A novel chlorinated norsesquiterpenoid and two related new metabolites from the soft coral Paralemnalia thyrsoides Ho-Cheng Huang, a,b Chih-Hua Chao, a Ju-Hsiou Liao, c Michael Y. Chiang, d Chang-Feng Dai, e Yang-Chang Wu f and Jyh-Horng Sheu a, * a Department of Marine Biotechnology and Resources, National Sun Yat-Sen University, Kaohsiung 804, Taiwan, ROC b Department of Chemical and Materials Engineering, Cheng Shiu University, Kaohsiung 833, Taiwan, ROC c Department of Chemistry, National Chung Cheng University, Chia-Yi 621, Taiwan, ROC d Department of Chemistry, National Sun Yat-Sen University, Kaohsiung 804, Taiwan, ROC e Institute of Oceanography, National Taiwan University, Taipei 106, Taiwan, ROC f Graduate Institute of Natural Products, Kaohsiung Medical University, Kaohsiung 807, Taiwan, ROC Received 12 August 2005; revised 6 September 2005; accepted 7 September 2005 Available online 23 September 2005 Abstract—A structurally unique chlorinated norsesquiterpenoid, paralemnolin A (1), along with two new metabolites, paralemnolin B(2) and C (3), have been isolated from the soft coral Paralemnalia thyrsoides. Their structures were determined by extensive spec- troscopic analyses. Single-crystal X-ray diffraction analysis of 1 further establish the absolute stereochemistry of 1. Ó 2005 Elsevier Ltd. All rights reserved. Soft coral of the genus Paralemnalia have been found to be a rich source of bioactive secondary metabo- lites. 1–4 During the course of our investigation on the bioactive chemical constituents from marine inverte- brates, 5–7 two new norsesquiterpenoids (1 and 2), and one sesquiterpenoid (3) have been isolated from the soft coral Paralemnalia thyrsoides, collected by hand using scuba at Green Island, located off the southeast coast of Taiwan. We describe herein the structure elucidation of these compounds, and also the proposed biosynthesis pathway for the chlorinated metabolite 1 (Fig. 1). The organism of P. thyrsoides was frozen immediately after collection and the freeze-dried organism was extracted sequentially with EtOAc. The EtOAc extract (33.0 g) was fractionated by open column chromatogra- phy on silica gel using n-hexane, n-hexane/EtOAc, and EtOAc/MeOH mixtures of increasing polarity. A frac- tion eluted with EtOAc/n-hexane (1:15) was further purified by normal-phase HPLC using EtOAc/n-hexane (1:50) to afford compound 1 (20.9 mg). Compounds 2 (27.3 mg) and 3 (35.5 mg) were eluted with EtOAc/ n-hexane (1:10) and further purified by normal-phase HPLC using EtOAc/n-hexane (1:30). ESIMS of paralemnolin A (1) 8 exhibited two ion peaks at m/z 277 [M+Na] + /279 [M+2+Na] + (in a ratio ca. 1:0.3) in accordance with the presence of one chlorine atom (Table 1). A molecular formula of C 14 H 19 ClO 2 for 1 was established by HRESIMS, indicating five de- grees of unsaturation. The NMR spectral data suggested the presence of one ketone (d C 206.6 qC), one 1-alkyl, 0040-4039/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.tetlet.2005.09.027 Keywords: Paralemnolin A; Paralemnolin B; Paralemnolin C; Para- lemnalia thyrsoides; Soft coral. * Corresponding author. Tel.: +886 7 5252000x5030; fax: +886 7 5255020; e-mail: sheu@mail.nsysu.edu.tw O O OH OH OAc OAc O Cl 1 2 3 4 1 4 7 10 11 12 13 14 1 4 5 7 10 11 12 13 14 15 O Figure 1. Structures of metabolites 1–4. Tetrahedron Letters 46 (2005) 7711–7714 Tetrahedron Letters