Vulgarone B

Acta Cryst.(2001). E57, o99±o101 DOI: 101107/S1600536800020079 Alex F. T. Yokochiet al. C₁₅H₂₂O

o99

organic papers

Acta Crystallographica Section E Structure Reports Online

ISSN 1600-5368

Vulgarone B

Alex F. T. Yokochi,a_{* James D.}

Whitea_{and George Sturtz}b

a_{Department of Chemistry, Oregon State}

University, Corvallis, Oregon, USA, and b_{AromaGen, Albany, Oregon, USA}

Correspondence e-mail: [email protected]

Key indicators

Single-crystal X-ray study T= 293 K

Mean(C±C) = 0.003 AÊ Disorder in main residue Rfactor = 0.050 wRfactor = 0.132

Data-to-parameter ratio = 10.9

For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e.

#2001 International Union of Crystallography Printed in Great Britain ± all rights reserved

The crystal structure of vulgarone B (2,6,6,11-tetramethyltri-cyclo[5.4.0.02,8_{]undec-10-en-9-one), a carbocyclic}

sesquiter-pene 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.

Comment

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 Arte-misia douglasianaBess., 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

Chry-santhemum vulgare (L.) Bernh, [Tanacetum vulgare (L)]

(Uchioet al., 1977). It has also been obtained from the volatile oil of cultivars ofSantolina chamaecyparcissusL. (Baiget al., 1989).

The structure of vulgarone B, including its absolute con®guration, had earlier been deduced from spectroscopic evidence and by chemical correlation with the related sesquiterpene (+)--longipinene (Uchio, 1978). The results from our X-ray single-crystal diffraction experiment con®rm the assigned structure. We also attempted to determine the absolute con®guration of vulgarone B from the diffraction data, but, due to the small magnitude of the anomalous scat-tering components, the re®ned value of the absolute structure parameter could not be reliably determined. This is re¯ected in the fact that the model shown in Fig. 1 yields a value of

ÿ0.7 (6) for this parameter, whereas the inverted model yields a value of 1.7 (6). Further, since the absolute structure derived

organic papers

o100

from the model shown is identical to the previously deduced con®guration for this molecule (Uchio, 1978), we ®nd it reasonable to conclude that this is the true con®guration 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 membered ring. The six-membered ring contains a C CÐC O moiety, which should force ®ve 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) AÊ 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 re¯ected in the CÐCÐC angles within the ring, which are identical pairwise at about 84 and 89_{as shown in Table 1.}

Experimental

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 subli-mation, the crystal was completely encapsulated in a thin layer of epoxy glue. This strategy was suf®cient to allow data collection over a period of a few days.

Crystal data

C15H22O

Mr= 218.33

Orthorhombic,P212121

a= 6.628 (1) AÊ

b= 10.218 (1) AÊ

c= 19.889 (1) AÊ

V= 1347.0 (3) AÊ3

Z= 4

Dx= 1.077 Mg mÿ3

CuKradiation Cell parameters from 99

re¯ections = 8.0±27.3

= 0.50 mmÿ1

T= 293 (2) K Block, colorless 0.40.40.3 mm

Data collection

SiemensP4 diffractometer !/2scans

Absorption correction: empirical

via scans (Northet al., 1968) usingXEMP(Siemens, 1990)

Tmin= 0.827,Tmax= 0.866

2270 measured re¯ections 1911 independent re¯ections 1666 re¯ections withI> 2(I)

Rint= 0.041

max= 67.6

h=ÿ6!7

k=ÿ12!12

l=ÿ23!23 3 standard re¯ections

every 97 re¯ections intensity decay: 1%

Re®nement

Re®nement onF2

R(F) = 0.050

wR(F2_{) = 0.132}

S= 1.07 1911 re¯ections 176 parameters

H-atom parameters constrained

w= 1/[2_(F

o2) + (0.0858P)2

+ 0.0511P]

whereP= (Fo2+ 2Fc2)/3

(/)max= 0.001

max= 0.12 e AÊÿ3

min=ÿ0.14 e AÊÿ3

Extinction correction:SHELXL97 Extinction coef®cient: 0.0052 (12) Absolute structure: Flack (1983) Flack parameter = not reliably

determined [ÿ0.7 (6)]

Table 1

Selected geometric parameters (_). C5ÐC4ÐC10 89.24 (16)

C4ÐC5ÐC11 84.03 (15) C11ÐC10ÐC4C10ÐC11ÐC5 84.44 (15)89.02 (15)

All data was employed in the re®nement with the exception of the (1,1,2) re¯ection which had strongly negative intensity. During the course of the re®nement, the disorder in the C(Me)2(CH2)3backbone

of the seven-membered ring became apparent. This disorder was modelled by introducing two (CH2)3moieties 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 re®ne. While bond-length restraints were introduced during the initial phases of the disordered re®nement to minimize the likelihood of a divergent re®nement, these proved to be unnecessary and were removed during the ®nal cycles of least-squares re®nement. Though under this model the two methyl groups of the C(Me)2moiety 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 re®ne. The ®nal value ofUiso(H) for the methyl group H atoms is 0.141 (4) AÊ2_{, and for all other H atoms is 0.095 (3) AÊ}2_.

Data collection: XSCANS (Siemens, 1996); cell re®nement:

XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to re®ne structure: SHELXL97 (Sheldrick, 1997); molecular graphics:

ORTEP-3 (Farrugia, 1997). Figure 1

The authors wish to acknowledge partial support of this work by the Oregon State University Marine/Freshwater Biomedical Sciences Center through grant No. P30-ES03850.

References

Baig, M. A., Banthorpe, D. V. & Gutowski, J. A. (1989).Fitoterapia,60, 373± 375.

Farrugia, L. J. (1997).J. Appl. Cryst.30, 565. Flack, H. D. (1983).Acta Cryst.A39, 876±881.

North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968).Acta Cryst.A24, 351± 359.

Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of GoÈttingen, Germany.

Siemens (1990).XEMP.Version 4.3. Siemens Analytical X-ray Instruments Inc., Madison, Wisconsin, USA.

Siemens (1996).XSCANS. Version 2.2. Siemens Analytical X-ray Instruments Inc., Madison, Wisconsin, USA.

Uchio, Y. (1978).Tetrahedron,34, 2893±2899.

Uchio, Y., Matsuo, A., Eguchi, S. Nakayama, M. & Hayashi, S. (1977).

Tetrahedron Lett.pp. 1191±1194.

White, J. D. & Lee, N. C. (1997).Advances in Organic Chemistry, Vol. 6, edited by B. Halton, pp. 1±34. Hampton Hill, England: Jai Press.

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Acta Cryst. (2001). E57, o99–o101 [doi:10.1107/S1600536800020079]

Vulgarone B

Alex F. T. Yokochi, James D. White and George Sturtz

S1. Comment

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 C═C\sb C═O 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.

S2. Experimental

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

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S3. Refinement

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_.

Figure 1

View of (I) illustrating the numbering scheme (30% probability displacement ellipsoids). The minor fraction of the

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(I)

Crystal data

C15H22O

Mr = 218.33

Orthorhombic, P212121

a = 6.628 (1) Å

b = 10.218 (1) Å

c = 19.889 (1) Å

V = 1347.0 (3) Å3

Z = 4

F(000) = 480

Dx = 1.077 Mg m−3

Cu Kα radiation, λ = 1.54178 Å Cell parameters from 99 reflections

θ = 8.0–27.3°

µ = 0.50 mm−1

T = 293 K Block, colorless 0.4 × 0.4 × 0.3 mm

Data collection

Serial

diffractometer

ω/2θ scans

Absorption correction: empirical (using intensity measurements)

via ψ scans ((North et al., 1968) using XEMP

(Siemens, 1990)

Tmin = 0.827, Tmax = 0.866

2270 measured reflections

1911 independent reflections 1666 reflections with I > 2σ(I)

Rint = 0.041

θmax = 67.6°, θmin = 4.5°

h = −6→7

k = −12→12

l = −23→23

3 standard reflections every 97 reflections intensity decay: 1%

Refinement

Refinement on F2

Least-squares matrix: full

R[F2 _{> 2σ(F}2_{)] = 0.050}

wR(F2_{) = 0.132}

S = 1.07 1911 reflections 176 parameters 0 restraints

H-atom parameters constrained

w = 1/[σ2_(F

o2) + (0.0858P)2 + 0.0511P]

where P = (Fo2 + 2Fc2)/3

(Δ/σ)max = 0.001

Δρmax = 0.12 e Å−3

Δρmin = −0.14 e Å−3

Extinction correction: SHELXL97, Fc*_{=kFc[1+0.001xFc}2_λ3_/sin(2θ)]-1/4

Extinction coefficient: 0.0052 (12) Absolute structure: Flack (1983)

Absolute structure parameter: not reliably determined [−0.7 (6)]

Special details

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₎

x y z Uiso*/Ueq Occ. (<1)

O1 0.7435 (3) 0.5483 (2) 0.46305 (11) 0.1032 (7)

C1 0.5760 (3) 0.5489 (2) 0.43741 (11) 0.0706 (6)

C2 0.4529 (4) 0.6664 (2) 0.43026 (12) 0.0739 (6)

H2 0.5013 0.7476 0.4439 0.095 (3)*

C3 0.2689 (4) 0.6543 (2) 0.40359 (10) 0.0685 (6)

C31 0.1219 (5) 0.7633 (3) 0.39466 (13) 0.0932 (8)

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H31B 0.0735 0.7637 0.3492 0.141 (4)*

H31C 0.1871 0.8452 0.4042 0.141 (4)*

C4 0.2094 (3) 0.5195 (2) 0.38143 (10) 0.0654 (6)

H4 0.0766 0.5116 0.3602 0.095 (3)*

C5 0.3913 (3) 0.4655 (2) 0.34020 (10) 0.0644 (6)

H5 0.4690 0.5392 0.3223 0.095 (3)*

C6 0.3674 (4) 0.3624 (2) 0.28532 (13) 0.0837 (7)

C61 0.2627 (7) 0.4305 (4) 0.22528 (16) 0.1334 (14)

H61A 0.2533 0.3705 0.1883 0.141 (4)*

H61B 0.3401 0.5056 0.2119 0.141 (4)*

H61C 0.1298 0.4578 0.2384 0.141 (4)*

C62 0.5757 (6) 0.3206 (4) 0.26353 (18) 0.1190 (12)

H62A 0.5649 0.2598 0.2269 0.141 (4)*

H62B 0.6437 0.2794 0.3005 0.141 (4)*

H62C 0.6510 0.3959 0.2493 0.141 (4)*

C71 0.2145 (19) 0.2555 (10) 0.2987 (6) 0.098 (3) 0.565 (14)

H71A 0.0800 0.2919 0.2945 0.095 (3)* 0.565 (14)

H71B 0.2291 0.1881 0.2647 0.095 (3)* 0.565 (14)

C81 0.2355 (19) 0.1934 (7) 0.3674 (4) 0.105 (3) 0.565 (14)

H81A 0.1565 0.1136 0.3690 0.095 (3)* 0.565 (14)

H81B 0.3757 0.1706 0.3752 0.095 (3)* 0.565 (14)

C91 0.167 (2) 0.2825 (15) 0.4200 (8) 0.094 (5) 0.565 (14)

H91A 0.1715 0.2321 0.4613 0.095 (3)* 0.565 (14)

H91B 0.0255 0.2982 0.4108 0.095 (3)* 0.565 (14)

C72 0.295 (3) 0.2293 (16) 0.3175 (8) 0.106 (4) 0.435 (14)

H72A 0.2717 0.1662 0.2819 0.095 (3)* 0.435 (14)

H72B 0.4011 0.1954 0.3461 0.095 (3)* 0.435 (14)

C82 0.1036 (19) 0.2432 (10) 0.3587 (5) 0.096 (4) 0.435 (14)

H82A 0.0323 0.1603 0.3586 0.095 (3)* 0.435 (14)

H82B 0.0170 0.3078 0.3376 0.095 (3)* 0.435 (14)

C92 0.146 (3) 0.2866 (13) 0.4358 (11) 0.075 (4) 0.435 (14)

H92A 0.0186 0.2941 0.4596 0.095 (3)* 0.435 (14)

H92B 0.2262 0.2202 0.4580 0.095 (3)* 0.435 (14)

C10 0.2574 (3) 0.4183 (2) 0.43794 (11) 0.0682 (6)

C101 0.2191 (4) 0.4569 (3) 0.51137 (11) 0.0833 (7)

H10A 0.0786 0.4764 0.5174 0.141 (4)*

H10B 0.2981 0.5327 0.5223 0.141 (4)*

H10C 0.2567 0.3857 0.5403 0.141 (4)*

C11 0.4774 (3) 0.4276 (2) 0.41107 (11) 0.0665 (6)

H11 0.5576 0.3472 0.4132 0.095 (3)*

Atomic displacement parameters (Å2₎

U11 _U22 _U33 _U12 _U13 _U23

O1 0.0654 (11) 0.1316 (16) 0.1126 (14) −0.0036 (11) −0.0180 (10) −0.0206 (12)

C1 0.0560 (12) 0.0910 (15) 0.0649 (11) −0.0036 (11) −0.0026 (10) −0.0031 (11)

C2 0.0859 (17) 0.0690 (13) 0.0668 (12) −0.0056 (12) −0.0046 (13) −0.0065 (10)

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C31 0.115 (2) 0.0872 (16) 0.0778 (14) 0.0329 (16) 0.0104 (15) 0.0097 (13)

C4 0.0529 (11) 0.0794 (13) 0.0638 (11) −0.0003 (10) −0.0059 (10) 0.0037 (10)

C5 0.0616 (12) 0.0661 (11) 0.0655 (11) −0.0043 (11) −0.0018 (10) −0.0037 (9)

C6 0.0855 (16) 0.0822 (15) 0.0833 (15) −0.0123 (14) 0.0031 (14) −0.0230 (12)

C61 0.165 (4) 0.144 (3) 0.0909 (19) −0.007 (3) −0.036 (2) −0.037 (2)

C62 0.120 (3) 0.127 (2) 0.109 (2) 0.008 (2) 0.021 (2) −0.046 (2)

C71 0.116 (8) 0.077 (4) 0.101 (6) −0.025 (4) −0.025 (5) −0.013 (4)

C81 0.120 (6) 0.070 (3) 0.125 (6) −0.017 (4) −0.007 (5) 0.013 (3)

C91 0.067 (5) 0.125 (8) 0.091 (10) −0.014 (4) 0.015 (5) 0.028 (5)

C72 0.110 (11) 0.103 (9) 0.105 (9) −0.024 (7) 0.000 (6) −0.036 (7)

C82 0.089 (6) 0.075 (4) 0.123 (7) −0.020 (4) 0.002 (5) −0.014 (4)

C92 0.099 (9) 0.059 (5) 0.068 (7) −0.015 (4) 0.025 (4) 0.010 (3)

C10 0.0576 (12) 0.0760 (13) 0.0709 (12) 0.0017 (11) 0.0026 (11) 0.0119 (10)

C101 0.0750 (14) 0.1046 (17) 0.0703 (13) 0.0082 (15) 0.0099 (11) 0.0212 (12)

C11 0.0563 (12) 0.0705 (12) 0.0727 (12) 0.0053 (10) −0.0030 (10) 0.0022 (9)

Geometric parameters (Å, º)

O1—C1 1.222 (3) C6—C71 1.514 (12)

C1—C2 1.458 (3) C6—C61 1.546 (5)

C1—C11 1.496 (3) C6—C72 1.579 (17)

C2—C3 1.336 (4) C71—C81 1.512 (16)

C3—C31 1.491 (3) C81—C91 1.459 (17)

C3—C4 1.498 (3) C91—C10 1.553 (15)

C4—C5 1.559 (3) C72—C82 1.52 (2)

C4—C10 1.560 (3) C82—C92 1.62 (2)

C5—C6 1.525 (3) C92—C10 1.537 (15)

C5—C11 1.569 (3) C10—C101 1.534 (3)

C6—C62 1.509 (5) C10—C11 1.556 (3)

O1—C1—C2 123.6 (2) C5—C6—C72 109.6 (5)

O1—C1—C11 122.6 (2) C61—C6—C72 124.4 (7)

C2—C1—C11 113.78 (19) C81—C71—C6 113.6 (8)

C3—C2—C1 118.2 (2) C91—C81—C71 111.0 (10)

C2—C3—C31 125.1 (2) C81—C91—C10 127.1 (11)

C2—C3—C4 116.2 (2) C82—C72—C6 113.2 (13)

C31—C3—C4 118.7 (2) C72—C82—C92 113.1 (12)

C3—C4—C5 106.07 (18) C10—C92—C82 110.5 (12)

C3—C4—C10 110.09 (16) C101—C10—C92 99.9 (8)

C5—C4—C10 89.24 (16) C101—C10—C91 112.6 (6)

C6—C5—C4 122.73 (19) C92—C10—C91 12.9 (13)

C6—C5—C11 120.70 (19) C101—C10—C11 117.80 (19)

C4—C5—C11 84.03 (15) C92—C10—C11 119.7 (8)

C62—C6—C71 117.3 (5) C91—C10—C11 109.7 (6)

C62—C6—C5 107.8 (2) C101—C10—C4 118.83 (19)

C71—C6—C5 116.2 (5) C92—C10—C4 117.5 (8)

C62—C6—C61 108.4 (3) C91—C10—C4 110.4 (6)

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C5—C6—C61 106.8 (2) C1—C11—C10 109.86 (19)

C62—C6—C72 98.7 (7) C1—C11—C5 105.62 (18)