4′,5-Dihy­droxy-7-meth­oxy­flavanone dihydrate

Iván Brito; Jorge Bórquez; Mario Simirgiotis; Alejandro Cárdenas; Matías López-Rodríguez

doi:10.1107/S1600536811051221

. 2011 Dec 7;68(Pt 1):o32–o33. doi: 10.1107/S1600536811051221

4′,5-Dihydroxy-7-methoxyflavanone dihydrate

Iván Brito ^a,^*, Jorge Bórquez ^a, Mario Simirgiotis ^a, Alejandro Cárdenas ^b, Matías López-Rodríguez ^c

PMCID: PMC3254395 PMID: 22259537

Abstract

The title compound, C₁₆H₁₄O₅·2H₂O [systematic name: 5-hydroxy-2-(4-hydroxyphenyl)-7-methoxychroman-4-one dihydrate], is a natural phytoalexin flavone isolated from the native chilean species Heliotropium taltalense and crystallizes with an organic molecule and two water molecules in the asymmetric unit. The 5-hydroxy group forms a strong intramolecular hydrogen bond with the carbonyl group, resulting in a six-membered ring. In the crystal, the components are linked by O—H⋯O hydrogen bonds, forming a three-dimensional network. The 4-hydroxyphenyl benzene ring is bonded equatorially to the pyrone ring, which adopts a slightly distorted sofa conformation. The title compound is the hydrated form of a previously reported structure [Shoja (1990 ▶). Acta Cryst. C46, 1969–1971]. There are only slight variations in the molecular geometry between the two compounds.

Related literature

For the first study of the title compound, see: Narasimhachari & Seshadri (1949 ▶); Atkinson & Blakeman (1982 ▶). For its biological properties, see: Plowright et al. (1996 ▶); Atkinson & Blakeman (1982 ▶), Saito et al. (2008 ▶). For its spectroscopic properties, see: Agrawal (1989 ▶); Ogawa et al. (2007 ▶). For the structure of the unsolvated compound, see: Shoja (1990 ▶). For similar compounds, see: Modak et al. (2009 ▶). For graph-set notation, see: Bernstein et al. (1995 ▶). For puckering parameters, see: Cremer & Pople (1975 ▶). For molecular geometry calculations, see: Macrae et al. (2008 ▶).

Experimental

Crystal data

C₁₆H₁₄O₅·2H₂O
M _r = 322.30
Orthorhombic,
a = 5.0869 (10) Å
b = 9.4622 (19) Å
c = 32.318 (7) Å
V = 1555.6 (5) Å³
Z = 4
Mo Kα radiation
μ = 0.11 mm⁻¹
T = 293 K
0.20 × 0.15 × 0.03 mm

Data collection

Nonius KappaCCD area-detector diffractometer
9743 measured reflections
2021 independent reflections
1623 reflections with I > 2σ(I)
R _int = 0.068

Refinement

R[F ² > 2σ(F ²)] = 0.075
wR(F ²) = 0.180
S = 1.17
2021 reflections
224 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.38 e Å⁻³
Δρ_min = −0.29 e Å⁻³

Data collection: COLLECT (Nonius, 2000 ▶; cell refinement: DENZO-SMN (Otwinowski & Minor, 1997 ▶); data reduction: DENZO-SMN; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: PLATON (Spek, 2009 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶) and publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811051221/kj2193sup1.cif

e-68-00o32-sup1.cif^{(19.1KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811051221/kj2193Isup2.hkl

e-68-00o32-Isup2.hkl^{(97.4KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536811051221/kj2193Isup3.cml

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
O3—H3⋯O2	0.82	1.90	2.630 (5)	147
O5—H5⋯O7	0.76 (9)	1.99 (9)	2.720 (7)	163 (7)
O6—H6A⋯O2ⁱ	0.87 (9)	2.00 (8)	2.847 (6)	166 (7)
O6—H6B⋯O3ⁱⁱ	0.81 (6)	2.11 (6)	2.915 (5)	174 (8)
O7—H7A⋯O5ⁱ	0.85	2.27	3.055 (7)	153
O7—H7B⋯O6ⁱⁱⁱ	0.85	1.94	2.763 (6)	163

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) .

Acknowledgments

IB thanks the Spanish Research Council (CSIC) for providing us with a free-of-charge licence for the CSD system. The authors acknowdledge funds from FONDECYT (1110068) and U. Antofagasta (CODEI N° 1383).

supplementary crystallographic information

Comment

The crystal structure of the flavanone (S)-sakuranetin (5,4'-di-hydroxy-7-methoxyflavanone dihydrate, C₁₆H₁₄O₅.2H₂O) which was isolated from the native Chilean shrub Heliotropium taltalense (Heliotropiaceae) collected in Quebrada de Paposo II Region of Chile, is presented in this paper. (S)-Sakuranetin is a methylated flavanone obtained from the bark of Prunuspuddum (Narasimhachari & Seshadri, 1949) and later from other Prunus species (Atkinson & Blakeman, 1982). This compound is a phytoalexin produced in response to infection in rice (Plowright et al., 1996) with several beneficial biological properties such as antimicrobial activity (Atkinson & Blakeman, 1982) and the induction of adipogenesis (Saito et al., 2008). H. taltalense, is an endemic shrub or bush that grows in arid regions which obtains survival water from condensation from the Chilean coastal fog. Several Heliotropium species grow freely mainly in the north of Chile and they have glandular secreting trichomes whose principal rol is to produce a gummy exudate aimed to protect the plant from environmental factors and predators. This exudate is composed mainly of waxes and a mixture of phenolic compounds, mainly flavonoids and aromatic geranyl derivatives (Modak et al., 2009). The title compound (Fig. 1) crystallizes with an organic molecule and two water molecules in the asymmetric unit. The hydroxy group at C5 forms a strong intramolecular hydrogen bond with the carbonyl group with graph-set notation S(6) (Bernstein, et al., 1995). This interaction is observed in the unsolvated compound too, (Shoja, 1990). In the crystal, the components are linked by intermolecular O—H···O hydrogen bonds with an average O···O distance of 2.86 (14) Å and O—H···O angles in the range 147–174°, forming a 3-D network (Fig. 2). The 4'-hydroxyphenyl ring is bonded equatorially to the pyrone ring which adopts a slightly distorted sofa conformation with the C2 atom 0.328 (5) Å out of plane defined by the C2/C3/C4/C9/C10/O1 atoms, [puckering amplitude Q_T= 0.465 (5) Å; θ =124.9 (6)° & φ = 245.3 (7)° (Cremer & Pople, 1975)]. The title compound is the hydrated form of a previously reported structure. There are only slight variations in the molecular geometry of both compounds, so when both compound are superimposed all atoms are fitted within RMSD 0.0715 Å, (with inversion & flexibility), (Macrae et al., 2008), as is shown in Fig. 3.

Experimental

Dried aerial parts of H. taltalense (1.8 kg) were immersed in ethyl acetate (EtOAc) for one minute (2 l) in order to obtain an extract from the exudate. The extract was immediately concentrated in vacuo and the resulting dark brown syrup (47 g) was adsorbed on to silicagel 60 G (50 g) and slurred onto the top of a column containing silica gel 60 H (0.5 kg), partitioned using a medium pressure pump with an isocratic eluent (n-hexane–EtOAc 8:2), to obtain six partitions (fractions A to F: n-hexane, n-hexane–EtOAc 95:5, n-hexane–EtOAc 90:10, n-hexane–EtOAc 80:20, n-hexane–EtOAc 50:50 and pure EtOAc). Further purification by a combination of chromatography on silicagel 60 H and permeation through Sephadex LH-20 (eluting with methanol-water 7:3) of the fraction 20% hexane-ethyl acetate (fraction D, 15 g) afforded the phytoalexin 5,4'-di-hydroxy-7-methoxyflavanone dihydrate for which 1-D and 2-D NMR data are consistent with literature (Agrawal, 1989; Ogawa, et al., 2007). Recrystallization from hexane-ethyl acetate (9:1) at -20 ° C yielded yellow crystals of (S)-sakuranetin dihydrate (0.039 g), suitable for X-ray diffraction analysis.