Determination of the Absolute Configuration of Aegelinol by Crystallization of Its Inclusion Complex with β-Cyclodextrin

The absolute configuration and structure of aegelinol, a pyranocoumarin isolated from Ferulago asparagifolia Boiss (Apiaceae), has been determined by crystallography. Crystal structure of the inclusion complex of aegelinol in β-cyclodextrin was determined (a = 15.404(1) Å, b = 15.281(1) Å, c = 17.890(1) Å, α = 99.662(1), β = 113.4230(1), γ = 102.481(1)°, P1; R1 = 6.71%) and allowed unambiguous determination of the absolute configuration of the stereogenic center of aegelinol. The pyranocoumarin guest is included within the cylindrical cavity formed by dimeric β-cyclodextrin molecules with a head-to-head arrangement. Crystal structure of aegelinol alone was also determined (a = 6.8921(3) Å, b = 11.4302(9) Å, c = 44.964(3) Å, P212121; R1 = 4.44%) and allowed precise determination of its geometry. Aegelinol crystallizes with three molecules in the asymmetric unit held together by H-bonds and π-stacking interactions. OPEN ACCESS Crystals 2012, 2 1442