Sinularectin, a new diterpenoid from the soft coral Sinularia erecta Amira Rudi, a Guy Shmul, a Yehuda Benayahu b and Yoel Kashman a, * a School of Chemistry, Tel-Aviv University, Ramat Aviv 69978, Israel b Department of Zoology, Tel-Aviv University, Ramat Aviv 69978, Israel Received 21 December 2005; revised 15 February 2006; accepted 17 February 2006 Available online 10 March 2006 Abstract—A new norcembrane, designated sinularectin 3, was isolated from the Kenyan soft coral Sinularia erecta. Sinularectin is a chlorinated highly oxygenated norcembrane with an unprecedented functionalisation of the cembrane isopropyl group. The struc- ture of sinularectin was elucidated by interpretation of the HRESMS results as well as 1D and 2D NMR spectra. Ó 2006 Elsevier Ltd. All rights reserved. As part of our continuing program to discover bioactive compounds from marine invertebrates, we examined the Kenyan soft coral Sinularia erecta (Tixier-Durivault, 1945, family Alcyoniidae). Sinularia is among the most abundant soft coral genera on many soft coral reefs and it tends to form large monospecific ‘carpets’ of up to several square meters. 1,2 Previously, we investigated S. erecta samples collected from the Northern Red Sea 3 and the lagoon of Mayotte, in the Indo-Pacific. 4 The latter two samples, differing in the composition of their isoprenoids, afforded several sesquiterpenes, cem- branoids and C-4 norcembranoids. Variations in the chemical composition within specific soft corals is well known, yet the reason for this phenomenon is speculative 5 . The ethyl acetate/MeOH/H 2 O, 10:10:1, extract (750 mg) of the freeze-dried soft coral (15 g) 6 was solvent parti- tioned 7 and the CH 2 Cl 2 fraction was separated by chro- matography on Sephadex LH-20 (eluting with hexane/ CH 2 Cl 2 /MeOH, 2:1:1) to afford decaryiol 1 8 (6 mg), scabrolide A 2 9 (4 mg) and a new compound designated as sinularectin (3, 8 mg) (Fig. 1). Sinularectin 10 was ob- tained as a colourless oil. Its CIMS exhibited pseudomo- lecular ions at m/z 443/445 (3:1) consistent with the m/z 442/444 (3:1) peaks observed in the EIMS, thus suggest- ing a molecular formula of C 20 H 23 O 9 Cl. However, the HRESMS, together with the 13 C NMR data, established a formula of C 20 H 25 O 10 Cl with eight degrees of unsatu- ration. The ESMS spectrum exhibited peaks at 483.1033 [M+Na] + (calcd 483.1034) and 943.2170 [2M+Na], both in a cluster of peaks which are in full agreement with the calculated cluster for the suggested formula. The 13 C NMR spectrum of 3 contains two methyl groups, six methylenes, five methines and seven non-protonated carbon atoms, together accounting for 20 carbon atoms 0040-4039/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.tetlet.2006.02.118 * Corresponding author. Tel.: +972 3 6408419; fax: +972 3 6409293; e-mail: kashman@post.tau.ac.il O HO O O O CO 2 Me Cl O O H H 3 C O H H OH HO O O O H H H HO O H 1 14 2 15 17 19 12 11 10 18 8 6 5 3 scabrolide A 2 decaryiol 1 sinularectin 3 16 Figure 1. Tetrahedron Letters 47 (2006) 2937–2939