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Issue 27, 2017
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Rotational spectra of tetracyclic quinolizidine alkaloids: does a water molecule flip sparteine?

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Abstract

Sparteine is a quinolizidine alkaloid used as a chiral auxiliary in asymmetric synthesis. We examine whether hydration by a single molecule can flip sparteine from the most stable trans conformation to the bidentate cis arrangement observed in catalytic complexation to a metal center. Sparteine and the sparteine–water dimer were generated in a supersonic jet expansion with H216O and H218O, and characterized by broadband chirped-pulse microwave spectroscopy. Even though the bidentate water dimer was predicted with larger binding energy, a single isomer was observed for the monohydrated cluster, with sparteine retaining the trans conformation observed for the free molecule. The absence of the bidentate dimer is attributed to the kinetic control of cluster formation, favoring the pre-expansion most abundant monomer. The structural properties of the O–H⋯N hydrogen bond in the dimer are compared with those of complexes of other secondary and tertiary amines.

Graphical abstract: Rotational spectra of tetracyclic quinolizidine alkaloids: does a water molecule flip sparteine?

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Publication details

The article was received on 06 Mar 2017, accepted on 15 Apr 2017 and first published on 05 May 2017


Article type: Paper
DOI: 10.1039/C7CP01432E
Citation: Phys. Chem. Chem. Phys., 2017,19, 17553-17559
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    Rotational spectra of tetracyclic quinolizidine alkaloids: does a water molecule flip sparteine?

    A. Lesarri, R. Pinacho, L. Enríquez, J. E. Rubio, M. Jaraíz, J. L. Abad and M. A. Gigosos, Phys. Chem. Chem. Phys., 2017, 19, 17553
    DOI: 10.1039/C7CP01432E

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