(-)-istanbulin a.

THE TITLE COMPOUND (SYSTEMATIC NAME: 9a-hydr-oxy-3,4a,5-trimethyl-4a,6,7,8a,9,9a-hexa-hydro-4H,5H-naphtho[2,3-b]furan-2,8-dione), C(15)H(20)O(4), is a sesquiterpene lactone showing the typical eremophilanolide skeleton, which has been isolated from the plant Senecio candidans collected in the Chilean Magallanes region. The present study confirms the atomic connectivity assigned on the basis of (1)H and (13)C NMR spectroscopy, as well as the relative stereochemistry of the 4α-methyl,5α-methyl,8β-hydr-oxy,10β-H unit. The crystal structure is stabilized by inter-molecular O-H⋯O hydrogen bonds involving the hydr-oxy group as donor and the oxo group as acceptor, giving chains along the a axis. The absolute structure was not determined because of the lack of suitable anomalous scatters.

Related literature

For the biological activity of metabolites isolated from plants of the Senecio species, see: Ulubelen et al. (1971 ▶); Burgueño-Tapia et al. (2007 ▶); Domínguez et al. (2008 ▶); Reina,González-Coloma, Domínguez-Díaz et al. (2006 ▶); Reina, González-Coloma, Gutiérrez et al. (2006 ▶).

Experimental

Crystal data

C15H20O4

M = 264.31

Monoclinic,

a = 7.432 (4) Å

b = 13.010 (6) Å

c = 8.161 (6) Å

β = 115.47 (4)°

V = 712.4 (8) Å3

Z = 2

Mo Kα radiation

μ = 0.09 mm−1

T = 293 K

0.45 × 0.35 × 0.25 mm

Data collection

Enraf–Nonius KappaCCD diffractometer

Absorption correction: none

4410 measured reflections

1678 independent reflections

1485 reflections with I > 2σ(I)

R int = 0.018

Refinement

R[F 2 > 2σ(F 2)] = 0.038

wR(F 2) = 0.095

S = 1.04

1678 reflections

186 parameters

1 restraint

H atoms treated by a mixture of independent and constrained refinement

Δρmax = 0.20 e Å−3

Δρmin = −0.12 e Å−3

Data collection: COLLECT (Nonius, 2000 ▶); cell refinement: SCALEPACK (Otwinowski & Minor, 1997 ▶); data reduction: SCALEPACK and DENZO (Otwinowski & Minor, 1997 ▶); program(s) used to solve structure: SIR97 (Altomare et al., 1999 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶ ); molecular graphics: PLATON (Spek, 2009 ▶); software used to prepare material for publication: Win GX (Farrugia,1999 ▶).

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809033418/hg2542sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809033418/hg2542Isup2.hkl

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

C15H20O4	F(000) = 284
Mr = 264.31	Dx = 1.232 Mg m−3
Monoclinic, P21	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2yb	Cell parameters from 297 reflections
a = 7.432 (4) Å	θ = 4.3–23.7°
b = 13.010 (6) Å	µ = 0.09 mm−1
c = 8.161 (6) Å	T = 293 K
β = 115.47 (4)°	Block, colourless
V = 712.4 (8) Å3	0.45 × 0.35 × 0.25 mm
Z = 2

Enraf–Nonius KappaCCD diffractometer	1485 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.018
graphite	θmax = 27.5°, θmin = 6.4°
Detector resolution: 9 pixels mm-1	h = −9→9
φ and ω scans	k = −16→15
4410 measured reflections	l = −10→10
1678 independent reflections

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.038	Hydrogen site location: difference Fourier map
wR(F2) = 0.095	H atoms treated by a mixture of independent and constrained refinement
S = 1.04	w = 1/[σ2(Fo2) + (0.0482P)2 + 0.0898P] where P = (Fo2 + 2Fc2)/3
1678 reflections	(Δ/σ)max = 0.001
186 parameters	Δρmax = 0.20 e Å−3
1 restraint	Δρmin = −0.11 e Å−3

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
O1	0.4955 (3)	0.50383 (14)	0.8319 (2)	0.0568 (5)
O2	0.5421 (4)	0.5731 (2)	0.6018 (3)	0.0869 (7)
O3	0.6082 (2)	0.37119 (15)	1.04064 (19)	0.0521 (4)
H3	0.713 (5)	0.354 (3)	1.018 (4)	0.079 (9)*
O4	−0.0560 (2)	0.35876 (16)	0.9801 (3)	0.0635 (5)
C1	0.0324 (3)	0.28290 (19)	0.9675 (3)	0.0456 (5)
C2	−0.0216 (4)	0.1763 (2)	0.9971 (4)	0.0635 (7)
H2A	−0.1422	0.1778	1.0153	0.079 (9)*
H2B	0.0844	0.1476	1.1053	0.073 (9)*
C3	−0.0542 (4)	0.1087 (2)	0.8333 (4)	0.0643 (7)
H3A	−0.1759	0.1299	0.7312	0.074 (9)*
H3B	−0.0713	0.0379	0.8615	0.059 (8)*
C4	0.1189 (4)	0.11441 (18)	0.7792 (3)	0.0518 (6)
H4	0.2377	0.0891	0.8827	0.059 (7)*
C5	0.1632 (3)	0.22659 (16)	0.7435 (3)	0.0375 (4)
C6	0.3567 (3)	0.22904 (18)	0.7137 (3)	0.0448 (5)
H6A	0.4602	0.1896	0.8084	0.057 (7)*
H6B	0.3309	0.1977	0.5979	0.050 (7)*
C7	0.4259 (3)	0.33673 (18)	0.7168 (3)	0.0422 (5)
C8	0.4541 (3)	0.40177 (17)	0.8797 (3)	0.0412 (5)
C9	0.2648 (3)	0.40183 (17)	0.9078 (3)	0.0407 (5)
H9A	0.1589	0.4368	0.8076	0.036 (5)*
H9B	0.2875	0.4377	1.0192	0.043 (6)*
C10	0.2059 (3)	0.29068 (16)	0.9181 (3)	0.0372 (4)
H10	0.3200	0.2583	1.0170	0.044 (6)*
C11	0.4554 (3)	0.3931 (2)	0.5961 (3)	0.0488 (6)
C12	0.5040 (4)	0.4988 (3)	0.6676 (4)	0.0588 (6)
C13	0.4395 (4)	0.3664 (3)	0.4119 (3)	0.0668 (8)
H13A	0.5521	0.3940	0.3982	0.090*
H13B	0.3190	0.3950	0.3207	0.090*
H13C	0.4374	0.2930	0.3988	0.090*
C14	−0.0102 (3)	0.27228 (19)	0.5782 (3)	0.0512 (5)
H14A	0.0173	0.3431	0.5648	0.090*
H14B	−0.1303	0.2676	0.5947	0.090*
H14C	−0.0266	0.2348	0.4713	0.090*
C15	0.0800 (5)	0.0415 (2)	0.6210 (5)	0.0771 (9)
H15A	0.1886	0.0454	0.5872	0.090*
H15B	−0.0415	0.0607	0.5195	0.090*
H15C	0.0685	−0.0276	0.6569	0.090*

	U11	U22	U33	U12	U13	U23
O1	0.0612 (10)	0.0542 (10)	0.0633 (10)	−0.0224 (8)	0.0348 (8)	−0.0122 (8)
O2	0.0968 (16)	0.0837 (16)	0.0944 (16)	−0.0249 (13)	0.0548 (14)	0.0156 (13)
O3	0.0339 (7)	0.0817 (12)	0.0434 (7)	−0.0078 (8)	0.0194 (6)	−0.0091 (8)
O4	0.0465 (9)	0.0680 (12)	0.0928 (12)	−0.0034 (9)	0.0460 (9)	−0.0125 (10)
C1	0.0355 (10)	0.0562 (14)	0.0480 (11)	−0.0048 (10)	0.0208 (9)	−0.0015 (11)
C2	0.0559 (14)	0.0680 (18)	0.0766 (17)	−0.0052 (13)	0.0378 (13)	0.0159 (15)
C3	0.0604 (15)	0.0452 (14)	0.0848 (18)	−0.0128 (12)	0.0289 (14)	0.0092 (14)
C4	0.0517 (12)	0.0354 (11)	0.0592 (13)	0.0019 (10)	0.0153 (11)	0.0043 (11)
C5	0.0343 (9)	0.0339 (10)	0.0398 (9)	0.0004 (8)	0.0118 (8)	−0.0005 (9)
C6	0.0463 (11)	0.0476 (12)	0.0440 (10)	0.0054 (10)	0.0228 (9)	−0.0063 (10)
C7	0.0325 (9)	0.0558 (13)	0.0408 (10)	−0.0020 (9)	0.0183 (8)	−0.0071 (10)
C8	0.0384 (10)	0.0472 (12)	0.0423 (10)	−0.0099 (9)	0.0213 (8)	−0.0077 (9)
C9	0.0367 (9)	0.0430 (12)	0.0488 (11)	−0.0050 (8)	0.0244 (9)	−0.0109 (9)
C10	0.0282 (8)	0.0438 (11)	0.0407 (10)	0.0015 (8)	0.0161 (7)	0.0002 (9)
C11	0.0378 (10)	0.0703 (16)	0.0414 (10)	−0.0015 (10)	0.0201 (8)	0.0010 (11)
C12	0.0495 (13)	0.0745 (18)	0.0584 (13)	−0.0133 (12)	0.0290 (11)	0.0039 (13)
C13	0.0641 (14)	0.099 (2)	0.0423 (11)	−0.0002 (16)	0.0278 (11)	0.0043 (14)
C14	0.0465 (12)	0.0464 (13)	0.0465 (11)	0.0016 (10)	0.0066 (9)	0.0057 (11)
C15	0.089 (2)	0.0412 (14)	0.093 (2)	−0.0098 (14)	0.0316 (18)	−0.0157 (14)

O1—C12	1.371 (3)	C6—H6A	0.9700
O1—C8	1.454 (3)	C6—H6B	0.9700
O2—C12	1.198 (4)	C7—C11	1.320 (3)
O3—C8	1.379 (3)	C7—C8	1.512 (3)
O3—H3	0.90 (4)	C8—C9	1.519 (3)
O4—C1	1.214 (3)	C9—C10	1.524 (3)
C1—C2	1.493 (4)	C9—H9A	0.9700
C1—C10	1.511 (3)	C9—H9B	0.9700
C2—C3	1.530 (4)	C10—H10	0.9800
C2—H2A	0.9700	C11—C12	1.477 (4)
C2—H2B	0.9700	C11—C13	1.497 (3)
C3—C4	1.532 (4)	C13—H13A	0.9600
C3—H3A	0.9700	C13—H13B	0.9600
C3—H3B	0.9700	C13—H13C	0.9600
C4—C15	1.526 (4)	C14—H14A	0.9600
C4—C5	1.551 (3)	C14—H14B	0.9600
C4—H4	0.9800	C14—H14C	0.9600
C5—C14	1.529 (3)	C15—H15A	0.9600
C5—C6	1.558 (3)	C15—H15B	0.9600
C5—C10	1.561 (3)	C15—H15C	0.9600
C6—C7	1.489 (3)
C12—O1—C8	108.86 (19)	O1—C8—C7	103.91 (17)
C8—O3—H3	108 (2)	O3—C8—C9	107.47 (17)
O4—C1—C2	123.30 (19)	O1—C8—C9	110.88 (18)
O4—C1—C10	121.5 (2)	C7—C8—C9	110.20 (16)
C2—C1—C10	115.2 (2)	C8—C9—C10	108.33 (16)
C1—C2—C3	110.2 (2)	C8—C9—H9A	110.0
C1—C2—H2A	109.6	C10—C9—H9A	110.0
C3—C2—H2A	109.6	C8—C9—H9B	110.0
C1—C2—H2B	109.6	C10—C9—H9B	110.0
C3—C2—H2B	109.6	H9A—C9—H9B	108.4
H2A—C2—H2B	108.1	C1—C10—C9	112.13 (17)
C2—C3—C4	112.8 (2)	C1—C10—C5	110.24 (17)
C2—C3—H3A	109.0	C9—C10—C5	114.02 (16)
C4—C3—H3A	109.0	C1—C10—H10	106.7
C2—C3—H3B	109.0	C9—C10—H10	106.7
C4—C3—H3B	109.0	C5—C10—H10	106.7
H3A—C3—H3B	107.8	C7—C11—C12	108.2 (2)
C15—C4—C3	109.7 (2)	C7—C11—C13	130.8 (3)
C15—C4—C5	113.8 (2)	C12—C11—C13	120.9 (2)
C3—C4—C5	111.89 (19)	O2—C12—O1	121.3 (3)
C15—C4—H4	107.0	O2—C12—C11	129.7 (2)
C3—C4—H4	107.0	O1—C12—C11	108.9 (2)
C5—C4—H4	107.0	C11—C13—H13A	109.5
C14—C5—C4	111.40 (18)	C11—C13—H13B	109.5
C14—C5—C6	109.80 (18)	H13A—C13—H13B	109.5
C4—C5—C6	109.48 (18)	C11—C13—H13C	109.5
C14—C5—C10	111.15 (18)	H13A—C13—H13C	109.5
C4—C5—C10	107.89 (17)	H13B—C13—H13C	109.5
C6—C5—C10	106.99 (16)	C5—C14—H14A	109.5
C7—C6—C5	110.60 (17)	C5—C14—H14B	109.5
C7—C6—H6A	109.5	H14A—C14—H14B	109.5
C5—C6—H6A	109.5	C5—C14—H14C	109.5
C7—C6—H6B	109.5	H14A—C14—H14C	109.5
C5—C6—H6B	109.5	H14B—C14—H14C	109.5
H6A—C6—H6B	108.1	C4—C15—H15A	109.5
C11—C7—C6	132.6 (2)	C4—C15—H15B	109.5
C11—C7—C8	109.9 (2)	H15A—C15—H15B	109.5
C6—C7—C8	117.24 (18)	C4—C15—H15C	109.5
O3—C8—O1	109.53 (17)	H15A—C15—H15C	109.5
O3—C8—C7	114.85 (19)	H15B—C15—H15C	109.5
O4—C1—C2—C3	126.2 (3)	O3—C8—C9—C10	−72.0 (2)
C10—C1—C2—C3	−53.2 (3)	O1—C8—C9—C10	168.34 (16)
C1—C2—C3—C4	51.1 (3)	C7—C8—C9—C10	53.8 (2)
C2—C3—C4—C15	177.4 (2)	O4—C1—C10—C9	6.0 (3)
C2—C3—C4—C5	−55.3 (3)	C2—C1—C10—C9	−174.5 (2)
C15—C4—C5—C14	59.4 (3)	O4—C1—C10—C5	−122.1 (2)
C3—C4—C5—C14	−65.6 (3)	C2—C1—C10—C5	57.3 (2)
C15—C4—C5—C6	−62.2 (3)	C8—C9—C10—C1	173.39 (16)
C3—C4—C5—C6	172.73 (19)	C8—C9—C10—C5	−60.4 (2)
C15—C4—C5—C10	−178.3 (2)	C14—C5—C10—C1	66.0 (2)
C3—C4—C5—C10	56.6 (2)	C4—C5—C10—C1	−56.4 (2)
C14—C5—C6—C7	69.0 (2)	C6—C5—C10—C1	−174.11 (18)
C4—C5—C6—C7	−168.42 (18)	C14—C5—C10—C9	−61.1 (2)
C10—C5—C6—C7	−51.8 (2)	C4—C5—C10—C9	176.45 (16)
C5—C6—C7—C11	−120.6 (2)	C6—C5—C10—C9	58.7 (2)
C5—C6—C7—C8	53.2 (2)	C6—C7—C11—C12	173.9 (2)
C12—O1—C8—O3	119.6 (2)	C8—C7—C11—C12	−0.3 (2)
C12—O1—C8—C7	−3.5 (2)	C6—C7—C11—C13	−3.7 (4)
C12—O1—C8—C9	−121.9 (2)	C8—C7—C11—C13	−177.9 (2)
C11—C7—C8—O3	−117.3 (2)	C8—O1—C12—O2	−177.8 (2)
C6—C7—C8—O3	67.5 (2)	C8—O1—C12—C11	3.5 (3)
C11—C7—C8—O1	2.3 (2)	C7—C11—C12—O2	179.5 (3)
C6—C7—C8—O1	−172.85 (17)	C13—C11—C12—O2	−2.6 (4)
C11—C7—C8—C9	121.1 (2)	C7—C11—C12—O1	−2.0 (3)
C6—C7—C8—C9	−54.0 (2)	C13—C11—C12—O1	175.8 (2)

D—H···A	D—H	H···A	D···A	D—H···A
O3—H3···O4i	0.90 (4)	1.87 (4)	2.750 (3)	164 (4)

Table 1

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H3⋯O4i	0.90 (4)	1.87 (4)	2.750 (3)	164 (4)

Symmetry code: (i) .