81940-92-3Relevant academic research and scientific papers
Application of the Ecciton Method for the Stereochemical Assignment of Remote Groups. Determination of the α- or β-Configuration of a 2-Hydroxy-substituent in 2,17- and 2,16-Dihydroxy-A-nor-5α-androstane and -estrane Derivatives
Canceill, Josette,Collet, Andre,Jaques, Jean
, p. 83 - 90 (2007/10/02)
The c.d. of dibenzoate and bis-p-methoxybenzoate derivatives of 2,17- and 2,16-dihydroxy-A-nor-5α-androstanes and -estranes has been shown to arise principally from the coulombic coupling of the long-axis polarized excitation moments of the two benzoate groups.Analysis of the c.d. spectra in the light of the exciton chirality method allows an immediate determination of the α- or β-configuration of the 2-OH group, providing that the configuration of the 17- or 16-OH group is known.The c.d. spectra are qualitatively unaffected by the presence of additional ethynyl or methyl substituents in the molecule.The sign of the lower-energy component of the exciton c.d. couplet is given by the sign of the torsion angle θ=O(2)-C(2)-C(17)-O(17), or O(2)-C(2)-C(16)-O(16), the values of which can be deduced from X-ray data or Dreiding models.In spite of the weak coupling, due to the remoteness of the two interacting chromophores, observed and calculated rotational strengths are in fairly satisfactory agreement.
