Curcumenol from Curcuma zedoaria:a second monoclinic modification Omer Abdalla Ahmed Hamdi, Khalijah Awang, A. Hamid A. Hadi, Devi Rosmy Syamsir and Seik Weng Ng* Department of Chemistry, University of Malaya, 50603 Kuala Lumpur, Malaysia Correspondence e-mail: seikweng@um.edu.my Received 7 October 2010; accepted 10 October 2010 Key indicators: single-crystal X-ray study; T = 100 K; mean (C–C) = 0.003 A ˚ ; R factor = 0.037; wR factor = 0.090; data-to-parameter ratio = 10.2. The title compound, systematic name 9-isopropylidene-2,6- dimethyl-11-oxatricyclo[6.2.1.0 1,5 ]undec-6-en-8-ol, C 15 H 22 O 2 , which crystallizes with two molecules of similar conformation in the asymmetric unit, features three fused rings, two of which are five-membered and the third six-membered. Of the two five-membered rings, the one with an O atom has a distinct envelope shape (with the O atom representing the flap). The six-membered ring is also envelope-shaped as it shares a common O atom with the five-membered ring. In the crystal, the two independent molecules are linked by a pair of O— HO hydrogen bonds, generating a dimer. Related literature For the C2 modification isolated from Globba malaccensis Ridl, see: Muangsin et al. (2004). Experimental Crystal data C 15 H 22 O 2 M r = 234.33 Monoclinic, P2 1 a = 9.3495 (7) A ˚ b = 12.535 (1) A ˚ c = 11.7727 (9) A ˚ = 96.532 (1) V = 1370.76 (18) A ˚ 3 Z =4 Mo K radiation = 0.07 mm 1 T = 100 K 0.40 0.05 0.05 mm Data collection Bruker SMART APEX diffractometer 13257 measured reflections 3298 independent reflections 2882 reflections with I >2(I) R int = 0.046 Refinement R[F 2 >2(F 2 )] = 0.037 wR(F 2 ) = 0.090 S = 1.03 3298 reflections 323 parameters 1 restraint H atoms treated by a mixture of independent and constrained refinement Á max = 0.21 e A ˚ 3 Á min = 0.18 e A ˚ 3 Table 1 Hydrogen-bond geometry (A ˚ , ). D—HA D—H HA DA D—HA O1—H1O4 0.89 (3) 1.92 (3) 2.799 (2) 168 (3) O3—H3O2 0.86 (3) 1.92 (3) 2.771 (2) 171 (3) Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X- SEED (Barbour, 2001); software used to prepare material for publication: publCIF (Westrip, 2010). We thank the University of Malaya for supporting this study. Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: HB5676). References Barbour, L. J. (2001). J. Supramol. Chem. 1, 189–191. Bruker (2009). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Muangsin, N., Ngamrojnavanich, N., Onanong, S., Chaichit, N., Roengsumran, S. & Petsom, A. (2004). J. Struct. Chem. 45, 293–297. Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. organic compounds o2844 Ahmed Hamdi et al. doi:10.1107/S1600536810040559 Acta Cryst. (2010). E66, o2844 Acta Crystallographica Section E Structure Reports Online ISSN 1600-5368