Dehydro-leucodin: a guaiane-type sesquiterpene lactone.

Dehydro-leucodin [systematic name: (1S,6S,2R)-9,13-dimeth-yl-5-methyl-ene-3-oxatricyclo-[8.3.0.0(2,6)]trideca-9,12-diene-4,11-dione], C(15)H(16)O(3), is a guanolide isolated from Artemisia douglasiana. The fused-ring system contains a seven-membered ring that adopts a chair conformation, a fused planar cyclo-pentenone ring and a five-membered lactone ring fused in envelope conformation. The absolute structure determined by X-ray analysis agrees with that previously assigned to this compound by NMR studies [Bohlmann & Zdero (1972 ▶). Tetra-hedron Lett.13, 621-624] and also with that of leucodine, a closely related guaianolide [Martinez et al. (1988 ▶). J. Nat. Prod.51, 221-228].

Related literature

For NMR studies of dehydro­leucodin and leucodine, see: Bohlmann & Zdero (1972 ▶); Martinez et al., (1988 ▶). For the pharmacological activity of dehydro­leucodin and related compounds, see Giordano et al. (1992 ▶).

Experimental

Crystal data

C15H16O3

M = 244.28

Orthorhombic,

a = 7.5101 (3) Å

b = 11.1065 (4) Å

c = 15.0228 (6) Å

V = 1253.07 (8) Å3

Z = 4

Cu Kα radiation

μ = 0.73 mm−1

T = 100 K

0.29 × 0.07 × 0.05 mm

Data collection

Bruker APEXII DUO diffractometer

Absorption correction: integration (SADABS; Bruker, 2008 ▶) T min = 0.820, T max = 0.962

10896 measured reflections

2166 independent reflections

2150 reflections with I > 2σ(I)

R int = 0.064

Refinement

R[F 2 > 2σ(F 2)] = 0.027

wR(F 2) = 0.068

S = 1.05

2166 reflections

165 parameters

H-atom parameters constrained

Δρmax = 0.19 e Å−3

Δρmin = −0.14 e Å−3

Absolute structure: Flack (1983 ▶), 879 Friedel pairs

Flack parameter: 0.00 (17)

Data collection: APEX2 (Bruker, 2008 ▶); cell refinement: SAINT (Bruker, 2008 ▶); 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.

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811048938/bg2432sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811048938/bg2432Isup2.hkl

Supplementary material file. DOI: 10.1107/S1600536811048938/bg2432Isup3.mol

Supplementary material file. DOI: 10.1107/S1600536811048938/bg2432Isup4.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

C15H16O3	Dehydroleucodin
Mr = 244.28	Dx = 1.295 Mg m−3
Orthorhombic, P212121	Cu Kα radiation, λ = 1.54178 Å
Hall symbol: P 2ac 2ab	Cell parameters from 9973 reflections
a = 7.5101 (3) Å	θ = 2.9–67.8°
b = 11.1065 (4) Å	µ = 0.73 mm−1
c = 15.0228 (6) Å	T = 100 K
V = 1253.07 (8) Å3	Needles, colourless
Z = 4	0.29 × 0.07 × 0.05 mm
F(000) = 520

Bruker APEXII DUO diffractometer	2166 independent reflections
Radiation source: IµS microsource	2150 reflections with I > 2σ(I)
graphite	Rint = 0.064
phi and ω scans	θmax = 66.4°, θmin = 5.0°
Absorption correction: integration (SADABS; Bruker, 2008)	h = −8→7
Tmin = 0.820, Tmax = 0.962	k = −13→12
10896 measured reflections	l = −17→17

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)] = 0.027	H-atom parameters constrained
wR(F2) = 0.068	w = 1/[σ2(Fo2) + (0.0273P)2 + 0.2735P] where P = (Fo2 + 2Fc2)/3
S = 1.05	(Δ/σ)max < 0.001
2166 reflections	Δρmax = 0.19 e Å−3
165 parameters	Δρmin = −0.14 e Å−3
0 restraints	Absolute structure: Flack (1983), 879 Friedel pairs
Primary atom site location: structure-invariant direct methods	Flack parameter: 0.00 (17)

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. All H atoms were positioned geometrically (C—H=0.93/1.00 Å) and allowed to ride with Uiso(H)=1.2/1.5Ueq(C). Methyl ones were allowed to rotate around the corresponding C—C. The Flack x parameter is 0.00 (17) confirming that the correct enantiomer is refined for this structure.

	x	y	z	Uiso*/Ueq
O1	0.81504 (13)	−0.02962 (8)	0.26751 (7)	0.0312 (2)
O2	0.80476 (13)	0.43297 (8)	0.09948 (6)	0.0248 (2)
O3	0.87294 (16)	0.62331 (10)	0.06281 (7)	0.0411 (3)
C1	0.68912 (15)	0.17287 (10)	0.25112 (8)	0.0192 (3)
C2	0.77553 (16)	0.05869 (11)	0.22172 (10)	0.0240 (3)
C3	0.79958 (18)	0.06797 (12)	0.12543 (10)	0.0278 (3)
H3A	0.8526	0.0072	0.0897	0.033*
C4	0.73794 (16)	0.17220 (12)	0.09389 (9)	0.0241 (3)
C5	0.66907 (16)	0.25183 (10)	0.16885 (8)	0.0192 (3)
H5A	0.5406	0.2712	0.1588	0.023*
C6	0.77492 (16)	0.36796 (10)	0.18300 (8)	0.0183 (3)
H6A	0.8926	0.3478	0.2104	0.022*
C7	0.68007 (16)	0.46068 (10)	0.24137 (8)	0.0190 (3)
H7A	0.5548	0.4662	0.2191	0.023*
C8	0.66895 (18)	0.43149 (11)	0.33978 (8)	0.0227 (3)
H8A	0.6197	0.5015	0.3723	0.027*
H8B	0.7899	0.4154	0.3631	0.027*
C9	0.55009 (17)	0.32097 (11)	0.35585 (8)	0.0224 (3)
H9A	0.5127	0.3202	0.4190	0.027*
H9B	0.4414	0.3286	0.3190	0.027*
C10	0.63981 (17)	0.20247 (11)	0.33441 (9)	0.0209 (3)
C11	0.77282 (17)	0.57383 (11)	0.21226 (9)	0.0215 (3)
C12	0.82427 (19)	0.55285 (12)	0.11838 (9)	0.0269 (3)
C13	0.80965 (17)	0.67457 (11)	0.25533 (10)	0.0266 (3)
H13A	0.8719	0.7376	0.2260	0.032*
H13B	0.7739	0.6839	0.3156	0.032*
C14	0.7232 (2)	0.20714 (14)	−0.00173 (9)	0.0321 (3)
H14A	0.7834	0.1469	−0.0387	0.048*
H14B	0.7792	0.2859	−0.0107	0.048*
H14C	0.5973	0.2116	−0.0186	0.048*
C15	0.6668 (2)	0.12277 (12)	0.41396 (9)	0.0304 (3)
H15A	0.5508	0.0977	0.4374	0.046*
H15B	0.7319	0.1671	0.4600	0.046*
H15C	0.7353	0.0515	0.3964	0.046*

	U11	U22	U33	U12	U13	U23
O1	0.0261 (5)	0.0160 (4)	0.0516 (6)	0.0001 (4)	−0.0029 (4)	0.0034 (4)
O2	0.0299 (5)	0.0231 (4)	0.0214 (4)	−0.0035 (4)	0.0023 (4)	0.0021 (4)
O3	0.0564 (7)	0.0322 (6)	0.0347 (6)	−0.0113 (5)	0.0045 (5)	0.0112 (5)
C1	0.0158 (6)	0.0158 (5)	0.0261 (6)	−0.0017 (5)	−0.0029 (5)	0.0001 (5)
C2	0.0158 (6)	0.0161 (6)	0.0401 (8)	−0.0039 (5)	−0.0027 (5)	−0.0029 (5)
C3	0.0244 (7)	0.0213 (6)	0.0377 (8)	−0.0010 (6)	0.0033 (6)	−0.0118 (6)
C4	0.0191 (6)	0.0257 (6)	0.0275 (7)	−0.0051 (5)	0.0011 (5)	−0.0076 (6)
C5	0.0169 (6)	0.0182 (6)	0.0225 (6)	−0.0011 (5)	−0.0013 (5)	−0.0027 (5)
C6	0.0186 (6)	0.0176 (6)	0.0186 (6)	−0.0002 (5)	−0.0010 (5)	0.0015 (5)
C7	0.0179 (6)	0.0156 (5)	0.0236 (6)	0.0019 (5)	−0.0008 (5)	−0.0001 (5)
C8	0.0275 (7)	0.0179 (6)	0.0227 (7)	0.0003 (5)	−0.0003 (5)	−0.0032 (5)
C9	0.0259 (6)	0.0215 (6)	0.0198 (6)	−0.0015 (6)	0.0017 (5)	−0.0022 (5)
C10	0.0193 (6)	0.0181 (6)	0.0253 (6)	−0.0041 (5)	−0.0037 (5)	0.0014 (5)
C11	0.0176 (6)	0.0179 (6)	0.0289 (7)	0.0018 (5)	−0.0032 (5)	0.0037 (5)
C12	0.0277 (7)	0.0223 (6)	0.0305 (7)	−0.0047 (6)	−0.0033 (6)	0.0050 (5)
C13	0.0219 (6)	0.0190 (6)	0.0389 (7)	0.0007 (5)	−0.0039 (6)	0.0003 (6)
C14	0.0315 (8)	0.0399 (8)	0.0251 (7)	−0.0044 (6)	0.0018 (6)	−0.0099 (6)
C15	0.0371 (8)	0.0252 (6)	0.0288 (7)	−0.0026 (6)	−0.0048 (6)	0.0075 (6)

O1—C2	1.2343 (17)	C7—H7A	1.0000
O2—C12	1.3692 (16)	C8—C9	1.5369 (17)
O2—C6	1.4649 (14)	C8—H8A	0.9900
O3—C12	1.2012 (17)	C8—H8B	0.9900
C1—C10	1.3456 (19)	C9—C10	1.5132 (17)
C1—C2	1.4914 (16)	C9—H9A	0.9900
C1—C5	1.5230 (17)	C9—H9B	0.9900
C2—C3	1.461 (2)	C10—C15	1.5009 (18)
C3—C4	1.334 (2)	C11—C13	1.3218 (18)
C3—H3A	0.9500	C11—C12	1.4808 (19)
C4—C14	1.4920 (19)	C13—H13A	0.9500
C4—C5	1.5225 (17)	C13—H13B	0.9500
C5—C6	1.5299 (16)	C14—H14A	0.9800
C5—H5A	1.0000	C14—H14B	0.9800
C6—C7	1.5286 (17)	C14—H14C	0.9800
C6—H6A	1.0000	C15—H15A	0.9800
C7—C11	1.5019 (16)	C15—H15B	0.9800
C7—C8	1.5158 (17)	C15—H15C	0.9800
C12—O2—C6	108.55 (9)	C7—C8—H8B	109.5
C10—C1—C2	127.08 (12)	C9—C8—H8B	109.5
C10—C1—C5	125.92 (11)	H8A—C8—H8B	108.1
C2—C1—C5	107.0 (1)	C10—C9—C8	113.74 (10)
O1—C2—C3	125.31 (13)	C10—C9—H9A	108.8
O1—C2—C1	127.97 (13)	C8—C9—H9A	108.8
C3—C2—C1	106.68 (11)	C10—C9—H9B	108.8
C4—C3—C2	111.72 (12)	C8—C9—H9B	108.8
C4—C3—H3A	124.1	H9A—C9—H9B	107.7
C2—C3—H3A	124.1	C1—C10—C15	123.99 (12)
C3—C4—C14	126.41 (12)	C1—C10—C9	122.21 (11)
C3—C4—C5	111.05 (12)	C15—C10—C9	113.80 (11)
C14—C4—C5	122.40 (12)	C13—C11—C12	123.01 (12)
C4—C5—C1	103.43 (10)	C13—C11—C7	131.52 (13)
C4—C5—C6	114.58 (10)	C12—C11—C7	105.47 (10)
C1—C5—C6	108.75 (9)	O3—C12—O2	121.46 (13)
C4—C5—H5A	110.0	O3—C12—C11	129.70 (13)
C1—C5—H5A	110.0	O2—C12—C11	108.82 (11)
C6—C5—H5A	110.0	C11—C13—H13A	120.0
O2—C6—C7	103.33 (9)	C11—C13—H13B	120.0
O2—C6—C5	112.09 (9)	H13A—C13—H13B	120.0
C7—C6—C5	113.92 (10)	C4—C14—H14A	109.5
O2—C6—H6A	109.1	C4—C14—H14B	109.5
C7—C6—H6A	109.1	H14A—C14—H14B	109.5
C5—C6—H6A	109.1	C4—C14—H14C	109.5
C11—C7—C8	119.24 (11)	H14A—C14—H14C	109.5
C11—C7—C6	100.4 (1)	H14B—C14—H14C	109.5
C8—C7—C6	116.17 (10)	C10—C15—H15A	109.5
C11—C7—H7A	106.7	C10—C15—H15B	109.5
C8—C7—H7A	106.7	H15A—C15—H15B	109.5
C6—C7—H7A	106.7	C10—C15—H15C	109.5
C7—C8—C9	110.86 (10)	H15A—C15—H15C	109.5
C7—C8—H8A	109.5	H15B—C15—H15C	109.5
C9—C8—H8A	109.5