Crystal and molecular structure of parthemollin {3,3a,4,5,6,8a-hexahydro-7-(1-hydroxy-3-oxobutyl)-6-methyl-3-methylenecyclohepta[b]-furan-2-one}

Abstract

The crystal structure of the title compound (I) has been determined from three-dimensional X-ray diffractometer data by direct methods. Crystals are monoclinic, space group P2₁, with Z= 2 in a cell of dimensions: a= 10·486(2), b= 6·581(3), c= 10·792(3)Å, β= 111·79(2)°. The positions of all hydrogens other than those of methyl and hydroxy-groups were found and the structure refined by least squares to R 0·091. The stereochemistry of the molecule has been established as having cis-fusion of the lactone ring, a result in contradiction to that suggested by an application of the Stöcklin–Waddell–Geissman rule of the lactone Cotton effect. Also Beecham's rule that the sign of the Cotton effect is determined by the chirality of the C:C·C:O chromophore is not valid in this case, the observed torsion angle being close to zero.