[1a(1a[alpha],5[beta],9a[alpha])]-1,1a,4,5,7,8,9,9a-Octahydro-3-hydroxy-1,1,2,5-tetramethyl-7-methylene-6H-cyclopropa[3,4]cyclo­hept[1,2-e]inden-6-one

Interest in the title structure, C₂₀H₂₄O₂, lies in the novel cis ring junction between the three- and seven-membered rings. This stereochemical arrangement causes the methylene moiety and the cycloheptane ring to be twisted out of the plane of the aromatic ring. The cyclopropane ring is also twisted out of the plane of the aromatic system. The molecules are linked by an O-H...O hydrogen bond [O...O 2.741 (3) Å].

S1. Comment

Jatropholone (JOH), a natural phorbol-related mixture of diterpenes (JOH-A and JOH-B), was isolated from the hexane extract of Jatropha elliptica (Goulart et al., 1993). Its acetate was previously characterized by X-ray diffraction (Purushothaman et al., 1979). The tetracyclic array, consisting of fused five-, six-, seven- and three-membered rings with two potentially electroactive functionalities, suggests the possibility of interesting chemical transformations. However, apart from the total synthesis (Smith et al., 1986), little chemical information concerning the reactivity has been available. Recently, the diastereomeric mixture was investigated by electroanalysis (De Azevedo et al., 1998) and subjected to electrochemical and chemical reductions. Electrolysis (Hg cathode, DMF/TBAP) and catalytic hydrogenation (H₂/PtO₂) lead, in both processes, to high chemo- and stereoselectivities (De Azevedo et al., 1998). The phenolic proton and the positioning of the seven- and three-membered rings appear to play a very important role in the process. To understand the selectivities, structural information on the non-derivatized substrate is a fundamental requirement. Jatropholone A (JOH-A), (I), was therefore purified and its three-dimensionl structure determined by crystallographic analysis.

The five-membered ring has an envelope conformation, in which C5 is 0.259 (5) Å out of the plane formed by the remaining four atoms. The Cremer & Pople (1975) ring puckering parameters are q₂ = 1.85 (4) Å and ϕ₂ = 182 (1)° [Editorial note: PARST gives q₂ = 0.167 (3) Å and ϕ₂ = 85.0 (10)°]. The dihedral angle between the five-membered ring and six-membered aromatic ring is 5.6 (1)°. Atoms C1A and C7 are nearly coplanar with the aromatic ring, with distances of 0.068 (5) and 0.158 (5) Å, respectively, out of that plane. Atom C14 of the methylene group is located above the average plane of the aromatic ring, whereas atom C1 of the cyclopropane ring is below the plane. The distances of atoms C14 and C1 from this plane are, respectively, 1.308 (6) and -1.016 (6) Å.

The absolute stereochemistry could not be determined from the present data. The coordinates reflect only relative stereochemistry at the chiral centres. The stereochemistry of the H atoms of C1A and C9A, where the cyclopropane ring is fused to the cycloheptane ring, is cis. As measured by the C6A—C6B—C7—C14 torsion angle, the methylene moiety of the cycloheptane ring is twisted out of the plane of the aromatic ring system by 73.1 (1)°. The cyclopropane ring is twisted out of the plane of the aromatic system by 48.8 (2)°. The structure therefore demonstrates that, in the formation of the hydrogenated product JOHH-2, the reaction has occurred on the least sterically hindered side of the molecule.

The molecules are linked by hydrogen bonding: O2···O1ⁱ = 2.741 (3), HO2···O1ⁱ = 1.96, O2—HO2 = 0.82 Å, O2—HO2···O1ⁱ = 159°; symmetry code: (i) = -1/2 + x, 3/2 - y, 1/4 - z]. In addition, the shortest C···O contact may also represent a hydrogen bond: C13···O2ⁱⁱ = 3.335 (4), H13A···O2ⁱⁱ = 2.52 Å, C13A—H13A···O2ⁱⁱ = 143°; symmetry code: (ii) 1/2 + x, 3/2 - y, 1/4 - z.

A ZORTEP (Zsolnai, 1995) illustration of the formula unit is presented in Fig. 1.

S2. Experimental

After isolation from the hexane extract of the plant, named following the Muell (Arg) classification system, Jatropha elliptica (Goulart et al.1993), the diastereomeric mixture of jatropholones (0.100 g) was submitted to flash chromatography on a silica-gel (230–400 mesh, Merck) column (internal diameter 2 cm; silica height 31 cm), using a mixture of hexane/ethylacetate (9:1 v/v) as eluent, collecting fractions of 10 ml. The column chromotography was followed by thin-layer chromotography (TLC), on silica-gel 60 F₂₅₄ plates (layer thickness 0.2 mm, Riedel-deHaën), using the same eluent and two consecutive runs. TLC spots were visualized by UV irradiation and developed by using phosphomolybdic acid solution in ethanol (10%). The less-polar compound (JOH-A) was eluted first and left to crystallize in the same solvent system.

S3. Refinement

All the H atoms were located on Fourier difference maps. The H-atom positions were fixed and an overall isotropic displacement parameter was refined to U = 0.093 (4) Ų. The absolute stereochemistry could not be determined from refinement of the present data. No reflections related by Friedel symmetry were included in the final refinement, which otherwise included all of the independent intensities measured to θ = 25°.

Data collection: CAD-4 Software (Enraf–Nonius, 1989). Cell refinement: CAD-4 Software. Data reduction: CAD-4 Software. Program(s) used to solve structure: SHELXS86 (Sheldrick, 1990). Program(s) used to refine structure: SHELXL97 (Sheldrick, 1997). Molecular graphics: ZORTEP (Zsolnai, 1995).

Computing details

Figures

Fig. 1. Projection of the title compound, showing the atom labelling with 50% probability displacement ellipsoids for non-H atoms. H atoms are of arbitrary sizes.

(I)

Crystal data

C20H24O2	Dx = 1.170 Mg m^−3
Mr = 296.39	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P43212	Cell parameters from 25 reflections
a = 13.378 (2) Å	θ = 9.1–25.0°
c = 18.803 (6) Å	µ = 0.07 mm^−1
V = 3365.2 (13) Å^3	T = 293 K
Z = 8	Irregular, colourless
F(000) = 1280	0.45 × 0.35 × 0.30 mm

Data collection

Nonius CAD-4 diffractometer	Rint = 0.030
Radiation source: fine-focus sealed tube	θmax = 25.0°, θmin = 1.9°
Graphite monochromator	h = 0→15
ω/2θ scans	k = −15→15
6369 measured reflections	l = 0→22
2975 independent reflections	3 standard reflections every 120 min
2357 reflections with I > 2σ(I)	intensity decay: 0.4%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.057	H-atom parameters constrained
wR(F^2) = 0.125	w = 1/[σ^2(Fo^2) + (0.0773P)^2 + 0.0458P] where P = (Fo^2 + 2Fc^2)/3
S = 1.16	(Δ/σ)max < 0.001
2975 reflections	Δρmax = 0.16 e Å^−3
204 parameters	Δρmin = −0.24 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.021 (2)

Special details

Experimental. From hexane/ethylacetate (9:1)

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O2	0.82925 (14)	0.91474 (15)	0.08004 (12)	0.0521 (5)
H2	0.8142	0.8564	0.0881	0.078*
C6A	1.0958 (2)	0.8696 (2)	0.10962 (15)	0.0420 (7)
C3	0.92836 (19)	0.92812 (19)	0.09233 (14)	0.0385 (6)
C2	0.9625 (2)	1.02591 (19)	0.09787 (14)	0.0409 (6)
O1	1.23230 (17)	0.76079 (16)	0.14012 (14)	0.0703 (7)
C1B	1.0645 (2)	1.04524 (19)	0.10970 (13)	0.0418 (7)
C4	0.9749 (2)	0.73985 (19)	0.08873 (17)	0.0475 (7)
H4A	0.9405	0.7262	0.0444	0.057*
H4B	0.9349	0.7148	0.1279	0.057*
C3A	0.9953 (2)	0.8498 (2)	0.09700 (15)	0.0415 (6)
C6	1.1485 (2)	0.7734 (2)	0.11625 (16)	0.0481 (7)
C6B	1.1330 (2)	0.96686 (19)	0.11459 (15)	0.0445 (7)
C12	0.8870 (2)	1.1084 (2)	0.08889 (18)	0.0520 (7)
H12A	0.8549	1.1019	0.0435	0.078*
H12B	0.9202	1.1720	0.0915	0.078*
H12C	0.8379	1.1041	0.1260	0.078*
C13	1.0874 (3)	0.5935 (2)	0.1273 (2)	0.0710 (11)
H13A	1.1542	0.5681	0.1225	0.107*
H13B	1.0411	0.5469	0.1068	0.107*
H13C	1.0722	0.6025	0.1768	0.107*
C7	1.2421 (2)	0.9881 (2)	0.11894 (19)	0.0544 (8)
C5	1.0793 (2)	0.6931 (2)	0.08902 (17)	0.0491 (7)
H5	1.0974	0.6810	0.0393	0.059*
C1A	1.1026 (2)	1.1505 (2)	0.11230 (16)	0.0483 (7)
H1A	1.1137	1.1803	0.0653	0.058*
C9A	1.1788 (3)	1.1806 (2)	0.16691 (17)	0.0608 (8)
H9A	1.2311	1.2256	0.1492	0.073*
C10	1.0075 (3)	1.2002 (3)	0.22984 (19)	0.0770 (11)
H10A	1.0036	1.1289	0.2349	0.116*
H10B	0.9421	1.2265	0.2202	0.116*
H10C	1.0326	1.2289	0.2731	0.116*
C1	1.0764 (3)	1.2257 (2)	0.16948 (18)	0.0601 (9)
C9	1.2135 (3)	1.1061 (2)	0.22084 (18)	0.0691 (10)
H9B	1.1558	1.0736	0.2419	0.083*
H9C	1.2491	1.1407	0.2584	0.083*
C14	1.2995 (3)	0.9752 (3)	0.0630 (2)	0.0728 (10)
H14A	1.2721	0.9529	0.0204	0.087*
H14B	1.3676	0.9886	0.0659	0.087*
C8	1.2817 (3)	1.0270 (3)	0.18853 (19)	0.0735 (10)
H8A	1.3476	1.0555	0.1810	0.088*
H8B	1.2886	0.9718	0.2217	0.088*
C11	1.0670 (4)	1.3336 (2)	0.1444 (2)	0.0843 (13)
H11A	1.0783	1.3779	0.1838	0.126*
H11B	1.0011	1.3445	0.1258	0.126*
H11C	1.1156	1.3464	0.1080	0.126*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O2	0.0367 (10)	0.0377 (10)	0.0819 (13)	−0.0032 (8)	−0.0063 (10)	0.0079 (11)
C6A	0.0387 (14)	0.0350 (14)	0.0523 (16)	−0.0001 (12)	0.0006 (12)	0.0040 (12)
C3	0.0318 (14)	0.0335 (14)	0.0503 (14)	−0.0002 (10)	−0.0003 (12)	0.0034 (12)
C2	0.0399 (15)	0.0349 (14)	0.0480 (14)	0.0000 (11)	−0.0005 (12)	0.0019 (12)
O1	0.0446 (12)	0.0401 (12)	0.1262 (19)	0.0082 (9)	−0.0093 (13)	0.0114 (13)
C1B	0.0475 (16)	0.0311 (14)	0.0469 (15)	−0.0031 (12)	−0.0058 (13)	0.0030 (11)
C4	0.0452 (16)	0.0317 (14)	0.0657 (17)	−0.0024 (12)	0.0030 (14)	−0.0031 (13)
C3A	0.0405 (15)	0.0333 (14)	0.0506 (15)	−0.0046 (11)	0.0037 (12)	0.0013 (12)
C6	0.0390 (16)	0.0348 (15)	0.0705 (18)	0.0025 (12)	0.0073 (14)	0.0057 (14)
C6B	0.0427 (15)	0.0342 (14)	0.0564 (16)	−0.0047 (12)	−0.0058 (13)	0.0029 (13)
C12	0.0516 (18)	0.0351 (15)	0.0693 (19)	0.0040 (13)	−0.0089 (15)	0.0024 (13)
C13	0.0525 (18)	0.0347 (15)	0.126 (3)	0.0041 (15)	0.005 (2)	0.0088 (19)
C7	0.0391 (16)	0.0395 (15)	0.084 (2)	−0.0047 (13)	−0.0106 (16)	0.0114 (15)
C5	0.0490 (17)	0.0340 (15)	0.0642 (17)	0.0023 (12)	0.0114 (15)	−0.0025 (13)
C1A	0.0516 (17)	0.0317 (14)	0.0618 (17)	−0.0080 (12)	−0.0101 (15)	0.0089 (13)
C9A	0.065 (2)	0.0412 (17)	0.0763 (19)	−0.0158 (14)	−0.0166 (17)	0.0069 (15)
C10	0.093 (3)	0.064 (2)	0.074 (2)	−0.002 (2)	−0.005 (2)	−0.0128 (18)
C1	0.076 (2)	0.0317 (15)	0.0729 (19)	−0.0051 (15)	−0.0181 (18)	−0.0023 (15)
C9	0.082 (2)	0.0524 (19)	0.073 (2)	−0.0080 (18)	−0.0313 (19)	0.0037 (16)
C14	0.0405 (18)	0.071 (2)	0.107 (3)	−0.0043 (18)	−0.0009 (19)	0.008 (2)
C8	0.060 (2)	0.063 (2)	0.098 (3)	−0.0035 (18)	−0.028 (2)	0.013 (2)
C11	0.112 (3)	0.0332 (17)	0.108 (3)	−0.0012 (19)	−0.034 (3)	−0.0035 (19)

Geometric parameters (Å, º)

O2—C3	1.358 (3)	C6—C5	1.507 (4)
C6A—C3A	1.390 (4)	C6B—C7	1.490 (4)
C6A—C6B	1.397 (4)	C13—C5	1.518 (4)
C6A—C6	1.473 (4)	C7—C14	1.314 (5)
C3—C3A	1.381 (4)	C7—C8	1.505 (5)
C3—C2	1.390 (4)	C1A—C9A	1.502 (4)
C2—C1B	1.406 (4)	C1A—C1	1.513 (5)
C2—C12	1.506 (4)	C9A—C9	1.496 (4)
O1—C6	1.219 (4)	C9A—C1	1.497 (5)
C1B—C6B	1.396 (4)	C10—C1	1.502 (5)
C1B—C1A	1.498 (4)	C1—C11	1.524 (4)
C4—C3A	1.504 (4)	C9—C8	1.523 (5)
C4—C5	1.530 (4)
C3A—C6A—C6B	122.2 (2)	C6A—C6B—C7	122.0 (2)
C3A—C6A—C6	108.2 (2)	C14—C7—C6B	120.3 (3)
C6B—C6A—C6	129.6 (2)	C14—C7—C8	122.4 (3)
O2—C3—C3A	123.0 (2)	C6B—C7—C8	117.3 (3)
O2—C3—C2	117.2 (2)	C6—C5—C13	114.8 (3)
C3A—C3—C2	119.8 (2)	C6—C5—C4	105.7 (2)
C3—C2—C1B	120.3 (2)	C13—C5—C4	115.2 (2)
C3—C2—C12	117.5 (2)	C1B—C1A—C9A	120.4 (2)
C1B—C2—C12	122.2 (3)	C1B—C1A—C1	124.7 (3)
C6B—C1B—C2	120.6 (3)	C9A—C1A—C1	59.5 (2)
C6B—C1B—C1A	118.7 (2)	C9—C9A—C1	122.0 (3)
C2—C1B—C1A	120.6 (2)	C9—C9A—C1A	119.6 (3)
C3A—C4—C5	103.5 (2)	C1—C9A—C1A	60.6 (2)
C3—C3A—C6A	119.6 (2)	C9A—C1—C10	119.7 (3)
C3—C3A—C4	128.2 (3)	C9A—C1—C1A	59.9 (2)
C6A—C3A—C4	112.3 (2)	C10—C1—C1A	121.9 (3)
O1—C6—C6A	126.3 (3)	C9A—C1—C11	116.6 (3)
O1—C6—C5	126.2 (3)	C10—C1—C11	113.4 (3)
C6A—C6—C5	107.4 (2)	C1A—C1—C11	115.4 (3)
C1B—C6B—C6A	117.5 (2)	C9A—C9—C8	112.3 (3)
C1B—C6B—C7	120.3 (2)	C7—C8—C9	112.1 (3)