, or through an interaction of the nonbonding orbitals of the epoxy O‐atom with the π‐orbitals of the polyene chain. The latter is considered to be more likely.
Published Version
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