title: Structure and absolute configuration of ginkgolide B characterized by IR- and VCD spectroscopy.
abstract: Experimental and calculated (B3LYP/6-31G(d)) vibrational circular dichroism (VCD) and IR spectra are compared, illustrating that the structure and absolute configuration of ginkgolide B (GB) may be characterized directly in solution. A conformational search for GB using MacroModel and subsequent DFT optimizations (B3LYP/6-31G(d)) provides a structure for the lowest energy conformer which agrees well with the structure determined by X-ray diffraction. In addition, a conformer at an energy of 7 kJ mol(-1) (B3LYP/6-311+G(2d,2p)) with respect to the lowest energy conformer is predicted, displaying different intramolecular hydrogen bonding. Differences between measured and calculated IR and VCD spectra for GB at certain wavenumbers are rationalized in terms of interactions with solvent, intermolecular GB-GB interactions, and the potential presence of more than one conformer. This is the first detailed investigation of the spectroscopic fingerprint region (850-1300 cm(-1)) of the natural product GB employing infrared absorption and VCD spectroscopy.
authors.affiliation: Department of Physics, Quantum Protein Center (QuP), Technical University of Denmark, Kgs. Lyngby, Denmark.
authors.forename: Niels H
authors.initials: NH
authors.lastname: Andersen
authors.forename: Niels Johan
authors.initials: NJ
authors.lastname: Christensen
authors.forename: Peter R
authors.initials: PR
authors.lastname: Lassen
authors.forename: Teresa B N
authors.initials: TB
authors.lastname: Freedman
authors.forename: Laurence A
authors.initials: LA
authors.lastname: Nafie
authors.forename: Kristian
authors.initials: K
authors.lastname: Strømgaard
authors.forename: Lars
authors.initials: L
authors.lastname: Hemmingsen
mesh_terms: D002942:Circular Dichroism / Q000379:methods*; D046934:Ginkgolides / Q000737:chemistry*; D006860:Hydrogen Bonding; D007783:Lactones / Q000737:chemistry*; D008968:Molecular Conformation; D013055:Spectrophotometry, Infrared / Q000379:methods*
chemical_list: D046934:Ginkgolides; D007783:Lactones; C045856:ginkgolide B