Ent-Isocopal-12-ene-15,16-dialdehyde fromSpongia officinalis

Abstract

The X-ray analysis of the natural product ent-isocopal-12-ene-15,16-dialdehyde, 1,4,4a,4b,5,6,7,8,8a,9,10,10a-dodecahydro-4b,8,8,10a-tetramethyl-1,2-phenanthrene-dicarboxaldehyde, C 20 H 30 O 2 , is reported. The compound was isolated, together with other diterpenes of the spongian type, from the diethyl ether soluble fraction of Spongia officinalis [Cimino, Morrone & Sodano (1982). Tetrahedron Lett. 23, 4139-4142] and characterized. In the asymmetric unit, there are two molecules showing high geometrical and conformational similarity. The C-20 diterpenoid presents a trans-fused tricyclic system with a 1,4-dialdehyde function, adjacent to the double bond of the cyclohexene ring. Short intramolecular contacts, especially between the axial and isooriented methyl groups, cause significant distortions in the ring skeleton similar to that observed in other correlated structures. The profile of the molecule is rather bent (radius of curvature about 13 A) in the direction perpendicular to the averaged molecular plane. Similar bending has been observed in the correlated scalaradial and 12-deacetoxyscalaradial structures and helps to improve the intramolecular interactions.