organic compounds
of xerophenone A
aX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia, bNatural Products Research Laboratory, School of Science, Mae Fah Luang University, Tasud, Muang Chiang Rai 57100, Thailand, and cCrystal Materials Research Unit, Department of Chemistry, Faculty of Science, Prince of Songkla University, Hat-Yai, Songkhla 90112, Thailand
*Correspondence e-mail: hkfun@usm.my
The title compound, C33H42O5, known as xerophenone A {systematic name: (1R,3R,4R,6S,8E,10R)-10-hydroxy-8-[hydroxy(phenyl)methylene]-4-methyl-1,6-bis(3-methylbut-2-en-1-yl)-3-(3-methylbut-3-en-1-yl)-11-oxatricyclo[4.3.1.14,10]undecane-7,9-dione} is a naturally occurring rearranged benzophenone compound which was isolated from the twigs of Garcinia propinqua. The was determined by refining the to 0.18 (16). The absolute configurations at positions 1, 3, 4, 6 and 10 of the xerophenone A are R, R, R, S and R. In the molecule, the cyclohexane-1,3-dione, tetrahydro-2H-pyran and tetrahydrofuran rings adopt twisted boat, standard chair and envelope conformations, respectively. The 3-methylbut-3-en-1-yl substituent is disordered over two sets of sites in a 0.771 (11):0.229 (11) ratio. An intramolecular O—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, molecules are linked by O—H⋯O and weak C—H⋯O interactions into a chain along the a axis. A very weak C—H⋯π interaction and C⋯O short contact [2.989 (2) Å] are also present.
Related literature
For bond-length data, see: Allen et al. (1987). For ring conformations, see: Cremer & Pople (1975). For hydrogen-bond motifs, see: Bernstein et al. (1995). For background to plants in the Clusiaceae family, bioactive metabolites and their biological and pharmacological activities, see: Castardo et al. (2008); Henry & Jacobs (1995); Nguyen et al. (2011); Phongpaichit et al. (1994); Suksamrarn et al. (2006); Thoison et al. (2005); Xu et al. (2010); Yu et al. (2007). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986).
Experimental
Crystal data
|
Data collection: APEX2 (Bruker, 2009); cell SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009).
Supporting information
10.1107/S1600536812015267/is5112sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536812015267/is5112Isup2.hkl
Supporting information file. DOI: 10.1107/S1600536812015267/is5112Isup3.cml
Twigs of G. propinqua (1.90 Kg) were successively extracted with acetone over the period of 3 days at room temperature to provide the crude acetone extract (183.72g) which was subjected to quick α]D29 -21.2 (c 0.400, CH3OH)].
over silica gel and eluted by gradients of EtOAc-hexanes (100% hexanes to 100% EtOAc) to yield fourteen fractions (A-N). Fraction B (268.0 mg) was subjected to sephadex LH-20 using CH3OH as to afford compound (I) (21.8 mg) as white solid. Colorless plate-shaped single crystals of the title compound suitable for x-ray were recrystallized from CH2Cl2:acetone (1:1 v/v) by the slow evaporation of the solvent at room temperature after several days, m.p. 451.0-452.4 K [[H atoms were placed in calculated positions with d(O—H) = 0.82 Å, and d(C—H) = 0.93 Å for aromatic and CH, 0.97 Å for CH2 and 0.96 Å for CH3 atoms. The Uiso(H) values were constrained to be 1.5Ueq of the
for methyl H atoms and 1.2Ueq for the remaining H atoms. A rotating group model was used for the methyl groups. The 3-methyl-3-buten-1-yl substituent was found to be disordered over two sites in a 0.771 (11): 0.229 (11) occupancy ratio. In the final distance restraints were used for the disordered components. 2079 Friedel pairs were used to determine the absolute configuration.Data collection: APEX2 (Bruker, 2009); cell
SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).C33H42O5 | F(000) = 560 |
Mr = 518.67 | Dx = 1.186 Mg m−3 |
Monoclinic, P21 | Melting point = 451.0–452.4 K |
Hall symbol: P 2yb | Cu Kα radiation, λ = 1.54178 Å |
a = 6.1984 (2) Å | Cell parameters from 4746 reflections |
b = 17.0998 (4) Å | θ = 3.2–67.5° |
c = 13.7007 (3) Å | µ = 0.62 mm−1 |
β = 91.036 (1)° | T = 100 K |
V = 1451.92 (7) Å3 | Plate, colorless |
Z = 2 | 0.31 × 0.13 × 0.09 mm |
Bruker APEX Duo CCD area detector diffractometer | 4746 independent reflections |
Radiation source: sealed tube | 4661 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.023 |
ϕ and ω scans | θmax = 67.5°, θmin = 3.2° |
Absorption correction: multi-scan (SADABS; Bruker, 2009) | h = −6→7 |
Tmin = 0.830, Tmax = 0.944 | k = −19→20 |
11622 measured reflections | l = −16→16 |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.037 | H-atom parameters constrained |
wR(F2) = 0.099 | w = 1/[σ2(Fo2) + (0.0526P)2 + 0.4822P] where P = (Fo2 + 2Fc2)/3 |
S = 1.07 | (Δ/σ)max = 0.001 |
4746 reflections | Δρmax = 0.24 e Å−3 |
369 parameters | Δρmin = −0.20 e Å−3 |
7 restraints | Absolute structure: Flack (1983), 2079 Friedel pairs |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: 0.18 (16) |
C33H42O5 | V = 1451.92 (7) Å3 |
Mr = 518.67 | Z = 2 |
Monoclinic, P21 | Cu Kα radiation |
a = 6.1984 (2) Å | µ = 0.62 mm−1 |
b = 17.0998 (4) Å | T = 100 K |
c = 13.7007 (3) Å | 0.31 × 0.13 × 0.09 mm |
β = 91.036 (1)° |
Bruker APEX Duo CCD area detector diffractometer | 4746 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2009) | 4661 reflections with I > 2σ(I) |
Tmin = 0.830, Tmax = 0.944 | Rint = 0.023 |
11622 measured reflections |
R[F2 > 2σ(F2)] = 0.037 | H-atom parameters constrained |
wR(F2) = 0.099 | Δρmax = 0.24 e Å−3 |
S = 1.07 | Δρmin = −0.20 e Å−3 |
4746 reflections | Absolute structure: Flack (1983), 2079 Friedel pairs |
369 parameters | Absolute structure parameter: 0.18 (16) |
7 restraints |
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K. |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
O1 | −0.2134 (2) | 0.52353 (8) | 0.24048 (11) | 0.0296 (3) | |
H1O1 | −0.1378 | 0.5351 | 0.2881 | 0.084 (13)* | |
O2 | 0.0272 (2) | 0.50870 (8) | 0.38262 (10) | 0.0262 (3) | |
O3 | −0.2215 (2) | 0.27900 (8) | 0.24870 (9) | 0.0200 (3) | |
O4 | 0.4496 (2) | 0.36790 (8) | 0.32243 (9) | 0.0208 (3) | |
H1O4 | 0.5236 | 0.3382 | 0.2901 | 0.031* | |
O5 | 0.4021 (2) | 0.26998 (8) | 0.43398 (9) | 0.0198 (3) | |
C1 | 0.1716 (3) | 0.38478 (11) | 0.43458 (13) | 0.0191 (4) | |
C2 | 0.0072 (3) | 0.33858 (11) | 0.49672 (13) | 0.0191 (4) | |
H2A | −0.0471 | 0.3725 | 0.5474 | 0.023* | |
H2B | −0.1140 | 0.3231 | 0.4553 | 0.023* | |
C3 | 0.1071 (3) | 0.26536 (11) | 0.54423 (13) | 0.0212 (4) | |
H3A | 0.2122 | 0.2833 | 0.5936 | 0.025* | |
C4 | 0.2327 (3) | 0.21824 (11) | 0.46743 (14) | 0.0205 (4) | |
C5 | 0.1006 (3) | 0.20180 (11) | 0.37297 (13) | 0.0193 (4) | |
H5A | −0.0517 | 0.1970 | 0.3867 | 0.023* | |
H5B | 0.1491 | 0.1541 | 0.3421 | 0.023* | |
C6 | 0.1428 (3) | 0.27366 (11) | 0.30699 (13) | 0.0184 (4) | |
C7 | −0.0628 (3) | 0.31594 (11) | 0.27620 (12) | 0.0192 (4) | |
C8 | −0.0625 (3) | 0.40194 (12) | 0.28183 (13) | 0.0210 (4) | |
C9 | 0.0452 (3) | 0.43657 (12) | 0.36486 (14) | 0.0212 (4) | |
C10 | 0.2965 (3) | 0.32512 (11) | 0.37240 (13) | 0.0189 (4) | |
C11 | 0.3343 (3) | 0.43234 (12) | 0.49784 (14) | 0.0229 (4) | |
H11A | 0.4442 | 0.3969 | 0.5228 | 0.027* | |
H11B | 0.4050 | 0.4699 | 0.4561 | 0.027* | |
C12 | 0.2397 (3) | 0.47577 (11) | 0.58299 (14) | 0.0236 (4) | |
H12A | 0.0954 | 0.4903 | 0.5773 | 0.028* | |
C13 | 0.3434 (3) | 0.49531 (12) | 0.66554 (14) | 0.0251 (4) | |
C14 | 0.2342 (4) | 0.53943 (14) | 0.74493 (15) | 0.0340 (5) | |
H14A | 0.0824 | 0.5428 | 0.7303 | 0.051* | |
H14B | 0.2938 | 0.5912 | 0.7495 | 0.051* | |
H14C | 0.2563 | 0.5127 | 0.8059 | 0.051* | |
C15 | 0.5786 (4) | 0.47874 (14) | 0.68566 (16) | 0.0320 (5) | |
H15A | 0.6407 | 0.4549 | 0.6293 | 0.048* | |
H15B | 0.5926 | 0.4439 | 0.7404 | 0.048* | |
H15C | 0.6525 | 0.5268 | 0.7002 | 0.048* | |
C16 | −0.0659 (3) | 0.21819 (12) | 0.59759 (14) | 0.0262 (4) | |
H16A | −0.0041 | 0.1691 | 0.6200 | 0.031* | |
H16B | −0.1835 | 0.2062 | 0.5524 | 0.031* | |
C17 | −0.1550 (4) | 0.26321 (14) | 0.68556 (17) | 0.0355 (5) | |
H17A | −0.0353 | 0.2846 | 0.7222 | 0.043* | |
H17B | −0.2138 | 0.3120 | 0.6628 | 0.043* | 0.771 (12) |
H17C | −0.2384 | 0.3065 | 0.6610 | 0.043* | 0.229 (12) |
C18A | −0.3256 (9) | 0.2211 (3) | 0.7408 (5) | 0.0243 (12) | 0.771 (12) |
C19A | −0.5160 (5) | 0.2548 (3) | 0.7573 (2) | 0.0322 (9) | 0.771 (12) |
H19A | −0.6209 | 0.2279 | 0.7916 | 0.038 (9)* | 0.771 (12) |
H19B | −0.5436 | 0.3051 | 0.7345 | 0.051 (11)* | 0.771 (12) |
C20A | −0.2778 (9) | 0.1407 (2) | 0.7766 (3) | 0.0546 (17) | 0.771 (12) |
H20A | −0.3932 | 0.1230 | 0.8168 | 0.082* | 0.771 (12) |
H20B | −0.1454 | 0.1410 | 0.8141 | 0.082* | 0.771 (12) |
H20C | −0.2637 | 0.1060 | 0.7219 | 0.082* | 0.771 (12) |
C18B | −0.289 (2) | 0.2169 (14) | 0.7528 (18) | 0.036 (7)* | 0.229 (12) |
C19B | −0.500 (2) | 0.2237 (11) | 0.7641 (10) | 0.035 (4)* | 0.229 (12) |
H19C | −0.5694 | 0.1940 | 0.8110 | 0.043* | 0.229 (12) |
H19D | −0.5794 | 0.2582 | 0.7250 | 0.043* | 0.229 (12) |
C20B | −0.162 (2) | 0.1622 (9) | 0.8146 (11) | 0.052 (4)* | 0.229 (12) |
H20D | −0.2429 | 0.1489 | 0.8714 | 0.078* | 0.229 (12) |
H20E | −0.0289 | 0.1866 | 0.8343 | 0.078* | 0.229 (12) |
H20F | −0.1321 | 0.1156 | 0.7781 | 0.078* | 0.229 (12) |
C21 | 0.2596 (3) | 0.25027 (11) | 0.21211 (14) | 0.0206 (4) | |
H21A | 0.2787 | 0.2968 | 0.1727 | 0.025* | |
H21B | 0.4020 | 0.2307 | 0.2296 | 0.025* | |
C22 | 0.1440 (3) | 0.18912 (12) | 0.15065 (14) | 0.0223 (4) | |
H22A | −0.0018 | 0.1809 | 0.1619 | 0.027* | |
C23 | 0.2358 (3) | 0.14645 (12) | 0.08194 (13) | 0.0230 (4) | |
C24 | 0.4683 (3) | 0.15337 (14) | 0.05475 (15) | 0.0299 (5) | |
H24A | 0.5413 | 0.1878 | 0.0997 | 0.045* | |
H24B | 0.4776 | 0.1740 | −0.0102 | 0.045* | |
H24C | 0.5348 | 0.1027 | 0.0574 | 0.045* | |
C25 | 0.1098 (4) | 0.08582 (15) | 0.02536 (17) | 0.0353 (5) | |
H25A | −0.0395 | 0.0887 | 0.0425 | 0.053* | |
H25B | 0.1649 | 0.0348 | 0.0408 | 0.053* | |
H25C | 0.1235 | 0.0954 | −0.0433 | 0.053* | |
C26 | 0.3406 (3) | 0.14549 (12) | 0.50876 (14) | 0.0245 (4) | |
H26A | 0.4467 | 0.1271 | 0.4640 | 0.037* | |
H26B | 0.2341 | 0.1056 | 0.5182 | 0.037* | |
H26C | 0.4093 | 0.1578 | 0.5702 | 0.037* | |
C27 | −0.1913 (3) | 0.44964 (11) | 0.22138 (14) | 0.0222 (4) | |
C28 | −0.3061 (3) | 0.42365 (12) | 0.13087 (14) | 0.0239 (4) | |
C29 | −0.5102 (4) | 0.45424 (13) | 0.11046 (16) | 0.0297 (5) | |
H29A | −0.5735 | 0.4887 | 0.1539 | 0.036* | |
C30 | −0.6192 (4) | 0.43302 (14) | 0.02479 (17) | 0.0358 (5) | |
H30A | −0.7562 | 0.4530 | 0.0116 | 0.043* | |
C31 | −0.5257 (4) | 0.38254 (15) | −0.04068 (17) | 0.0389 (6) | |
H31A | −0.5993 | 0.3686 | −0.0978 | 0.047* | |
C32 | −0.3208 (4) | 0.35257 (14) | −0.02083 (16) | 0.0345 (5) | |
H32A | −0.2572 | 0.3186 | −0.0649 | 0.041* | |
C33 | −0.2112 (3) | 0.37321 (13) | 0.06458 (14) | 0.0277 (4) | |
H33A | −0.0740 | 0.3533 | 0.0775 | 0.033* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0378 (9) | 0.0196 (7) | 0.0313 (8) | 0.0031 (6) | −0.0018 (6) | 0.0021 (6) |
O2 | 0.0342 (8) | 0.0176 (7) | 0.0269 (7) | −0.0002 (6) | 0.0027 (6) | −0.0030 (5) |
O3 | 0.0167 (6) | 0.0210 (6) | 0.0224 (6) | −0.0012 (5) | 0.0026 (5) | −0.0013 (5) |
O4 | 0.0187 (7) | 0.0196 (6) | 0.0243 (6) | −0.0022 (5) | 0.0074 (5) | −0.0035 (5) |
O5 | 0.0166 (6) | 0.0207 (7) | 0.0223 (6) | 0.0002 (5) | 0.0019 (5) | −0.0005 (5) |
C1 | 0.0195 (9) | 0.0175 (9) | 0.0204 (8) | −0.0018 (7) | 0.0036 (7) | −0.0037 (7) |
C2 | 0.0202 (9) | 0.0171 (9) | 0.0201 (8) | −0.0001 (7) | 0.0051 (6) | −0.0024 (7) |
C3 | 0.0223 (10) | 0.0205 (9) | 0.0210 (9) | −0.0002 (7) | 0.0017 (7) | −0.0001 (7) |
C4 | 0.0201 (10) | 0.0197 (9) | 0.0218 (9) | −0.0013 (7) | 0.0016 (7) | 0.0000 (7) |
C5 | 0.0205 (10) | 0.0164 (9) | 0.0209 (8) | −0.0004 (7) | 0.0019 (7) | −0.0020 (7) |
C6 | 0.0172 (9) | 0.0184 (9) | 0.0198 (8) | −0.0014 (7) | 0.0038 (6) | −0.0007 (7) |
C7 | 0.0199 (10) | 0.0234 (9) | 0.0145 (8) | −0.0001 (7) | 0.0053 (7) | 0.0013 (7) |
C8 | 0.0174 (9) | 0.0232 (9) | 0.0228 (9) | −0.0007 (7) | 0.0060 (7) | 0.0013 (7) |
C9 | 0.0186 (9) | 0.0210 (9) | 0.0244 (9) | −0.0015 (7) | 0.0092 (7) | 0.0007 (8) |
C10 | 0.0181 (10) | 0.0190 (9) | 0.0196 (8) | −0.0005 (7) | 0.0031 (7) | −0.0011 (7) |
C11 | 0.0214 (10) | 0.0221 (9) | 0.0252 (9) | −0.0027 (8) | 0.0019 (7) | −0.0052 (8) |
C12 | 0.0235 (10) | 0.0188 (10) | 0.0284 (10) | 0.0026 (7) | 0.0032 (8) | −0.0027 (8) |
C13 | 0.0316 (11) | 0.0196 (10) | 0.0243 (10) | 0.0016 (8) | 0.0016 (8) | 0.0009 (8) |
C14 | 0.0441 (14) | 0.0328 (12) | 0.0251 (10) | 0.0078 (10) | −0.0014 (9) | −0.0042 (9) |
C15 | 0.0347 (12) | 0.0320 (12) | 0.0292 (11) | 0.0016 (9) | −0.0029 (8) | −0.0030 (9) |
C16 | 0.0297 (11) | 0.0235 (10) | 0.0255 (10) | 0.0005 (8) | 0.0059 (8) | 0.0035 (8) |
C17 | 0.0407 (13) | 0.0322 (12) | 0.0339 (11) | −0.0022 (10) | 0.0106 (9) | −0.0004 (9) |
C18A | 0.031 (2) | 0.025 (2) | 0.0165 (18) | −0.0018 (15) | 0.0026 (18) | −0.0019 (11) |
C19A | 0.0319 (18) | 0.038 (3) | 0.0267 (16) | −0.0004 (15) | 0.0072 (11) | −0.0064 (16) |
C20A | 0.087 (4) | 0.037 (2) | 0.041 (2) | 0.011 (2) | 0.033 (2) | 0.0124 (16) |
C21 | 0.0172 (9) | 0.0237 (9) | 0.0210 (9) | −0.0006 (7) | 0.0048 (7) | −0.0036 (7) |
C22 | 0.0203 (10) | 0.0227 (9) | 0.0240 (9) | −0.0014 (7) | 0.0041 (7) | −0.0022 (8) |
C23 | 0.0240 (10) | 0.0250 (10) | 0.0201 (9) | 0.0006 (8) | 0.0005 (7) | 0.0000 (8) |
C24 | 0.0273 (11) | 0.0349 (12) | 0.0277 (10) | 0.0016 (9) | 0.0058 (8) | −0.0083 (9) |
C25 | 0.0318 (12) | 0.0401 (13) | 0.0342 (11) | −0.0028 (10) | 0.0039 (9) | −0.0155 (10) |
C26 | 0.0242 (10) | 0.0239 (10) | 0.0255 (9) | 0.0009 (8) | 0.0017 (7) | 0.0006 (8) |
C27 | 0.0227 (10) | 0.0204 (10) | 0.0238 (9) | −0.0027 (7) | 0.0080 (7) | 0.0024 (7) |
C28 | 0.0262 (10) | 0.0213 (10) | 0.0243 (9) | −0.0018 (8) | 0.0029 (7) | 0.0065 (8) |
C29 | 0.0303 (11) | 0.0275 (11) | 0.0313 (11) | 0.0010 (8) | 0.0029 (8) | 0.0084 (8) |
C30 | 0.0304 (12) | 0.0370 (12) | 0.0396 (12) | −0.0026 (10) | −0.0070 (9) | 0.0169 (10) |
C31 | 0.0451 (14) | 0.0426 (14) | 0.0286 (10) | −0.0095 (10) | −0.0082 (9) | 0.0071 (10) |
C32 | 0.0458 (14) | 0.0330 (12) | 0.0248 (10) | −0.0021 (10) | 0.0010 (9) | 0.0008 (9) |
C33 | 0.0300 (11) | 0.0273 (10) | 0.0258 (9) | −0.0016 (8) | 0.0034 (8) | 0.0035 (8) |
O1—C27 | 1.298 (2) | C17—C18A | 1.497 (4) |
O1—H1O1 | 0.8200 | C17—H17A | 0.9602 |
O2—C9 | 1.262 (2) | C17—H17B | 0.9603 |
O3—C7 | 1.223 (2) | C17—H17C | 0.9603 |
O4—C10 | 1.389 (2) | C18A—C19A | 1.336 (6) |
O4—H1O4 | 0.8200 | C18A—C20A | 1.488 (6) |
O5—C10 | 1.417 (2) | C19A—H19A | 0.9300 |
O5—C4 | 1.454 (2) | C19A—H19B | 0.9300 |
C1—C9 | 1.511 (3) | C20A—H20A | 0.9600 |
C1—C10 | 1.546 (2) | C20A—H20B | 0.9600 |
C1—C11 | 1.549 (2) | C20A—H20C | 0.9600 |
C1—C2 | 1.555 (2) | C18B—C19B | 1.324 (12) |
C2—C3 | 1.536 (3) | C18B—C20B | 1.479 (12) |
C2—H2A | 0.9700 | C19B—H19C | 0.9300 |
C2—H2B | 0.9700 | C19B—H19D | 0.9300 |
C3—C16 | 1.537 (3) | C20B—H20D | 0.9600 |
C3—C4 | 1.546 (3) | C20B—H20E | 0.9600 |
C3—H3A | 0.9800 | C20B—H20F | 0.9600 |
C4—C26 | 1.517 (3) | C21—C22 | 1.515 (3) |
C4—C5 | 1.544 (2) | C21—H21A | 0.9700 |
C5—C6 | 1.551 (3) | C21—H21B | 0.9700 |
C5—H5A | 0.9700 | C22—C23 | 1.327 (3) |
C5—H5B | 0.9700 | C22—H22A | 0.9300 |
C6—C7 | 1.519 (3) | C23—C24 | 1.499 (3) |
C6—C21 | 1.552 (2) | C23—C25 | 1.505 (3) |
C6—C10 | 1.566 (2) | C24—H24A | 0.9600 |
C7—C8 | 1.473 (3) | C24—H24B | 0.9600 |
C8—C27 | 1.402 (3) | C24—H24C | 0.9600 |
C8—C9 | 1.436 (3) | C25—H25A | 0.9600 |
C11—C12 | 1.510 (3) | C25—H25B | 0.9600 |
C11—H11A | 0.9700 | C25—H25C | 0.9600 |
C11—H11B | 0.9700 | C26—H26A | 0.9600 |
C12—C13 | 1.333 (3) | C26—H26B | 0.9600 |
C12—H12A | 0.9300 | C26—H26C | 0.9600 |
C13—C14 | 1.496 (3) | C27—C28 | 1.487 (3) |
C13—C15 | 1.506 (3) | C28—C33 | 1.391 (3) |
C14—H14A | 0.9600 | C28—C29 | 1.393 (3) |
C14—H14B | 0.9600 | C29—C30 | 1.392 (3) |
C14—H14C | 0.9600 | C29—H29A | 0.9300 |
C15—H15A | 0.9600 | C30—C31 | 1.380 (4) |
C15—H15B | 0.9600 | C30—H30A | 0.9300 |
C15—H15C | 0.9600 | C31—C32 | 1.392 (4) |
C16—C17 | 1.541 (3) | C31—H31A | 0.9300 |
C16—H16A | 0.9700 | C32—C33 | 1.388 (3) |
C16—H16B | 0.9700 | C32—H32A | 0.9300 |
C17—C18B | 1.483 (11) | C33—H33A | 0.9300 |
C27—O1—H1O1 | 109.5 | H16A—C16—H16B | 107.9 |
C10—O4—H1O4 | 109.5 | C18B—C17—C16 | 115.6 (12) |
C10—O5—C4 | 105.31 (13) | C18A—C17—C16 | 114.9 (3) |
C9—C1—C10 | 107.31 (14) | C18B—C17—H17A | 108.5 |
C9—C1—C11 | 111.77 (16) | C18A—C17—H17A | 117.7 |
C10—C1—C11 | 109.10 (15) | C16—C17—H17A | 108.3 |
C9—C1—C2 | 107.87 (15) | C18B—C17—H17B | 116.8 |
C10—C1—C2 | 107.82 (14) | C18A—C17—H17B | 108.4 |
C11—C1—C2 | 112.76 (15) | C16—C17—H17B | 108.6 |
C3—C2—C1 | 112.52 (15) | H17A—C17—H17B | 97.1 |
C3—C2—H2A | 109.1 | C18B—C17—H17C | 108.9 |
C1—C2—H2A | 109.1 | C18A—C17—H17C | 99.7 |
C3—C2—H2B | 109.1 | C16—C17—H17C | 108.0 |
C1—C2—H2B | 109.1 | H17A—C17—H17C | 107.2 |
H2A—C2—H2B | 107.8 | C19A—C18A—C20A | 121.0 (3) |
C2—C3—C16 | 110.48 (16) | C19A—C18A—C17 | 120.8 (4) |
C2—C3—C4 | 109.89 (15) | C20A—C18A—C17 | 118.2 (4) |
C16—C3—C4 | 114.47 (16) | C18A—C19A—H19A | 120.0 |
C2—C3—H3A | 107.2 | C18A—C19A—H19B | 120.0 |
C16—C3—H3A | 107.2 | H19A—C19A—H19B | 120.0 |
C4—C3—H3A | 107.2 | C19B—C18B—C20B | 120.4 (12) |
O5—C4—C26 | 107.49 (15) | C19B—C18B—C17 | 126.3 (12) |
O5—C4—C5 | 102.80 (14) | C20B—C18B—C17 | 113.1 (10) |
C26—C4—C5 | 112.76 (16) | C18B—C19B—H19C | 120.0 |
O5—C4—C3 | 105.83 (14) | C18B—C19B—H19D | 120.0 |
C26—C4—C3 | 113.40 (15) | H19C—C19B—H19D | 120.0 |
C5—C4—C3 | 113.54 (15) | C18B—C20B—H20D | 109.5 |
C4—C5—C6 | 104.59 (14) | C18B—C20B—H20E | 109.5 |
C4—C5—H5A | 110.8 | H20D—C20B—H20E | 109.5 |
C6—C5—H5A | 110.8 | C18B—C20B—H20F | 109.5 |
C4—C5—H5B | 110.8 | H20D—C20B—H20F | 109.5 |
C6—C5—H5B | 110.8 | H20E—C20B—H20F | 109.5 |
H5A—C5—H5B | 108.9 | C22—C21—C6 | 114.87 (15) |
C7—C6—C5 | 112.93 (15) | C22—C21—H21A | 108.6 |
C7—C6—C21 | 106.98 (14) | C6—C21—H21A | 108.6 |
C5—C6—C21 | 111.73 (16) | C22—C21—H21B | 108.6 |
C7—C6—C10 | 112.97 (15) | C6—C21—H21B | 108.6 |
C5—C6—C10 | 102.64 (14) | H21A—C21—H21B | 107.5 |
C21—C6—C10 | 109.64 (14) | C23—C22—C21 | 124.69 (18) |
O3—C7—C8 | 122.18 (17) | C23—C22—H22A | 117.7 |
O3—C7—C6 | 120.41 (17) | C21—C22—H22A | 117.7 |
C8—C7—C6 | 117.41 (16) | C22—C23—C24 | 124.00 (18) |
C27—C8—C9 | 118.67 (18) | C22—C23—C25 | 121.25 (19) |
C27—C8—C7 | 123.35 (17) | C24—C23—C25 | 114.76 (17) |
C9—C8—C7 | 116.96 (17) | C23—C24—H24A | 109.5 |
O2—C9—C8 | 120.92 (18) | C23—C24—H24B | 109.5 |
O2—C9—C1 | 119.83 (17) | H24A—C24—H24B | 109.5 |
C8—C9—C1 | 119.16 (17) | C23—C24—H24C | 109.5 |
O4—C10—O5 | 109.37 (15) | H24A—C24—H24C | 109.5 |
O4—C10—C1 | 106.11 (15) | H24B—C24—H24C | 109.5 |
O5—C10—C1 | 109.97 (14) | C23—C25—H25A | 109.5 |
O4—C10—C6 | 115.32 (14) | C23—C25—H25B | 109.5 |
O5—C10—C6 | 103.67 (14) | H25A—C25—H25B | 109.5 |
C1—C10—C6 | 112.36 (14) | C23—C25—H25C | 109.5 |
C12—C11—C1 | 115.64 (16) | H25A—C25—H25C | 109.5 |
C12—C11—H11A | 108.4 | H25B—C25—H25C | 109.5 |
C1—C11—H11A | 108.4 | C4—C26—H26A | 109.5 |
C12—C11—H11B | 108.4 | C4—C26—H26B | 109.5 |
C1—C11—H11B | 108.4 | H26A—C26—H26B | 109.5 |
H11A—C11—H11B | 107.4 | C4—C26—H26C | 109.5 |
C13—C12—C11 | 126.22 (18) | H26A—C26—H26C | 109.5 |
C13—C12—H12A | 116.9 | H26B—C26—H26C | 109.5 |
C11—C12—H12A | 116.9 | O1—C27—C8 | 120.55 (18) |
C12—C13—C14 | 121.73 (19) | O1—C27—C28 | 114.10 (17) |
C12—C13—C15 | 123.94 (19) | C8—C27—C28 | 125.31 (18) |
C14—C13—C15 | 114.29 (18) | C33—C28—C29 | 119.70 (19) |
C13—C14—H14A | 109.5 | C33—C28—C27 | 121.89 (19) |
C13—C14—H14B | 109.5 | C29—C28—C27 | 118.34 (18) |
H14A—C14—H14B | 109.5 | C30—C29—C28 | 119.8 (2) |
C13—C14—H14C | 109.5 | C30—C29—H29A | 120.1 |
H14A—C14—H14C | 109.5 | C28—C29—H29A | 120.1 |
H14B—C14—H14C | 109.5 | C31—C30—C29 | 120.5 (2) |
C13—C15—H15A | 109.5 | C31—C30—H30A | 119.7 |
C13—C15—H15B | 109.5 | C29—C30—H30A | 119.7 |
H15A—C15—H15B | 109.5 | C30—C31—C32 | 119.7 (2) |
C13—C15—H15C | 109.5 | C30—C31—H31A | 120.1 |
H15A—C15—H15C | 109.5 | C32—C31—H31A | 120.1 |
H15B—C15—H15C | 109.5 | C33—C32—C31 | 120.2 (2) |
C3—C16—C17 | 111.89 (17) | C33—C32—H32A | 119.9 |
C3—C16—H16A | 109.2 | C31—C32—H32A | 119.9 |
C17—C16—H16A | 109.2 | C32—C33—C28 | 120.1 (2) |
C3—C16—H16B | 109.2 | C32—C33—H33A | 120.0 |
C17—C16—H16B | 109.2 | C28—C33—H33A | 119.9 |
C9—C1—C2—C3 | 160.42 (15) | C2—C1—C10—C6 | 56.49 (19) |
C10—C1—C2—C3 | 44.83 (19) | C7—C6—C10—O4 | −91.58 (18) |
C11—C1—C2—C3 | −75.68 (19) | C5—C6—C10—O4 | 146.50 (15) |
C1—C2—C3—C16 | −175.28 (15) | C21—C6—C10—O4 | 27.6 (2) |
C1—C2—C3—C4 | −48.0 (2) | C7—C6—C10—O5 | 148.89 (14) |
C10—O5—C4—C26 | 163.91 (14) | C5—C6—C10—O5 | 26.98 (17) |
C10—O5—C4—C5 | 44.74 (17) | C21—C6—C10—O5 | −91.90 (17) |
C10—O5—C4—C3 | −74.61 (16) | C7—C6—C10—C1 | 30.2 (2) |
C2—C3—C4—O5 | 61.30 (18) | C5—C6—C10—C1 | −91.72 (17) |
C16—C3—C4—O5 | −173.72 (15) | C21—C6—C10—C1 | 149.40 (16) |
C2—C3—C4—C26 | 178.88 (16) | C9—C1—C11—C12 | 78.7 (2) |
C16—C3—C4—C26 | −56.1 (2) | C10—C1—C11—C12 | −162.80 (16) |
C2—C3—C4—C5 | −50.7 (2) | C2—C1—C11—C12 | −43.0 (2) |
C16—C3—C4—C5 | 74.3 (2) | C1—C11—C12—C13 | 153.3 (2) |
O5—C4—C5—C6 | −25.42 (17) | C11—C12—C13—C14 | 179.2 (2) |
C26—C4—C5—C6 | −140.85 (15) | C11—C12—C13—C15 | 2.0 (3) |
C3—C4—C5—C6 | 88.42 (18) | C2—C3—C16—C17 | −66.0 (2) |
C4—C5—C6—C7 | −122.38 (16) | C4—C3—C16—C17 | 169.32 (16) |
C4—C5—C6—C21 | 116.96 (16) | C3—C16—C17—C18B | −168.3 (8) |
C4—C5—C6—C10 | −0.44 (18) | C3—C16—C17—C18A | 179.6 (3) |
C5—C6—C7—O3 | −44.1 (2) | C18B—C17—C18A—C19A | 137 (8) |
C21—C6—C7—O3 | 79.2 (2) | C16—C17—C18A—C19A | −126.4 (5) |
C10—C6—C7—O3 | −160.05 (15) | C18B—C17—C18A—C20A | −43 (7) |
C5—C6—C7—C8 | 135.35 (16) | C16—C17—C18A—C20A | 53.4 (6) |
C21—C6—C7—C8 | −101.31 (18) | C18A—C17—C18B—C19B | −21 (5) |
C10—C6—C7—C8 | 19.4 (2) | C16—C17—C18B—C19B | −110 (3) |
O3—C7—C8—C27 | −28.6 (3) | C18A—C17—C18B—C20B | 163 (9) |
C6—C7—C8—C27 | 151.94 (17) | C16—C17—C18B—C20B | 74 (2) |
O3—C7—C8—C9 | 139.71 (18) | C7—C6—C21—C22 | −67.3 (2) |
C6—C7—C8—C9 | −39.8 (2) | C5—C6—C21—C22 | 56.8 (2) |
C27—C8—C9—O2 | −1.0 (3) | C10—C6—C21—C22 | 169.87 (15) |
C7—C8—C9—O2 | −169.84 (17) | C6—C21—C22—C23 | −161.87 (19) |
C27—C8—C9—C1 | 175.66 (16) | C21—C22—C23—C24 | −0.6 (3) |
C7—C8—C9—C1 | 6.8 (2) | C21—C22—C23—C25 | 178.91 (19) |
C10—C1—C9—O2 | −141.69 (17) | C9—C8—C27—O1 | −0.3 (3) |
C11—C1—C9—O2 | −22.1 (2) | C7—C8—C27—O1 | 167.77 (18) |
C2—C1—C9—O2 | 102.38 (19) | C9—C8—C27—C28 | 177.48 (17) |
C10—C1—C9—C8 | 41.6 (2) | C7—C8—C27—C28 | −14.4 (3) |
C11—C1—C9—C8 | 161.21 (16) | O1—C27—C28—C33 | 137.03 (19) |
C2—C1—C9—C8 | −74.29 (19) | C8—C27—C28—C33 | −40.9 (3) |
C4—O5—C10—O4 | −168.82 (14) | O1—C27—C28—C29 | −39.7 (3) |
C4—O5—C10—C1 | 75.03 (16) | C8—C27—C28—C29 | 142.3 (2) |
C4—O5—C10—C6 | −45.31 (16) | C33—C28—C29—C30 | 1.2 (3) |
C9—C1—C10—O4 | 67.41 (17) | C27—C28—C29—C30 | 177.98 (19) |
C11—C1—C10—O4 | −53.85 (18) | C28—C29—C30—C31 | −0.7 (3) |
C2—C1—C10—O4 | −176.63 (14) | C29—C30—C31—C32 | 0.1 (3) |
C9—C1—C10—O5 | −174.40 (15) | C30—C31—C32—C33 | 0.1 (4) |
C11—C1—C10—O5 | 64.34 (18) | C31—C32—C33—C28 | 0.3 (3) |
C2—C1—C10—O5 | −58.44 (18) | C29—C28—C33—C32 | −1.0 (3) |
C9—C1—C10—C6 | −59.47 (19) | C27—C28—C33—C32 | −177.67 (19) |
C11—C1—C10—C6 | 179.27 (15) |
Cg4 is the centroid of the C28–C33 ring. |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1O1···O2 | 0.82 | 1.70 | 2.4446 (19) | 151 |
O4—H1O4···O3i | 0.82 | 1.97 | 2.7499 (18) | 159 |
C21—H21B···O3i | 0.97 | 2.48 | 3.283 (2) | 139 |
C25—H25B···Cg4ii | 0.96 | 2.99 | 3.786 (3) | 142 |
Symmetry codes: (i) x+1, y, z; (ii) −x, y−1/2, −z. |
Experimental details
Crystal data | |
Chemical formula | C33H42O5 |
Mr | 518.67 |
Crystal system, space group | Monoclinic, P21 |
Temperature (K) | 100 |
a, b, c (Å) | 6.1984 (2), 17.0998 (4), 13.7007 (3) |
β (°) | 91.036 (1) |
V (Å3) | 1451.92 (7) |
Z | 2 |
Radiation type | Cu Kα |
µ (mm−1) | 0.62 |
Crystal size (mm) | 0.31 × 0.13 × 0.09 |
Data collection | |
Diffractometer | Bruker APEX Duo CCD area detector diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 2009) |
Tmin, Tmax | 0.830, 0.944 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 11622, 4746, 4661 |
Rint | 0.023 |
(sin θ/λ)max (Å−1) | 0.599 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.037, 0.099, 1.07 |
No. of reflections | 4746 |
No. of parameters | 369 |
No. of restraints | 7 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.24, −0.20 |
Absolute structure | Flack (1983), 2079 Friedel pairs |
Absolute structure parameter | 0.18 (16) |
Computer programs: APEX2 (Bruker, 2009), SAINT (Bruker, 2009), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).
Cg4 is the centroid of the C28–C33 ring. |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1O1···O2 | 0.82 | 1.70 | 2.4446 (19) | 151 |
O4—H1O4···O3i | 0.82 | 1.97 | 2.7499 (18) | 159 |
C21—H21B···O3i | 0.97 | 2.48 | 3.283 (2) | 139 |
C25—H25B···Cg4ii | 0.96 | 2.99 | 3.786 (3) | 142 |
Symmetry codes: (i) x+1, y, z; (ii) −x, y−1/2, −z. |
Acknowledgements
SL and CT are grateful to the Thailand Research Fund and Mae Fah Luang University for financial support. The authors thank Prince of Songkla University for financial support through the Crystal Materials Research Unit and Universiti Sains Malaysia for the Research University Grant No. 1001/PFIZIK/811160. We thank Assoc. Professor Dr Chatchanok Karalai for useful discussions.
References
Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–19. CrossRef Web of Science Google Scholar
Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555–1573. CrossRef CAS Web of Science Google Scholar
Bruker (2009). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Castardo, J. C., Prudente, A. S., Ferreira, J., Guimaraes, C. L., Monache, F. D., Filho, V. C., Otuki, M. F. & Cabrini, D. A. (2008). J. Ethnopharmacol. 118, 405–411. Web of Science CrossRef PubMed CAS Google Scholar
Cosier, J. & Glazer, A. M. (1986). J. Appl. Cryst. 19, 105–107. CrossRef CAS Web of Science IUCr Journals Google Scholar
Cremer, D. & Pople, J. A. (1975). J. Am. Chem. Soc. 97, 1354–1358. CrossRef CAS Web of Science Google Scholar
Flack, H. D. (1983). Acta Cryst. A39, 876–881. CrossRef CAS Web of Science IUCr Journals Google Scholar
Henry, G. E. & Jacobs, H. (1995). Tetrahedron Lett. 36, 4575–4578. CrossRef CAS Web of Science Google Scholar
Nguyen, H. D., Trinh, B. T. D., Tran, Q. N., Nguyen, H. D., Pham, H. D., Hansen, P. E., Duus, F., Connolly, J. D. & Nguyen, L.-H. D. (2011). Phytochemistry, 72, 290–295. Web of Science CrossRef CAS PubMed Google Scholar
Phongpaichit, S., Ongsakul, M., Nilrat, L., Tharavichitkul, P., Bunchoo, S., Chauprapaisilp, T. & Wiriyachitra, P. (1994). Songklanakarin J. Sci. Technol. 16, 399–405. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar
Suksamrarn, S., Komutiban, O., Ratananukul, P., Chimnoi, N., Lartpornmatulee, N. & Suksamrarn, A. (2006). Chem. Pharm. Bull. 54, 301–305. Web of Science CrossRef PubMed CAS Google Scholar
Thoison, O., Cuong, D. D., Gramain, A., Chiaroni, A., Hung, N. V. & Sevenet, T. (2005). Tetrahedron, 61, 8529–8535. Web of Science CSD CrossRef CAS Google Scholar
Xu, G., Kan, W. L. T., Zhou, Y., Song, J. Z., Han, Q. B., Qiao, C. F., Cho, C. H., Rudd, J. A., Lin, G. & Xu, H. X. (2010). J. Nat. Prod. 73, 104–108. Web of Science CrossRef CAS PubMed Google Scholar
Yu, L., Zhao, M., Yang, B., Zhao, Q. & Jiang, Y. (2007). Food Chem. 104, 176–181. Web of Science CrossRef CAS Google Scholar
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Garcinia belongs to the Clusiaceae family which is well recognized to produce a variety of biological active metabolites including xanthones (Phongpaichit et al., 1994), flavanones (Castardo et al., 2008), terpenoids (Nguyen et al., 2011) and benzophenones (Thoison et al., 2005; Xu et al., 2010). Several of these compounds possess interesting biological and pharmacological activities, such as antimicrobial (Xu et al., 2010), antidepressant and anti-HIV (Xu et al., 2010), antioxidant (Yu et al., 2007) and also cytotoxic (Suksamrarn et al., 2006) activities. During the course of our study of bioactive compounds from medicinal plants, the title compound (I), known as xerophenone A (Henry & Jacobs, 1995) was isolated from the twigs of G. propinqua which were collected from Chiang Rai province in the northern part of Thailand. Herein the crystal structure and absolute configuration of (I) was reported.
The title compound (I), C33H42O5, is a rearranged benzophenone and an isoprenylated derivative of 11-oxatricyclo[4.3.1.14,10]undecane-7,9-dione. Figure 1 shows that (I) exists in an E configuration with respect to the C8═C27 double bond [1.402 (3) Å] with a C9–C8–C27–C28 torsion angle 177.48 (17)°. In order to view more clearly and gain more information of the ring conformations and the orientations of the rings and how each substituent is in respect to the bound rings, Figure 2 is also shown. It can be clearly seen that the cyclohexane-1,3-dione ring is in a twisted boat with the puckering parameters Q = 0.616 (2) Å, θ = 101.86 (19)° and ϕ = 157.84 (19)° (Cremer & Pople, 1975), the tetrahydro-2H-pyran ring (C1–C4/C10/O5) is in a standard chair conformation and the tetrahydrofuran ring (C4–C6/C10/O5) is in an envelope conformation with the puckering atom O5 of 0.283 (1) Å, and puckering parameter Q = 0.4223 (18) Å and ϕ = 1.0 (3)°. The two 3-methyl-2-buten-1-yl substituents (C11–C15 and C21–C15) are attached to the cyclohexane-1,3-dione moiety at atoms C1 and C6 with the torsion angles C1—C11—C12–C13 = 153.3 (2)° and C6–C21–C22–C23 = -161.87 (19)°, indicating a (+)-anti-periplanar and (-)-anti-periplanar conformations, respectively. The 3-methyl-3-buten-1-yl substituent (C16–C20) is disordered over two positions in a 0.771 (11): 0.229 (11) ratio, and attached to the tetrahydro-2H-pyran ring at atom C3 with the torsion angles C3–C16–C17–C18 = 179.6 (3)° for the major component (A) and -168.3 (8)° for the minor component (B) (Fig. 1). An intramolecular O1—H1O1···O2 hydrogen bond (Table 1) generates an S(6) ring motif (Bernstein et al., 1995). The bond distances in (I) are within normal ranges (Allen et al., 1987). The absolute configuration at atoms C1, C3, C4, C6 and C10 or at positions 1, 3, 4, 6 and 10 of the xerophenone A are R,R,R,S,R configurations.
In the crystal (Fig. 3), molecules are linked by O—H···O hydrogen bonds and weak C—H···O interactions (Table 1) forming an R21(7) motif which connected the molecules into a chain along the a axis. A C—H···π interaction (Table 1) and a C27···O4i short contact [2.989 (2) Å] are observed.