2-Hydr­oxy-6,6-dimethyl­bicyclo­[3.1.1]heptane-2-carboxylic acid

Yan-Qing Gao; Shi-Bin Shang; Xu Xu; Xiao-Ping Rao; Hong-Xiao Wang

doi:10.1107/S1600536809041385

. 2009 Oct 17;65(Pt 11):o2748. doi: 10.1107/S1600536809041385

2-Hydroxy-6,6-dimethylbicyclo[3.1.1]heptane-2-carboxylic acid

Yan-Qing Gao ^a, Shi-Bin Shang ^a,^*, Xu Xu ^a, Xiao-Ping Rao ^a, Hong-Xiao Wang ^a

PMCID: PMC2971213 PMID: 21578342

Abstract

The title compound, C₁₀H₁₆O₃, with a bicyclo[3.1.1]heptane unit, was obtained by oxidation of β-pinene. The asymmetric unit contains two independent molecules with similar geometry: the six-membered rings in both molecules adopt envelope conformations. In the crystal, the independent molecules exist as O—H⋯O hydrogen-bonded dimers. The dimers are linked into helical chains along the b axis by O—H⋯O hydrogen bonds.

Related literature

For the preparation of nopinone and nopinic acid, see: Winstein & Holness (1955 ▶); Ma et al. (2007 ▶). For the crystal structure of sodium nopinate [sodium (1R,2S,5S)-2-hydroxy-6,6-dimethylbicyclo[3.1.1]heptane-2-carboxylate pentahydrate], see: Ma et al. (2008 ▶).

Experimental

Crystal data

C₁₀H₁₆O₃
M _r = 184.23
Monoclinic,
a = 26.796 (5) Å
b = 6.6560 (13) Å
c = 12.250 (3) Å
β = 112.23 (3)°
V = 2022.5 (9) Å³
Z = 8
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 293 K
0.30 × 0.20 × 0.20 mm

Data collection

Enraf–Nonius CAD-4 diffractometer
Absorption correction: ψ scan (XCAD4; Harms & Wocadlo, 1995 ▶) T _min = 0.974, T _max = 0.983
2047 measured reflections
2002 independent reflections
1565 reflections with I > 2σ(I)
R _int = 0.018
3 standard reflections every 200 reflections intensity decay: 1%

Refinement

R[F ² > 2σ(F ²)] = 0.056
wR(F ²) = 0.153
S = 1.00
2002 reflections
242 parameters
3 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.21 e Å⁻³
Δρ_min = −0.23 e Å⁻³

Data collection: CAD-4 Software (Enraf–Nonius, 1989 ▶); cell refinement: CAD-4 Software; data reduction: XCAD4 (Harms & Wocadlo, 1995 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809041385/ci2928sup1.cif

e-65-o2748-sup1.cif^{(23.2KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809041385/ci2928Isup2.hkl

e-65-o2748-Isup2.hkl^{(98.5KB, hkl)}

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

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1A⋯O2	0.81 (3)	2.38 (8)	2.837 (5)	116 (7)
O2—H2D⋯O6	0.82	1.80	2.621 (5)	175
O4—H4C⋯O1ⁱ	0.84 (5)	2.05 (5)	2.830 (5)	156 (5)
O5—H5C⋯O3	0.82	1.88	2.704 (4)	177

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Symmetry code: (i) Inline graphic .

supplementary crystallographic information

Comment

Terpenes are convenient chiral precursors due to their availability and low cost, and among them β-pinene is an important material. Many valuable chemicals were prepared from β-pinene. For instance, nopinone (Winstein & Holness, 1955) and nopinic acid were prepared by oxidation of β-pinene. Although the title compound has been prepared (Ma et al., 2007) and the crystal structure of sodium nopinate has been reported (Ma et al., 2008), the crystal structure of nopinic acid has not been reported. In this paper, we report the crystal structure of the title compound.

The asymmetric unit contains two crystallographically independent molecules (Fig. 1) with similar geometry. The six-membered rings in both the molecules adopt envelope conformations. The independent molecules are linked through a pair of O–H···O hydrogen bonds (Table 1) forming a dimer. The dimers are linked into helical chains along the b axis (Fig. 2) by O—H···O hydrogen bonds.

Experimental

Potassium permanganate (12.0 g) and NaOH (1.5 g) were dissolved in the mixture of water (100 ml) and t-butylalcohol (50 ml). While stirring vigorously, pure (-)-beta-pinene (5.2 g) was added. The reaction was maintained at the temperature of 288–298 K for 0.5 h. The mixture was heated to 353 K, then filtered and the precipitate was washed with hot water. After standing for 12 h at 273 K, sodium nopinate was filtered. The crude sodium nopinate was acidified with dilute hydrochloric acid and extracted with dichloromethane, then the product, crude nopinic acid was obtained. The crude nopinic acid was recrystallized from toluene. Single crystals of the title compound suitable for X-ray diffraction were obtained by slow evaporation of a ethanol-toluene solution.