Two (+)-α,4-dimethyl-2-oxocyclo­hexaneacetic acids: hydrogen bonding in a terpenoid γ-keto acid and in a diastereomeric lactol

The (+)-(αS,1S,4R)-diastereomer of the title structure, C₁₀H₁₆O₃, aggregates in the solid as non-symmetric dimers with disorder in both carboxyl groups [O...O = 2.710 (5) and 2.638 (5) Å]. The two mol­ecules constituting the asymmetric unit pair around a pseudo-twofold rotational axis and differ only slightly in their distances and angles, but one methyl group displays rotational disorder absent in the other mol­ecule. Five inter­molecular C—H...O close contacts exist, involving both ketone groups. The (+)-(αR,1R,4R)-diastereomer exists in the crystal in its closed-ring lactol form, (3R,3aR,6R,7aR)-2,3,3a,4,5,6,7,7a-octa­hydro-7a-hydroxy-3,6-dimethyl­benzo[b]furan-2-one, C₁₀H₁₆O₃, and aggregates as hydrogen-bonded catemers that extend from the hydroxyl group of one mol­ecule to the carbonyl group of a neighbor screw-related along b [O...O = 2.830 (3) Å and O—H...O = 169°]. One close inter­molecular C—H...O contact exists involving the carbonyl group.

S1. Comment

Our study of hydrogen bonding in solid ketocarboxylic acids has included several γ- and δ-keto acids that crystallize as lactols (Thompson et al., 1985; Papadakis et al., 2003). We now report results for a diastereomeric pair of γ-keto acids having the title structure, of which one crystallizes in the open-chain and the other in the lactol form. Both are derived from the same source, an optically active conjugated terpene lactone isolatable from oil of peppermint and reported to have analgesic properties. Given the fixed configuration at one of the three stereogenic centers in our compounds, the remaining two, the configurations of which are alterable, can generate four diastereomeric permutations. Two of these four compounds are evidently liquids at room temperature (Foote et al., 1967). We describe here the remaining two, which are crystalline (Foote et al., 1967; Woodward & Eastman, 1950; Takahashi et al., 1979). One, (+)-(αS,1S,4R), is the monocyclic keto acid, (I), while its diastereomer, (+)-(αR,1R,4R), crystallizes in the bicyclic lactol (`pseudoacid') form, (II).

Fig. 1 shows the asymmetric unit for compound (I). The two molecules, designated (IA) and (IB), differ slightly in their conformations. Both ring substituents of (I) lie on equatorial bonds, and the specific staggered conformation about C1—C7 is energetically advantageous in placing both C7 substituents in anti relationships relative to the ring bonds. The one remaining conformationally significant option is rotation of the carboxyl group, which differs in (IA) and (IB) by 5.2 (8)° (for the C1—C7—C8—O2 torsion angles). The resulting dihedral angle between the plane of the carboxyl group (O2/O3/C8/C7) and that of the ketone (C1/C2/C3/O1) is 82.35 (18)° for (IA) and 80.51 (17)° for (IB). Superimposing the two halves of the asymmetric unit shows that the positional differences for correlated atom pairs range from 0.017 Å (for atom C4) to 0.092 Å (for atom O2). The largest variation in torsion angle between (IA) and (IB) is 3.27 (6)° for C3—C4—C5—C6. The superimposition for the full molecules of (IA) and (IB) produces an overall r.m.s. deviation of 0.10 Å, which diminishes to 0.06 Å when the H atoms are omitted. Consistent with most of the differences residing in the H-atom positions, in (IB) the methyl group adjacent to the carboxyl group is disordered, with an 86:14 (6) distribution of contributors, while molecule (IA) lacks this methyl disorder.

All these minor conformational differences are only part of a larger constellation of non-symmetric `flaws', which conspire to thwart what would otherwise constitute a twofold axis of rotation relating (IA) and (IB). For example, the two halves of the dimer are also imperfectly aligned about their potential twofold axis by a slight central folding of the dimer, an out-of-plane `hinging', with a dihedral angle of 2.7 (13)° rather than exactly 0°. Thus, even forcing the identity of (IA) and (IB) does not create a true twofold axis (and fails to produce any additional symmetry), nor does a contrived twofold axis align with any crystallographic element. Such an absence of any element of symmetry in carboxyl dimers (Lalancette et al., 1991, 1996; Lalancette & Thompson, 2003) is much more commonly encountered in chiral nonracemic cases, such as (I), than where centrosymmetric arrangements are possible (Gavezzotti & Filippini, 1994; Allen et al., 1999; Sørensen & Larsen, 2003).

Many dimerized carboxyl groups have C—O bond lengths and C—C—O angles fully or partially averaged by disorder. The mechanisms involved in transposing the carboxyl O atoms require only local centrosymmetry within the dimerized carboxyl grouping itself, and thus may still operate, as in the present case, in dimers lacking overall centrosymmetry. Thus, within the conventional limits of experimental error, both groups display total carboxyl disorder (Table 1).

Fig. 2 illustrates the packing of the cell for (I) with the heterogeneous dimers of the asymmetric unit. This packing includes five intermolecular C—H···O close contacts (Table 2), involving both ketones of the system and lying within the 2.7 Å range normally employed for non-bonded C—H···O packing interactions (Steiner, 1997; Steiner & Desiraju, 1998).

Fig. 3 shows the asymmetric unit for the (+)-(αR,1R,4R) isomer, (II), which crystallizes as the lactol. The numbering employed for (II) is identical to that used for (I), rather than the systematic but more complex benzofuran-based alternative (see Abstract), which obscures the parentage of (II) and its relationship to (I). Besides its new (R) lactol stereocenter at C2, compound (II) has configurations opposite to those in (I) at both C7 and C1; the latter creates a cis-1,4-disubstitution pattern for the cyclohexane, which requires that any chair conformation has an axial substituent. Placing the carboxyl-bearing substituent on an axial bond obviously allows the carboxyl group to approach the ketone from a direction favorable for the ring closure involved, but this will not automatically favor the lactol in the ring–chain equilibrium.

Many γ- and especially β-carboxy ketones and carboxy aldehydes with geometries permitting it exist at least partly as the lactols in liquid phases (Chadwick & Dunitz, 1979; Dobson & Gerkin, 1996; Valente et al., 1998). Although the factors affecting this tendency have been studied (Soffer et al., 1950; Jones, 1963), the open and closed forms often lie so close energetically that small changes in the structure or the medium can shift the equilibria appreciably (Valters & Flitsch, 1985), so that predictions regarding equilibrium values for specific cases remain hazardous. Some such keto acids crystallize exclusively as lactols (Thompson et al., 1985; Papadakis et al., 2003). However, with low energy barriers, the equilibria involved may shift even during crystallization, so that the particular tautomer obtained as the solid may actually depend more on crystallinity than on the position of the ring–chain equilibrium in the solution or melt. Our data (below) suggest that, in CHCl₃ solution, (II) exists as a mixture containing a minor amount of the open form.

Fig. 4 shows the packing for (II) and the pattern for its hydrogen bonding. With no intramolecular hydrogen bonding possible, the molecule adopts the intermolecular mode commonly seen in such lactols, a hydroxyl-to-carbonyl catemer. As happens frequently (Papadakis et al., 2003), the units of the chain are screw-related, in this case following the b axis in both directions. We characterize the geometry of hydrogen bonding to carbonyl groups using a combination of the H···O═C angle (ideal value 120°) and the H···O═C—C torsion angle (ideal value 0°). For the hydrogen bonding in (II), the above angles are 126 and 34°, respectively. A single C—H···O close contact (2.66 Å) was found, to the carbonyl O atom from atom H1B in the same screw-related neighbor involved in the catemeric hydrogen-bonding connection.

The solid-state (KBr) IR spectrum of (I) has a single C═O absorption at 1704 cm⁻¹ for both carboxyl and ketone, typical of unstrained dimeric cases lacking conjugation. This absorption is little changed in CHCl₃ solution (1707 cm⁻¹), where dimers predominate. For (II), the peak at 1736 cm⁻¹ in the KBr spectrum conforms to C═O shifts typical for hydrogen bonding to a γ-lactone, whereas in CHCl₃ solution this peak is positioned normally, at 1764 cm⁻¹. Notably, the solution spectrum of (II) also contains a smaller peak, not present in the KBr spectrum, at a position (1708 cm⁻¹) consistent with both carbonyl groups in the open keto-acid form of the molecule. Assessing the relative concentrations of the open and closed forms of (II) from the C═O peak absorbance ratio (70:30), however, is limited by our lack of access to the pure open form, the peak of which at 1708 cm⁻¹ is due to both C═O groups present, while that at 1764 cm⁻¹ represents a single carbonyl group. ¹H NMR spectroscopy suggests the presence of about 5% of the minor tautomer in CDCl₃ solution.

S2. Experimental

(-)-Menthalactone (99% pure) was purchased from Sigma–Aldrich Chemicals, Milwaukee, Wisconsin, USA. Aqueous saponification as described by Foote et al. (1967) provided a concentrated oily product mixture that partially crystallized on refrigeration. Crystals of (I) suitable for X-ray analysis (m.p. 368 K) were obtained from diethyl ether, which was also used to separate (I) from (II) on the basis of differential solubility. Recrystallization of (II) from ethyl acetate gave material melting at 416 K, suitable for analysis. The absolute configurations of both (I) and (II) have been established previously (Foote et al., 1967; Takahashi et al., 1979). Although no [α]_D optical rotations appear to have been reported for either (I) or (II), the positive ORD Please define Cotton effects reported for both (Foote et al., 1967) permit the assignment of positive signs to their [α]_D rotations.

S3. Refinement

All H atoms for both (I) and (II) were found in electron-density difference maps but were placed in calculated positions, with C—H distances of 0.97 Å for methylene H atoms, 0.98 Å for methine H atoms and 0.96 Å for methyl H atoms, and with O—H distances of 0.82 Å for both the disordered half-occupied acid H atoms in (I) and the hydroxyl H atom in (II), and allowed to refine as riding models on their respective atoms, with U_iso(H) = 1.2U_eq(C) or 1.5U_eq(O). Please check added text. The data for both (I) and (II) were merged, yielding 2087 Friedel pairs for (I) and 1050 for (II).

Computing details

For both compounds, data collection: XSCANS (Siemens, 1996); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997a); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997a); molecular graphics: SHELXP97 (Sheldrick, 1997a); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The asymmetric unit in (I), with the unit cell and with the atom numbering shown only for (IA); (IB) is highlighted by open bonds. The disordered carboxyl groups are depicted with half-occupancy H atoms. For the partially disordered methyl group in (IB), the major contributor is shown with open bonds. Displacement ellipsoids are drawn at the 20% probability level.
	Fig. 2. A packing diagram for (I). For clarity, all C-bound H atoms have been omitted and molecules of type (IB) are represented with open bonds.
	Fig. 3. The asymmetric unit in (II), with skeletal numbering identical to that for (I). Displacement ellipsoids are drawn at the 20% probability level.
	Fig. 4. A packing diagram for (II) with extra molecules, illustrating the hydroxyl-to-carbonyl hydrogen bonding linking molecules screw-related along b. For clarity, all C-bound H atoms have been omitted.

(I) (+)-(αS,1S,4R)-α,4-dimethyl-2-oxocyclohexaneacetic acid

Crystal data

C10H16O3	Dx = 1.150 Mg m^−3
Mr = 184.23	Melting point: 368 K
Orthorhombic, P21212	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2 2ab	Cell parameters from 27 reflections
a = 16.740 (5) Å	θ = 2.5–8.8°
b = 19.173 (5) Å	µ = 0.08 mm^−1
c = 6.632 (2) Å	T = 296 K
V = 2128.4 (11) Å^3	Hexagonal plate, colorless
Z = 8	0.50 × 0.20 × 0.16 mm
F(000) = 800

Data collection

Siemens P4 diffractometer	1007 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.074
Graphite monochromator	θmax = 25.0°, θmin = 1.6°
2θ/θ scans	h = −19→19
Absorption correction: analytical (SHELXS97; Sheldrick, 1997a)	k = −22→22
Tmin = 0.980, Tmax = 0.990	l = −6→7
4249 measured reflections	3 standard reflections every 97 reflections
2162 independent reflections	intensity decay: variation <3.0%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.059	H-atom parameters constrained
wR(F^2) = 0.093	w = 1/[σ^2(Fo^2) + (0.012P)^2 + ] where P = (Fo^2 + 2Fc^2)/3
S = 0.98	(Δ/σ)max < 0.001
2162 reflections	Δρmax = 0.14 e Å^−3
238 parameters	Δρmin = −0.14 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997a), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0033 (4)

Special details

Experimental. crystal mounted on glass fiber using cyanoacrylate cement

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	Occ. (<1)
O1A	0.1428 (2)	0.7014 (2)	0.7865 (5)	0.0839 (13)
O2A	0.30444 (19)	0.63497 (18)	0.6320 (5)	0.0689 (11)
H2AA	0.3424	0.6345	0.7102	0.103*	0.50
O3A	0.3225 (2)	0.74901 (18)	0.6682 (5)	0.0776 (12)
H3AA	0.3569	0.7345	0.7456	0.116*	0.50
O1B	0.6061 (2)	0.64804 (18)	0.7705 (5)	0.0753 (12)
O2B	0.4392 (2)	0.72680 (18)	0.9278 (5)	0.0715 (12)
H2BA	0.4027	0.7262	0.8454	0.107*	0.50
O3B	0.4279 (2)	0.61107 (17)	0.8870 (5)	0.0740 (12)
H3BA	0.3915	0.6236	0.8129	0.111*	0.50
C1A	0.1519 (3)	0.6602 (3)	0.4477 (7)	0.0510 (13)
H1A	0.1731	0.6127	0.4345	0.061*
C1B	0.5801 (3)	0.5931 (2)	1.0860 (7)	0.0537 (14)
H1B	0.5482	0.5503	1.0772	0.064*
C2A	0.1142 (3)	0.6667 (3)	0.6540 (8)	0.0553 (15)
C2B	0.6242 (3)	0.6020 (3)	0.8874 (8)	0.0536 (15)
C3A	0.0359 (3)	0.6272 (3)	0.6828 (7)	0.0758 (18)
H3A1	0.0126	0.6405	0.8111	0.091*
H3A2	0.0470	0.5776	0.6875	0.091*
C3B	0.6889 (3)	0.5503 (3)	0.8450 (7)	0.0716 (17)
H3B1	0.7177	0.5649	0.7254	0.086*
H3B2	0.6646	0.5054	0.8162	0.086*
C4A	−0.0243 (3)	0.6415 (3)	0.5154 (7)	0.0668 (16)
H4A	−0.0381	0.6912	0.5191	0.080*
C4B	0.7481 (3)	0.5416 (3)	1.0180 (9)	0.0695 (16)
H4B	0.7762	0.5861	1.0348	0.083*
C5A	0.0151 (3)	0.6263 (3)	0.3151 (7)	0.0710 (16)
H5A1	−0.0227	0.6353	0.2072	0.085*
H5A2	0.0297	0.5774	0.3096	0.085*
C5B	0.7029 (3)	0.5272 (3)	1.2107 (8)	0.0748 (18)
H5B1	0.7404	0.5244	1.3218	0.090*
H5B2	0.6761	0.4825	1.1997	0.090*
C6A	0.0894 (3)	0.6709 (2)	0.2829 (7)	0.0661 (16)
H6A1	0.0741	0.7197	0.2797	0.079*
H6A2	0.1128	0.6594	0.1533	0.079*
C6B	0.6413 (3)	0.5835 (3)	1.2561 (8)	0.0803 (19)
H6B1	0.6686	0.6274	1.2787	0.096*
H6B2	0.6132	0.5714	1.3793	0.096*
C7A	0.2227 (3)	0.7115 (3)	0.4338 (7)	0.0594 (15)
H7A	0.2015	0.7584	0.4574	0.071*
C7B	0.5229 (3)	0.6537 (3)	1.1272 (7)	0.0589 (15)
H7B	0.5550	0.6964	1.1340	0.071*
C8A	0.2859 (3)	0.6981 (3)	0.5912 (8)	0.0557 (15)
C8B	0.4606 (3)	0.6645 (4)	0.9673 (8)	0.0596 (16)
C9A	0.2636 (3)	0.7119 (3)	0.2268 (8)	0.087 (2)
H9A1	0.2246	0.7211	0.1240	0.131*
H9A2	0.2879	0.6673	0.2028	0.131*
H9A3	0.3038	0.7476	0.2242	0.131*
C9B	0.4794 (3)	0.6461 (3)	1.3304 (7)	0.095 (2)
H9B1	0.5172	0.6504	1.4385	0.142*	0.86 (6)
H9B2	0.4542	0.6011	1.3370	0.142*	0.86 (6)
H9B3	0.4396	0.6819	1.3424	0.142*	0.86 (6)
H9B4	0.4235	0.6385	1.3068	0.142*	0.14 (6)
H9B5	0.4865	0.6878	1.4083	0.142*	0.14 (6)
H9B6	0.5011	0.6071	1.4028	0.142*	0.14 (6)
C10A	−0.1018 (3)	0.5991 (3)	0.5447 (9)	0.103 (2)
H10A	−0.1388	0.6103	0.4390	0.154*
H10B	−0.1251	0.6105	0.6728	0.154*
H10C	−0.0896	0.5502	0.5404	0.154*
C10B	0.8106 (3)	0.4856 (3)	0.9744 (8)	0.107 (2)
H10D	0.8466	0.4821	1.0865	0.160*
H10E	0.8400	0.4980	0.8553	0.160*
H10F	0.7846	0.4416	0.9538	0.160*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1A	0.079 (3)	0.125 (3)	0.048 (2)	0.005 (3)	−0.004 (2)	−0.015 (3)
O2A	0.055 (2)	0.070 (3)	0.081 (3)	0.007 (2)	−0.012 (2)	0.007 (2)
O3A	0.078 (3)	0.074 (3)	0.081 (3)	−0.013 (2)	−0.025 (2)	0.006 (2)
O1B	0.091 (3)	0.076 (3)	0.059 (2)	0.011 (2)	0.004 (2)	0.017 (2)
O2B	0.060 (3)	0.072 (3)	0.083 (3)	−0.002 (2)	−0.006 (2)	0.000 (2)
O3B	0.069 (3)	0.071 (3)	0.082 (3)	−0.014 (2)	−0.024 (2)	−0.001 (2)
C1A	0.043 (3)	0.069 (4)	0.041 (3)	0.012 (3)	0.003 (3)	0.004 (3)
C1B	0.053 (3)	0.054 (3)	0.054 (3)	−0.010 (3)	−0.003 (3)	0.002 (3)
C2A	0.050 (4)	0.070 (4)	0.046 (3)	0.015 (3)	−0.004 (3)	0.011 (3)
C2B	0.054 (4)	0.058 (4)	0.048 (3)	−0.006 (3)	−0.002 (3)	−0.006 (3)
C3A	0.062 (4)	0.107 (5)	0.058 (4)	0.002 (4)	0.007 (3)	0.013 (3)
C3B	0.091 (5)	0.069 (4)	0.055 (4)	0.024 (4)	0.013 (4)	−0.003 (3)
C4A	0.054 (4)	0.070 (4)	0.076 (4)	0.002 (3)	0.002 (4)	0.023 (3)
C4B	0.061 (4)	0.068 (4)	0.080 (4)	0.014 (3)	0.002 (4)	0.007 (4)
C5A	0.065 (4)	0.076 (4)	0.072 (4)	−0.013 (3)	−0.023 (4)	0.012 (3)
C5B	0.067 (4)	0.106 (5)	0.051 (4)	0.018 (4)	−0.008 (3)	0.011 (4)
C6A	0.067 (4)	0.088 (4)	0.044 (3)	−0.008 (3)	−0.009 (3)	0.004 (3)
C6B	0.062 (4)	0.121 (5)	0.057 (4)	0.027 (4)	−0.003 (4)	−0.014 (4)
C7A	0.052 (3)	0.075 (4)	0.051 (3)	0.000 (3)	0.002 (3)	0.002 (3)
C7B	0.052 (3)	0.072 (4)	0.053 (3)	−0.002 (3)	0.001 (3)	−0.012 (3)
C8A	0.052 (4)	0.066 (4)	0.049 (4)	0.004 (4)	0.006 (3)	0.003 (4)
C8B	0.046 (4)	0.083 (4)	0.050 (4)	−0.013 (4)	0.004 (3)	0.002 (4)
C9A	0.067 (4)	0.133 (5)	0.062 (4)	−0.005 (4)	0.006 (4)	0.025 (4)
C9B	0.074 (4)	0.152 (6)	0.058 (4)	0.024 (4)	−0.004 (4)	−0.011 (4)
C10A	0.066 (4)	0.113 (5)	0.130 (5)	−0.019 (4)	0.010 (4)	0.030 (5)
C10B	0.093 (5)	0.125 (5)	0.102 (5)	0.042 (5)	0.030 (4)	0.027 (5)

Geometric parameters (Å, º)

O1A—C2A	1.202 (5)	C5A—C6A	1.525 (6)
O2A—C8A	1.278 (5)	C5A—H5A1	0.9700
O2A—H2AA	0.8200	C5A—H5A2	0.9700
O3A—C8A	1.262 (5)	C5B—C6B	1.522 (6)
O3A—H3AA	0.8200	C5B—H5B1	0.9700
O1B—C2B	1.214 (5)	C5B—H5B2	0.9700
O2B—C8B	1.275 (5)	C6A—H6A1	0.9700
O2B—H2BA	0.8200	C6A—H6A2	0.9700
O3B—C8B	1.277 (6)	C6B—H6B1	0.9700
O3B—H3BA	0.8200	C6B—H6B2	0.9700
C1A—C2A	1.512 (6)	C7A—C8A	1.508 (6)
C1A—C6A	1.527 (6)	C7A—C9A	1.534 (6)
C1A—C7A	1.542 (6)	C7A—H7A	0.9800
C1A—H1A	0.9800	C7B—C8B	1.501 (6)
C1B—C2B	1.520 (6)	C7B—C9B	1.539 (6)
C1B—C7B	1.530 (6)	C7B—H7B	0.9800
C1B—C6B	1.535 (6)	C9A—H9A1	0.9600
C1B—H1B	0.9800	C9A—H9A2	0.9600
C2A—C3A	1.524 (7)	C9A—H9A3	0.9600
C2B—C3B	1.494 (6)	C9B—H9B1	0.9599
C3A—C4A	1.525 (6)	C9B—H9B2	0.9599
C3A—H3A1	0.9700	C9B—H9B3	0.9599
C3A—H3A2	0.9700	C9B—H9B4	0.9599
C3B—C4B	1.525 (7)	C9B—H9B5	0.9599
C3B—H3B1	0.9700	C9B—H9B6	0.9599
C3B—H3B2	0.9700	C10A—H10A	0.9600
C4A—C5A	1.511 (6)	C10A—H10B	0.9600
C4A—C10A	1.542 (6)	C10A—H10C	0.9600
C4A—H4A	0.9800	C10B—H10D	0.9600
C4B—C5B	1.510 (7)	C10B—H10E	0.9600
C4B—C10B	1.527 (6)	C10B—H10F	0.9600
C4B—H4B	0.9800
C8A—O2A—H2AA	109.5	C5B—C6B—C1B	113.1 (4)
C8A—O3A—H3AA	109.5	C5B—C6B—H6B1	109.0
C8B—O2B—H2BA	109.5	C1B—C6B—H6B1	109.0
C8B—O3B—H3BA	109.5	C5B—C6B—H6B2	109.0
C2A—C1A—C6A	110.5 (4)	C1B—C6B—H6B2	109.0
C2A—C1A—C7A	108.8 (4)	H6B1—C6B—H6B2	107.8
C6A—C1A—C7A	113.4 (4)	C8A—C7A—C9A	107.9 (4)
C2A—C1A—H1A	108.0	C8A—C7A—C1A	112.8 (4)
C6A—C1A—H1A	108.0	C9A—C7A—C1A	113.6 (4)
C7A—C1A—H1A	108.0	C8A—C7A—H7A	107.4
C2B—C1B—C7B	112.0 (4)	C9A—C7A—H7A	107.4
C2B—C1B—C6B	109.0 (4)	C1A—C7A—H7A	107.4
C7B—C1B—C6B	112.2 (4)	C8B—C7B—C1B	114.4 (4)
C2B—C1B—H1B	107.8	C8B—C7B—C9B	107.6 (4)
C7B—C1B—H1B	107.8	C1B—C7B—C9B	112.3 (4)
C6B—C1B—H1B	107.8	C8B—C7B—H7B	107.4
O1A—C2A—C1A	122.7 (5)	C1B—C7B—H7B	107.4
O1A—C2A—C3A	121.7 (5)	C9B—C7B—H7B	107.4
C1A—C2A—C3A	115.6 (5)	O3A—C8A—O2A	121.9 (5)
O1B—C2B—C3B	122.9 (5)	O3A—C8A—C7A	119.3 (5)
O1B—C2B—C1B	120.9 (5)	O2A—C8A—C7A	118.6 (5)
C3B—C2B—C1B	116.2 (5)	O2B—C8B—O3B	123.0 (5)
C2A—C3A—C4A	112.8 (4)	O2B—C8B—C7B	118.0 (5)
C2A—C3A—H3A1	109.0	O3B—C8B—C7B	118.8 (6)
C4A—C3A—H3A1	109.0	C7A—C9A—H9A1	109.5
C2A—C3A—H3A2	109.0	C7A—C9A—H9A2	109.5
C4A—C3A—H3A2	109.0	H9A1—C9A—H9A2	109.5
H3A1—C3A—H3A2	107.8	C7A—C9A—H9A3	109.5
C2B—C3B—C4B	113.6 (4)	H9A1—C9A—H9A3	109.5
C2B—C3B—H3B1	108.8	H9A2—C9A—H9A3	109.5
C4B—C3B—H3B1	108.8	C7B—C9B—H9B1	109.5
C2B—C3B—H3B2	108.8	C7B—C9B—H9B2	109.5
C4B—C3B—H3B2	108.8	H9B1—C9B—H9B2	109.5
H3B1—C3B—H3B2	107.7	C7B—C9B—H9B3	109.5
C5A—C4A—C3A	108.5 (4)	H9B1—C9B—H9B3	109.5
C5A—C4A—C10A	112.1 (5)	H9B2—C9B—H9B3	109.5
C3A—C4A—C10A	111.7 (4)	C7B—C9B—H9B4	109.5
C5A—C4A—H4A	108.2	H9B1—C9B—H9B4	141.1
C3A—C4A—H4A	108.2	H9B2—C9B—H9B4	56.3
C10A—C4A—H4A	108.2	H9B3—C9B—H9B4	56.3
C5B—C4B—C3B	109.3 (4)	C7B—C9B—H9B5	109.5
C5B—C4B—C10B	112.1 (5)	H9B1—C9B—H9B5	56.3
C3B—C4B—C10B	112.3 (5)	H9B2—C9B—H9B5	141.1
C5B—C4B—H4B	107.6	H9B3—C9B—H9B5	56.3
C3B—C4B—H4B	107.6	H9B4—C9B—H9B5	109.5
C10B—C4B—H4B	107.6	C7B—C9B—H9B6	109.5
C4A—C5A—C6A	111.8 (4)	H9B1—C9B—H9B6	56.3
C4A—C5A—H5A1	109.3	H9B2—C9B—H9B6	56.3
C6A—C5A—H5A1	109.3	H9B3—C9B—H9B6	141.1
C4A—C5A—H5A2	109.3	H9B4—C9B—H9B6	109.5
C6A—C5A—H5A2	109.3	H9B5—C9B—H9B6	109.5
H5A1—C5A—H5A2	107.9	C4A—C10A—H10A	109.5
C4B—C5B—C6B	112.2 (4)	C4A—C10A—H10B	109.5
C4B—C5B—H5B1	109.2	H10A—C10A—H10B	109.5
C6B—C5B—H5B1	109.2	C4A—C10A—H10C	109.5
C4B—C5B—H5B2	109.2	H10A—C10A—H10C	109.5
C6B—C5B—H5B2	109.2	H10B—C10A—H10C	109.5
H5B1—C5B—H5B2	107.9	C4B—C10B—H10D	109.5
C5A—C6A—C1A	112.6 (4)	C4B—C10B—H10E	109.5
C5A—C6A—H6A1	109.1	H10D—C10B—H10E	109.5
C1A—C6A—H6A1	109.1	C4B—C10B—H10F	109.5
C5A—C6A—H6A2	109.1	H10D—C10B—H10F	109.5
C1A—C6A—H6A2	109.1	H10E—C10B—H10F	109.5
H6A1—C6A—H6A2	107.8
C6A—C1A—C2A—O1A	−132.6 (5)	C2A—C1A—C6A—C5A	−50.0 (6)
C7A—C1A—C2A—O1A	−7.5 (7)	C7A—C1A—C6A—C5A	−172.5 (4)
C6A—C1A—C2A—C3A	46.3 (6)	C4B—C5B—C6B—C1B	57.5 (6)
C7A—C1A—C2A—C3A	171.4 (4)	C2B—C1B—C6B—C5B	−50.8 (6)
C7B—C1B—C2B—O1B	−8.6 (7)	C7B—C1B—C6B—C5B	−175.4 (4)
C6B—C1B—C2B—O1B	−133.3 (5)	C2A—C1A—C7A—C8A	59.4 (5)
C7B—C1B—C2B—C3B	172.6 (4)	C6A—C1A—C7A—C8A	−177.2 (4)
C6B—C1B—C2B—C3B	48.0 (6)	C2A—C1A—C7A—C9A	−177.4 (4)
O1A—C2A—C3A—C4A	129.0 (5)	C6A—C1A—C7A—C9A	−54.0 (6)
C1A—C2A—C3A—C4A	−49.9 (6)	C2B—C1B—C7B—C8B	58.3 (5)
O1B—C2B—C3B—C4B	131.0 (5)	C6B—C1B—C7B—C8B	−178.8 (5)
C1B—C2B—C3B—C4B	−50.3 (6)	C2B—C1B—C7B—C9B	−178.6 (4)
C2A—C3A—C4A—C5A	54.1 (6)	C6B—C1B—C7B—C9B	−55.7 (5)
C2A—C3A—C4A—C10A	178.1 (5)	C9A—C7A—C8A—O3A	89.3 (6)
C2B—C3B—C4B—C5B	51.9 (6)	C1A—C7A—C8A—O3A	−144.4 (5)
C2B—C3B—C4B—C10B	176.9 (4)	C9A—C7A—C8A—O2A	−85.8 (6)
C3A—C4A—C5A—C6A	−58.9 (6)	C1A—C7A—C8A—O2A	40.5 (6)
C10A—C4A—C5A—C6A	177.3 (4)	C1B—C7B—C8B—O2B	−144.8 (5)
C3B—C4B—C5B—C6B	−55.6 (6)	C9B—C7B—C8B—O2B	89.6 (6)
C10B—C4B—C5B—C6B	179.2 (5)	C1B—C7B—C8B—O3B	39.7 (6)
C4A—C5A—C6A—C1A	58.6 (6)	C9B—C7B—C8B—O3B	−85.9 (6)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1A···O2^i	0.82	2.02	2.710 (5)	169
O1—H1A···O2^i	0.82	2.02	2.638 (5)	169
C6A—H6A1···O1A^ii	0.97	2.61	3.461 (6)	146
C7B—H7B···O1A^iii	0.98	2.51	3.475 (6)	170
C9A—H9A1···O1A^ii	0.96	2.65	3.558 (6)	158
C6A—H6A2···O1B^iv	0.97	2.61	3.501 (6)	152
C9B—H9B1···O1B^v	0.96	2.66	3.608 (6)	170

Symmetry codes: (i) −x+5/2, y+1/2, −z+1; (ii) x, y, z+1; (iii) x−1/2, −y+1/2, −z; (iv) x+1/2, −y+1/2, −z+1; (v) x, y, z−1.

(II) (+)-(3R,3aR,6R,7aR)-hexahydro-7a-hydroxy-3,6-dimethylbenzo[a]furan-2-one'

Crystal data

C10H16O3	Dx = 1.230 Mg m^−3
Mr = 184.23	Melting point: 416 K
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 29 reflections
a = 6.728 (2) Å	θ = 1.9–10.6°
b = 7.455 (2) Å	µ = 0.09 mm^−1
c = 19.829 (5) Å	T = 296 K
V = 994.6 (5) Å^3	Plate, colorless
Z = 4	0.50 × 0.40 × 0.10 mm
F(000) = 400

Data collection

Siemens P4 diffractometer	799 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.030
Graphite monochromator	θmax = 25.0°, θmin = 2.1°
2θ/θ scans	h = −8→8
Absorption correction: analytical (SHELXS97; Sheldrick, 1997a)	k = −8→8
Tmin = 0.958, Tmax = 0.989	l = −23→23
2100 measured reflections	3 standard reflections every 97 reflections
1050 independent reflections	intensity decay: variation <1.6%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.038	H-atom parameters constrained
wR(F^2) = 0.082	w = 1/[σ^2(Fo^2) + (0.0322P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.06	(Δ/σ)max < 0.001
1050 reflections	Δρmax = 0.11 e Å^−3
119 parameters	Δρmin = −0.12 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997a), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.019 (3)

Special details

Experimental. crystal mounted on glass fiber using cyanoacrylate cement

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
O1	1.0040 (3)	0.4090 (3)	0.90047 (9)	0.0585 (6)
H1A	0.9912	0.4977	0.8764	0.070*
O2	1.0684 (3)	0.1830 (3)	0.69521 (8)	0.0566 (6)
O3	1.0882 (2)	0.2507 (3)	0.80387 (8)	0.0484 (5)
C1	0.7475 (3)	0.2602 (4)	0.83246 (12)	0.0419 (6)
H1B	0.7193	0.3849	0.8200	0.050*
C2	0.9551 (4)	0.2566 (4)	0.86408 (12)	0.0426 (7)
C3	0.9971 (4)	0.0929 (4)	0.90651 (12)	0.0457 (7)
H3A	1.1220	0.1101	0.9301	0.055*
H3B	1.0121	−0.0101	0.8771	0.055*
C4	0.8343 (4)	0.0534 (4)	0.95806 (12)	0.0471 (7)
H4A	0.8233	0.1564	0.9885	0.057*
C5	0.6370 (4)	0.0322 (4)	0.92048 (13)	0.0505 (8)
H5A	0.6461	−0.0690	0.8899	0.061*
H5B	0.5321	0.0072	0.9527	0.061*
C6	0.5847 (4)	0.2005 (4)	0.88068 (13)	0.0530 (8)
H6A	0.4643	0.1782	0.8551	0.064*
H6B	0.5573	0.2971	0.9121	0.064*
C7	0.7743 (4)	0.1558 (4)	0.76743 (13)	0.0434 (7)
H7A	0.7635	0.0277	0.7780	0.052*
C8	0.9874 (4)	0.1950 (3)	0.75016 (15)	0.0422 (6)
C9	0.6306 (4)	0.1972 (5)	0.71059 (13)	0.0688 (11)
H9A	0.4977	0.1688	0.7246	0.103*
H9B	0.6645	0.1266	0.6718	0.103*
H9C	0.6387	0.3222	0.6994	0.103*
C10	0.8832 (5)	−0.1111 (4)	0.99959 (13)	0.0633 (9)
H10A	1.0074	−0.0932	1.0224	0.095*
H10B	0.8930	−0.2136	0.9705	0.095*
H10C	0.7800	−0.1307	1.0322	0.095*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0748 (15)	0.0495 (12)	0.0512 (11)	−0.0168 (12)	−0.0101 (12)	−0.0045 (9)
O2	0.0618 (12)	0.0574 (13)	0.0507 (11)	−0.0011 (11)	0.0196 (11)	−0.0026 (10)
O3	0.0351 (9)	0.0629 (12)	0.0473 (10)	−0.0060 (10)	0.0021 (9)	0.0006 (11)
C1	0.0368 (13)	0.0463 (15)	0.0424 (13)	0.0041 (15)	−0.0036 (11)	0.0008 (15)
C2	0.0390 (15)	0.0493 (15)	0.0394 (13)	−0.0016 (15)	−0.0014 (12)	−0.0028 (15)
C3	0.0377 (15)	0.0496 (17)	0.0497 (15)	0.0021 (15)	−0.0078 (14)	−0.0037 (14)
C4	0.0518 (17)	0.0482 (17)	0.0413 (14)	0.0046 (15)	0.0004 (14)	−0.0008 (14)
C5	0.0414 (16)	0.059 (2)	0.0507 (16)	−0.0060 (16)	0.0094 (14)	0.0045 (15)
C6	0.0383 (14)	0.070 (2)	0.0509 (15)	0.0072 (16)	0.0027 (14)	−0.0014 (15)
C7	0.0382 (15)	0.0451 (15)	0.0470 (15)	−0.0017 (14)	−0.0022 (12)	−0.0024 (14)
C8	0.0431 (13)	0.0368 (15)	0.0469 (13)	0.0008 (14)	0.0040 (14)	0.0000 (12)
C9	0.0549 (17)	0.099 (3)	0.0529 (16)	−0.003 (2)	−0.0136 (15)	0.0002 (18)
C10	0.071 (2)	0.060 (2)	0.0587 (18)	0.002 (2)	−0.0054 (18)	0.0127 (16)

Geometric parameters (Å, º)

O1—C2	1.386 (3)	C4—H4A	0.9800
O1—H1A	0.8200	C5—C6	1.524 (4)
O2—C8	1.221 (3)	C5—H5A	0.9700
O3—C8	1.329 (3)	C5—H5B	0.9700
O3—C2	1.493 (3)	C6—H6A	0.9700
C1—C7	1.517 (4)	C6—H6B	0.9700
C1—C6	1.521 (4)	C7—C8	1.503 (4)
C1—C2	1.531 (3)	C7—C9	1.517 (4)
C1—H1B	0.9800	C7—H7A	0.9800
C2—C3	1.509 (4)	C9—H9A	0.9600
C3—C4	1.527 (3)	C9—H9B	0.9600
C3—H3A	0.9700	C9—H9C	0.9600
C3—H3B	0.9700	C10—H10A	0.9600
C4—C10	1.513 (4)	C10—H10B	0.9600
C4—C5	1.531 (4)	C10—H10C	0.9600
C2—O1—H1A	109.5	C4—C5—H5B	109.3
C8—O3—C2	110.10 (19)	H5A—C5—H5B	108.0
C7—C1—C6	118.0 (2)	C1—C6—C5	113.6 (2)
C7—C1—C2	103.32 (19)	C1—C6—H6A	108.8
C6—C1—C2	113.23 (19)	C5—C6—H6A	108.8
C7—C1—H1B	107.2	C1—C6—H6B	108.8
C6—C1—H1B	107.2	C5—C6—H6B	108.8
C2—C1—H1B	107.2	H6A—C6—H6B	107.7
O1—C2—O3	107.3 (2)	C8—C7—C9	113.5 (2)
O1—C2—C3	109.16 (18)	C8—C7—C1	102.0 (2)
O3—C2—C3	108.1 (2)	C9—C7—C1	116.8 (2)
O1—C2—C1	114.5 (2)	C8—C7—H7A	108.0
O3—C2—C1	102.73 (17)	C9—C7—H7A	108.0
C3—C2—C1	114.4 (2)	C1—C7—H7A	108.0
C2—C3—C4	113.3 (2)	O2—C8—O3	120.7 (3)
C2—C3—H3A	108.9	O2—C8—C7	127.9 (3)
C4—C3—H3A	108.9	O3—C8—C7	111.4 (2)
C2—C3—H3B	108.9	C7—C9—H9A	109.5
C4—C3—H3B	108.9	C7—C9—H9B	109.5
H3A—C3—H3B	107.7	H9A—C9—H9B	109.5
C10—C4—C3	111.4 (2)	C7—C9—H9C	109.5
C10—C4—C5	111.7 (2)	H9A—C9—H9C	109.5
C3—C4—C5	108.4 (2)	H9B—C9—H9C	109.5
C10—C4—H4A	108.4	C4—C10—H10A	109.5
C3—C4—H4A	108.4	C4—C10—H10B	109.5
C5—C4—H4A	108.4	H10A—C10—H10B	109.5
C6—C5—C4	111.6 (2)	C4—C10—H10C	109.5
C6—C5—H5A	109.3	H10A—C10—H10C	109.5
C4—C5—H5A	109.3	H10B—C10—H10C	109.5
C6—C5—H5B	109.3
C8—O3—C2—O1	−140.5 (2)	C3—C4—C5—C6	−58.9 (3)
C8—O3—C2—C3	101.9 (2)	C7—C1—C6—C5	75.8 (3)
C8—O3—C2—C1	−19.4 (3)	C2—C1—C6—C5	−45.0 (3)
C7—C1—C2—O1	146.7 (2)	C4—C5—C6—C1	54.4 (3)
C6—C1—C2—O1	−84.5 (3)	C6—C1—C7—C8	−156.2 (2)
C7—C1—C2—O3	30.6 (3)	C2—C1—C7—C8	−30.4 (3)
C6—C1—C2—O3	159.5 (2)	C6—C1—C7—C9	79.4 (3)
C7—C1—C2—C3	−86.2 (3)	C2—C1—C7—C9	−154.8 (2)
C6—C1—C2—C3	42.6 (3)	C2—O3—C8—O2	179.0 (2)
O1—C2—C3—C4	80.1 (3)	C2—O3—C8—C7	−0.2 (3)
O3—C2—C3—C4	−163.5 (2)	C9—C7—C8—O2	−32.7 (4)
C1—C2—C3—C4	−49.8 (3)	C1—C7—C8—O2	−159.2 (3)
C2—C3—C4—C10	−179.7 (2)	C9—C7—C8—O3	146.5 (3)
C2—C3—C4—C5	56.9 (3)	C1—C7—C8—O3	19.9 (3)
C10—C4—C5—C6	178.0 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1A···O2^i	0.82	2.02	2.830 (3)	169
C1—H1B···O2^i	0.98	2.66	3.430 (4)	136

Symmetry code: (i) −x+2, y+1/2, −z+3/2.