X-Ray Structure of 8alpha-Acetoxy-1,3,4,10-Tetrahydro-1alpha,10alpha-Epoxyachillin

Abstract

(5aI-I,6/~-I, 11 aH)-8a-Acetoxy- 1,5-dihydro-2- oxo-lct,10ct-epoxyguaian-6,12-olide, C~7H2206, Mr= 322.3, orthorhombic P2~212~, a= 14.964(6), b= 17.057(4), c=6.218(4)A, V=1587(1)A 3, Z=4, D,n=l.349(5), D x=l.349Mgm -3, 2(MoKa)= 0.7107 A, # = 0.09 mm -l, F(000) = 688, room temperature, final wR--0.068 for 1899 observed reflexions. The conformations displayed by the cyclopentanone, y-lactone and cycloheptane rings are near to a twist, an envelope and a chair form, respectively. The cyclopentanone-cycloheptane and y-lactone-eycloheptane ring fusions are cis and trans, respectively. Packing in the crystal is due to weak C-H...O hydrogen-bond interactions giving chains of molecules parallel to [010] and [001].