The crystal structure and absolute configuration of the 3-p-iodobenzoate-11-acetate of secogorgosterol

The crystal and molecular structure of a cyclopropane containing marine steroid, secogorgosterol and its absolute configuration have been determined by single X-ray diffraction studies on the 3-p-iodobenzoate-11-acetate derivative. The compound crystallizes in space group PI with reduced cell dimensions a = 9.58, b = 16.38, c = 9.80, α = 96.71, β = 139.75, γ = 94.29. There is one formula unit (C39H55O5I) per unit cell (Z = I). Crystal data were obtained on a G.E. XRD-5 diffractometer using the moving-crystal, moving-counter method, and the structure refined by least squares methods to a conventional R of 6.7% on all (2409) data. The structure determination confirms the presence of a cyclopropane ring in the side chain of the gorgosterol system while a trans conformation is observed about the 22-23 bond.