Structure of Membranolide, a Diterpene from the Antarctic Sponge Dendrilla membranosa

Abstract

Methyl 2-[1,3-dihydro-3-oxo-5-(2,3,3- trimethylcyclohexyl)isobenzofuran-4-yl]propionate, C2~Hz804, Mr = 344"45, orthorhombic, P212121, a = 7.040(2), b= 14.238 (4), c= 18.810 (5) A, V = 1885.4 A 3, Z = 4, Dx = 1.214 Mg m -3, A(Mo Ka) = 0.71069A, /z =0.08mm-1, F(000)=744, T= 293 K, R= 0-050 for 1758 unique observed reflections. The structure consists of a cyclohexane ring in the chair conformation which possesses as substituents at C(4) two methyl groups, and at C(10) an equatorial methyl group, and in an axial position an isobenzofuranone ring with an a-(methoxycarbonyl) ethyl side chain. All bond lengths and angles are within the expected ranges.