Crystal and molecular structure of melampodin B, a 4,5-cis-9,10-trans-germacranolide sesquiterpene dilactone
Abstract
The crystal and molecular structure of melampodin B, C17H18O7, has been determined by single crystal X-ray diffraction. Crystals are monoclinic, P21, a= 9.714(4), b= 6.922(1), c= 12.503(1)Å, β= 106.76(1)°, Z= 2. The structure was refined to an R value of 3.0% over 1 871 total reflections. The cyclodeca-4,5-cis-9,10-trans-diene ring is in a conformation theoretically derivable from a cyclodeca-4,5-cis-1,10-cis-diene precursor, as determined by empirical force field calculations. Lactone rings are fused to the cyclodecadiene at C(6)–C(7) and at C(8)–C(10). Intermolecular hydrogen bonds between the hydroxy group and a lactone carbonyl oxygen atom link molecules in the solid.