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The crystal structure of vulgarone B (2,6,6,11-tetra­methyl­tri­cyclo­[5.4.0.02,8]­undec-10-en-9-one), a carbocyclic sesquiterpene with the formula C15H22O, is reported. All intramolecular geometric parameters are as expected. The mol­ecule contains a four-membered ring, in which all atoms are stereogenic. The 1,3 and 2,4 atoms of this cyclo­butane are bridgehead C atoms which form part of six-membered and seven-membered rings.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536800020079/bt6000sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536800020079/bt6000Isup2.hkl
Contains datablock I

CCDC reference: 155906

Key indicators

  • Single-crystal X-ray study
  • T = 293 K
  • Mean [sigma](C-C) = 0.003 Å
  • Disorder in main residue
  • R factor = 0.050
  • wR factor = 0.132
  • Data-to-parameter ratio = 10.9

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


Red Alert Alert Level A:
TYPE_089 Alert A _refine_ls_abs_structure_Flack is not of type numb.
Author response: The refined value for the Flack parameter is nonsensical in the context of physically meaningful values for this variable [meaningful values are in the range 1 to 0, the refined result is -0.7 (6)]. Thus, it is listed in the main body of the cif as 'Not reliably determined' in keeping with examples culled from other Acta C publications. This is also addressed in the _publ_section_comment section.

Yellow Alert Alert Level C:
PLAT_301 Alert C Main residue disorder ........................ 16.00 Perc. General Notes
REFLT_03 From the CIF: _diffrn_reflns_theta_max 67.58 From the CIF: _reflns_number_total 1911 Count of symmetry unique reflns 1427 Completeness (_total/calc) 133.92% TEST3: Check Friedels for noncentro structure Estimate of Friedel pairs measured 484 Fraction of Friedel pairs measured 0.339 Are heavy atom types Z>Si present no WARNING: CuKa measured Friedel data can be used to determine absolute structure in a light-atom study only if the Friedel fraction is large.
1 Alert Level A = Potentially serious problem
0 Alert Level B = Potential problem
1 Alert Level C = Please check

Comment top

Continuing our structural and synthetic studies of the effects of ring strain on the properties of carbocyclic natural products (White & Lee, 1997), we report here the structure of vulgarone B, (I). This sesquiterpene was isolated as the major terpenoid component (ca 40%) of the essential oil of Artemisia douglasiana Bess., a plant that occurs widely in Western Oregon. An extract of this plant has been found to possess potent insecticidal and gastropod repellent activity. Previously, vulgarone B was isolated along with its isomer vulgarone A as a minor constituent of the oil of the medicinal plant Chrysanthemum vulgare (L.) Bernh, [Tanacetum vulgare (L)] (Uchio et al., 1977). It has also been obtained from the volatile oil of cultivars of Santolina chamaecyparcissus L. (Baig et al., 1989).

The structure of vulgarone B, including its absolute configuration, had earlier been deduced from spectroscopic evidence and by chemical correlation with the related sesquiterpene (+)-α-longipinene (Uchio, 1978). The results from our X-ray single-crystal diffraction experiment confirm the assigned structure. We also attempted to determine the absolute configuration of vulgarone B from the diffraction data, but, due to the small magnitude of the anomalous scattering components, the refined value of the absolute structure parameter could not be reliably determined. This is reflected in the fact that the model shown in Fig. 1 yields a value of -0.7 (6) for this parameter, whereas the inverted model yields a value of 1.7 (6). Further, since the absolute structure derived from the model shown is identical to the previously deduced configuration for this molecule (Uchio, 1978), we find it reasonable to conclude that this is the true configuration of vulgarone B.

All the observed intramolecular distances and angles are well within the expected values. The most interesting feature of the molecule is the four-membered ring, in which all four atoms are stereogenic. Opposite corners of this ring are the bridgehead C atoms that are components of two other rings, i.e. a seven-membered cycle and a six-membered ring. The six-membered ring contains a CC\sb CO moiety, which should force five of the six atoms in the ring to be planar. This is found to be correct; atoms O1, C1, C2, C3, C31, C4 and C11 are nearly coplanar, with a maximum deviation from the mean plane of 0.028 (2) Å by atom C2. This geometric constraint also causes a slight distortion of the four-membered ring, in which the bridgehead C atoms of the six-membered ring have moved toward each other. This is reflected in the C\sb C\sb C angles within the ring, which are identical pairwise at about 84 and 89° as shown in Table 1.

Experimental top

Crystals of the title compound were obtained by sublimation of a bulk sample under ambient pressure and temperature. Due to the high vapor pressure of the compound, it also sublimes during the diffraction experiment. Thus, in order to minimize the rate of sublimation, the crystal was completely encapsulated in a thin layer of epoxy glue. This strategy was sufficient to allow data collection over a period of a few days.

Refinement top

All data was employed in the refinement with the exception of the (1,1,2) reflection which had strongly negative intensity. During the course of the refinement, the disorder in the C(Me)2(CH2)3 backbone of the seven-membered ring became apparent. This disorder was modelled by introducing two (CH2)3 moieties anchored at both ends to the undisordered fragment of the molecule (C71/C81/C91 and C72/C82/C92), the occupation factors of which were allowed to refine. While bond-length restraints were introduced during the initial phases of the disordered refinement to minimize the likelyhood of a divergent refinement, these proved to be unnecessary and were removed during the final cycles of least-squares refinement. Though under this model the two methyl groups of the C(Me)2 moiety may also be expected to be disordered, a model taking this aspect into account failed to yield lower residuals. H atoms were placed in geometrically idealized positions and given a common displacement parameter by class (methyl group H atoms, all others), which were allowed to refine. The final value of Uiso(H) for the methyl group H atoms is 0.141 (4) Å2, and for all other H atoms is 0.095 (3) Å2.

Computing details top

Data collection: XSCANS (Siemens, 1996); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997).

Figures top
[Figure 1] Fig. 1. View of (I) illustrating the numbering scheme (30% probability displacement ellipsoids). The minor fraction of the disordered atoms C71, C81 and C91 have been omitted.
(I) top
Crystal data top
C15H22ODx = 1.077 Mg m3
Mr = 218.33Cu Kα radiation, λ = 1.54178 Å
Orthorhombic, P212121Cell parameters from 99 reflections
a = 6.628 (1) Åθ = 8.0–27.3°
b = 10.218 (1) ŵ = 0.50 mm1
c = 19.889 (1) ÅT = 293 K
V = 1347.0 (3) Å3Block, colorless
Z = 40.4 × 0.4 × 0.3 mm
F(000) = 480
Data collection top
Serial
diffractometer
Rint = 0.041
ω/2θ scansθmax = 67.6°, θmin = 4.5°
Absorption correction: empirical (using intensity measurements)
via ψ scans ((North et al., 1968) using XEMP (Siemens, 1990)
h = 67
Tmin = 0.827, Tmax = 0.866k = 1212
2270 measured reflectionsl = 2323
1911 independent reflections3 standard reflections every 97 reflections
1666 reflections with I > 2σ(I) intensity decay: 1%
Refinement top
Refinement on F2 w = 1/[σ2(Fo2) + (0.0858P)2 + 0.0511P]
where P = (Fo2 + 2Fc2)/3
Least-squares matrix: full(Δ/σ)max = 0.001
R[F2 > 2σ(F2)] = 0.050Δρmax = 0.12 e Å3
wR(F2) = 0.132Δρmin = 0.14 e Å3
S = 1.07Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
1911 reflectionsExtinction coefficient: 0.0052 (12)
176 parametersAbsolute structure: Flack (1983)
0 restraintsAbsolute structure parameter: not reliably determined [0.7 (6)]
H-atom parameters constrained
Crystal data top
C15H22OV = 1347.0 (3) Å3
Mr = 218.33Z = 4
Orthorhombic, P212121Cu Kα radiation
a = 6.628 (1) ŵ = 0.50 mm1
b = 10.218 (1) ÅT = 293 K
c = 19.889 (1) Å0.4 × 0.4 × 0.3 mm
Data collection top
Serial
diffractometer
1666 reflections with I > 2σ(I)
Absorption correction: empirical (using intensity measurements)
via ψ scans ((North et al., 1968) using XEMP (Siemens, 1990)
Rint = 0.041
Tmin = 0.827, Tmax = 0.8663 standard reflections every 97 reflections
2270 measured reflections intensity decay: 1%
1911 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.050H-atom parameters constrained
wR(F2) = 0.132Δρmax = 0.12 e Å3
S = 1.07Δρmin = 0.14 e Å3
1911 reflectionsAbsolute structure: Flack (1983)
176 parametersAbsolute structure parameter: not reliably determined [0.7 (6)]
0 restraints
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
O10.7435 (3)0.5483 (2)0.46305 (11)0.1032 (7)
C10.5760 (3)0.5489 (2)0.43741 (11)0.0706 (6)
C20.4529 (4)0.6664 (2)0.43026 (12)0.0739 (6)
H20.50130.74760.44390.095 (3)*
C30.2689 (4)0.6543 (2)0.40359 (10)0.0685 (6)
C310.1219 (5)0.7633 (3)0.39466 (13)0.0932 (8)
H31A0.01040.75140.42490.141 (4)*
H31B0.07350.76370.34920.141 (4)*
H31C0.18710.84520.40420.141 (4)*
C40.2094 (3)0.5195 (2)0.38143 (10)0.0654 (6)
H40.07660.51160.36020.095 (3)*
C50.3913 (3)0.4655 (2)0.34020 (10)0.0644 (6)
H50.46900.53920.32230.095 (3)*
C60.3674 (4)0.3624 (2)0.28532 (13)0.0837 (7)
C610.2627 (7)0.4305 (4)0.22528 (16)0.1334 (14)
H61A0.25330.37050.18830.141 (4)*
H61B0.34010.50560.21190.141 (4)*
H61C0.12980.45780.23840.141 (4)*
C620.5757 (6)0.3206 (4)0.26353 (18)0.1190 (12)
H62A0.56490.25980.22690.141 (4)*
H62B0.64370.27940.30050.141 (4)*
H62C0.65100.39590.24930.141 (4)*
C710.2145 (19)0.2555 (10)0.2987 (6)0.098 (3)0.565 (14)
H71A0.08000.29190.29450.095 (3)*0.565 (14)
H71B0.22910.18810.26470.095 (3)*0.565 (14)
C810.2355 (19)0.1934 (7)0.3674 (4)0.105 (3)0.565 (14)
H81A0.15650.11360.36900.095 (3)*0.565 (14)
H81B0.37570.17060.37520.095 (3)*0.565 (14)
C910.167 (2)0.2825 (15)0.4200 (8)0.094 (5)0.565 (14)
H91A0.17150.23210.46130.095 (3)*0.565 (14)
H91B0.02550.29820.41080.095 (3)*0.565 (14)
C720.295 (3)0.2293 (16)0.3175 (8)0.106 (4)0.435 (14)
H72A0.27170.16620.28190.095 (3)*0.435 (14)
H72B0.40110.19540.34610.095 (3)*0.435 (14)
C820.1036 (19)0.2432 (10)0.3587 (5)0.096 (4)0.435 (14)
H82A0.03230.16030.35860.095 (3)*0.435 (14)
H82B0.01700.30780.33760.095 (3)*0.435 (14)
C920.146 (3)0.2866 (13)0.4358 (11)0.075 (4)0.435 (14)
H92A0.01860.29410.45960.095 (3)*0.435 (14)
H92B0.22620.22020.45800.095 (3)*0.435 (14)
C100.2574 (3)0.4183 (2)0.43794 (11)0.0682 (6)
C1010.2191 (4)0.4569 (3)0.51137 (11)0.0833 (7)
H10A0.07860.47640.51740.141 (4)*
H10B0.29810.53270.52230.141 (4)*
H10C0.25670.38570.54030.141 (4)*
C110.4774 (3)0.4276 (2)0.41107 (11)0.0665 (6)
H110.55760.34720.41320.095 (3)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0654 (11)0.1316 (16)0.1126 (14)0.0036 (11)0.0180 (10)0.0206 (12)
C10.0560 (12)0.0910 (15)0.0649 (11)0.0036 (11)0.0026 (10)0.0031 (11)
C20.0859 (17)0.0690 (13)0.0668 (12)0.0056 (12)0.0046 (13)0.0065 (10)
C30.0822 (17)0.0703 (12)0.0530 (9)0.0134 (12)0.0073 (12)0.0036 (9)
C310.115 (2)0.0872 (16)0.0778 (14)0.0329 (16)0.0104 (15)0.0097 (13)
C40.0529 (11)0.0794 (13)0.0638 (11)0.0003 (10)0.0059 (10)0.0037 (10)
C50.0616 (12)0.0661 (11)0.0655 (11)0.0043 (11)0.0018 (10)0.0037 (9)
C60.0855 (16)0.0822 (15)0.0833 (15)0.0123 (14)0.0031 (14)0.0230 (12)
C610.165 (4)0.144 (3)0.0909 (19)0.007 (3)0.036 (2)0.037 (2)
C620.120 (3)0.127 (2)0.109 (2)0.008 (2)0.021 (2)0.046 (2)
C710.116 (8)0.077 (4)0.101 (6)0.025 (4)0.025 (5)0.013 (4)
C810.120 (6)0.070 (3)0.125 (6)0.017 (4)0.007 (5)0.013 (3)
C910.067 (5)0.125 (8)0.091 (10)0.014 (4)0.015 (5)0.028 (5)
C720.110 (11)0.103 (9)0.105 (9)0.024 (7)0.000 (6)0.036 (7)
C820.089 (6)0.075 (4)0.123 (7)0.020 (4)0.002 (5)0.014 (4)
C920.099 (9)0.059 (5)0.068 (7)0.015 (4)0.025 (4)0.010 (3)
C100.0576 (12)0.0760 (13)0.0709 (12)0.0017 (11)0.0026 (11)0.0119 (10)
C1010.0750 (14)0.1046 (17)0.0703 (13)0.0082 (15)0.0099 (11)0.0212 (12)
C110.0563 (12)0.0705 (12)0.0727 (12)0.0053 (10)0.0030 (10)0.0022 (9)
Geometric parameters (Å, º) top
O1—C11.222 (3)C6—C711.514 (12)
C1—C21.458 (3)C6—C611.546 (5)
C1—C111.496 (3)C6—C721.579 (17)
C2—C31.336 (4)C71—C811.512 (16)
C3—C311.491 (3)C81—C911.459 (17)
C3—C41.498 (3)C91—C101.553 (15)
C4—C51.559 (3)C72—C821.52 (2)
C4—C101.560 (3)C82—C921.62 (2)
C5—C61.525 (3)C92—C101.537 (15)
C5—C111.569 (3)C10—C1011.534 (3)
C6—C621.509 (5)C10—C111.556 (3)
O1—C1—C2123.6 (2)C5—C6—C72109.6 (5)
O1—C1—C11122.6 (2)C61—C6—C72124.4 (7)
C2—C1—C11113.78 (19)C81—C71—C6113.6 (8)
C3—C2—C1118.2 (2)C91—C81—C71111.0 (10)
C2—C3—C31125.1 (2)C81—C91—C10127.1 (11)
C2—C3—C4116.2 (2)C82—C72—C6113.2 (13)
C31—C3—C4118.7 (2)C72—C82—C92113.1 (12)
C3—C4—C5106.07 (18)C10—C92—C82110.5 (12)
C3—C4—C10110.09 (16)C101—C10—C9299.9 (8)
C5—C4—C1089.24 (16)C101—C10—C91112.6 (6)
C6—C5—C4122.73 (19)C92—C10—C9112.9 (13)
C6—C5—C11120.70 (19)C101—C10—C11117.80 (19)
C4—C5—C1184.03 (15)C92—C10—C11119.7 (8)
C62—C6—C71117.3 (5)C91—C10—C11109.7 (6)
C62—C6—C5107.8 (2)C101—C10—C4118.83 (19)
C71—C6—C5116.2 (5)C92—C10—C4117.5 (8)
C62—C6—C61108.4 (3)C91—C10—C4110.4 (6)
C71—C6—C6199.2 (5)C11—C10—C484.44 (15)
C5—C6—C61106.8 (2)C1—C11—C10109.86 (19)
C62—C6—C7298.7 (7)C1—C11—C5105.62 (18)
C71—C6—C7226.2 (5)C10—C11—C589.02 (15)

Experimental details

Crystal data
Chemical formulaC15H22O
Mr218.33
Crystal system, space groupOrthorhombic, P212121
Temperature (K)293
a, b, c (Å)6.628 (1), 10.218 (1), 19.889 (1)
V3)1347.0 (3)
Z4
Radiation typeCu Kα
µ (mm1)0.50
Crystal size (mm)0.4 × 0.4 × 0.3
Data collection
DiffractometerSerial
diffractometer
Absorption correctionEmpirical (using intensity measurements)
via ψ scans ((North et al., 1968) using XEMP (Siemens, 1990)
Tmin, Tmax0.827, 0.866
No. of measured, independent and
observed [I > 2σ(I)] reflections
2270, 1911, 1666
Rint0.041
(sin θ/λ)max1)0.600
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.050, 0.132, 1.07
No. of reflections1911
No. of parameters176
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.12, 0.14
Absolute structureFlack (1983)
Absolute structure parameternot reliably determined [0.7 (6)]

Computer programs: XSCANS (Siemens, 1996), XSCANS, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEP-3 (Farrugia, 1997).

Selected bond angles (º) top
C5—C4—C1089.24 (16)C11—C10—C484.44 (15)
C4—C5—C1184.03 (15)C10—C11—C589.02 (15)
 

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