Absolute configuration of fibaruretin B

Hoong-Kun Fun; Abdul Wahab Salae; Ibrahim Abdul Razak; Melati Khairuddean; Suchada Chantrapromma

doi:10.1107/S1600536811014887

. 2011 Apr 29;67(Pt 5):o1246–o1247. doi: 10.1107/S1600536811014887

Absolute configuration of fibaruretin B

Hoong-Kun Fun ^a,^*,^‡, Abdul Wahab Salae ^a,^§, Ibrahim Abdul Razak ^a, Melati Khairuddean ^b, Suchada Chantrapromma ^c,^¶

PMCID: PMC3089215 PMID: 21754539

Abstract

The title furanoditerpenoid, known as fibaruretin B (systematic name: 2β,3α-dihydroxy-2,3,7,8α-tetrahydropenianthic acid lactone), C₂₀H₂₄O₇, was isolated from the roots of Arcangelisia flava. The absolute configurations at positions 2, 3, 4, 4a, 7, 9, 10a and 10b of fibaruretin B are S, R, S, R, S, S, S and S, respectively. In the crystal structure, the molecules are linked into infinite chains along the c axis by O—H⋯O hydrogen bonds and weak C—H⋯O interactions.

Related literature

For ring conformations, see: Cremer & Pople (1975 ▶). For bond-length data, see: Allen et al. (1987 ▶). For background to and activities of furanoditerpenoids, see: Ito & Furukawa (1969 ▶); Keawpradub et al. (2005 ▶); Moody et al. (2006 ▶); Nguyen-Pouplin et al. (2007 ▶); Su et al. (2008 ▶). For a related structure, see: Bakhari et al. (1998 ▶). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986 ▶).

Experimental

Crystal data

C₂₀H₂₄O₇
M _r = 376.39
Monoclinic,
a = 7.0942 (2) Å
b = 11.7149 (4) Å
c = 10.1921 (3) Å
β = 90.805 (1)°
V = 846.96 (5) Å³
Z = 2
Cu Kα radiation
μ = 0.93 mm⁻¹
T = 100 K
0.43 × 0.12 × 0.08 mm

Data collection

Bruker APEX DUO CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009 ▶) T _min = 0.692, T _max = 0.926
11247 measured reflections
2645 independent reflections
2641 reflections with I > 2σ(I)
R _int = 0.018

Refinement

R[F ² > 2σ(F ²)] = 0.025
wR(F ²) = 0.066
S = 1.09
2645 reflections
254 parameters
1 restraint
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.19 e Å⁻³
Δρ_min = −0.15 e Å⁻³
Absolute structure: Flack (1983 ▶), with 1098 Friedel pairs
Flack parameter: 0.03 (12)

Data collection: APEX2 (Bruker, 2009 ▶); cell refinement: SAINT (Bruker, 2009 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536811014887/is2703sup1.cif

e-67-o1246-sup1.cif^{(23.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536811014887/is2703Isup2.hkl

e-67-o1246-Isup2.hkl^{(129.9KB, 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
O3—H1O3⋯O5ⁱ	0.86 (3)	2.54 (3)	3.1305 (15)	127 (2)
O4—H1O4⋯O6ⁱ	0.87 (3)	2.12 (3)	2.9708 (14)	165 (2)
C3—H3A⋯O5ⁱ	0.98	2.39	3.1295 (16)	131
C6—H6A⋯O2	0.97	2.43	3.1718 (19)	133
C8—H8A⋯O2ⁱⁱ	0.98	2.29	3.2113 (19)	157
C19—H19C⋯O3	0.96	2.31	2.9489 (18)	124
C20—H20B⋯O7ⁱⁱⁱ	0.96	2.53	3.4613 (18)	164

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

Acknowledgments

AWS thanks the Universiti Sains Malaysia for a PhD Student Visiting Fellowship. SC thanks the Prince of Songkla University for financial support through the Crystal Materials Research Unit. The authors thank the Universiti Sains Malaysia for Research University Grant No. 1001/PFIZIK/811151.

supplementary crystallographic information

Comment

Furanoditerpenoids are secondary metabolites which were found in Menispermaceae plants such as Fibraurea chloroleuta Miers (Ito & Furukawa, 1969), Fibraurea tinctoria Lour. (Su et al., 2008) and Sphenocentrum jollyanum Pierre (Moody et al., 2006). They were found to possess biological properties such as anti-inflammatory and antimalarial activities. Arcangelisia flava (Menispermaceae), commonly called `Khaminkhruea' in the southern Thailand, is widely distributed from Hainan (China), Indo-China, southern peninsular Thailand, peninsular Malaysia, Sumatra, Java, Borneo, the Philipines, Sulawesi, the Northern Moluccas to New Guinea. It is an available medicinal plant used for the treatment of malaria, dysentery and as a tonic. The antimalarial, cytotoxic and antioxidant effects of this plant have been reported (Nguyen-Pouplin et al., 2007; Keawpradub et al., 2005). During the course of our study of bioactive compounds from medicinal plants, the title furanoditerpenoid compound, (I), which is known as fibaruretin B, was isolated for the first time from the roots of Arcangelisia flava (Menispermaceae) which were collected from Songkhla province in the southern part of Thailand. The absolute configuration of (I) was determined by making use of the anomalous scattering of Cu Kα radiation with the Flack parameter being refined to 0.03 (12).

The molecule of (I) has four fused rings consisting of one five- and three six-membered rings (A/B/C/D) (Fig. 1). The two cyclohexane rings A and B are cis fused, whereas the cyclohexane ring B and pyran ring C are trans fused. The cyclohexane ring A (C1–C5/C10) is in an envelope conformation, with the pucker atom C3 (0.4436 (16) Å) and puckering parameter Q = 0.6349 (16) Å, θ = 46.82 (14)° and φ = 115.0 (2)° (Cremer & Pople, 1975). The cyclohexane ring B (C5–C10) adopts a twisted boat conformation with puckering parameter Q = 0.7098 (15) Å, θ = 99.25 (12)° and φ = 45.65 (13)°. The pyran ring C (O5/C17/C8/C9/C11/C12) is in a boat conformation with puckering parameter Q = 0.7026 (15) Å, θ = 89.67 (12)° and φ = 241.68 (12)°. The tetrahydrofuran ring D (O1/C2–C4/C18) is in an envelope conformation, with the pucker atom C3 [-0.2883 (16) Å] and puckering parameter Q = 0.4584 (16) Å and φ = 258.04 (19)°. The furan ring (C13–C16/O7) is planar with an r.m.s. 0.0028 (2) Å and is equatorially attached to the pyran ring C with torsion angles O5—C12—C13—C14 = -76.91 (15)° and O5—C12—C13—C16 = 105.01 (16)°. The bond distances in (I) are within normal ranges (Allen et al., 1987) and comparable with the related structure (Bakhari et al., 1998).

The absolute configuration at atoms C2, C3, C4, C5, C8, C12, C9, C10 or positions 2, 3, 4, 4a, 7, 9, 10a and 10b of the fibaruretin B are S, R, S, R, S, S, S and S, respectively which agree with the previous stereochemistry of fibaruretin B (Su et al., 2008).

In the crystal packing of (I) (Fig. 2), the molecules are linked into chains along the c axis through O—H···O hydrogen bonds and C—H···O weak interactions (Fig. 2 and Table 1) and the crystal is stabilized by these interactions.

Experimental

The air-dried roots of Arcangelisia flava (Menispermaceae) (1.8 kg) were extracted with CH₂Cl₂ (2 × 10 l) under room temperature. The combined extracts were concentrated under reduced pressure to give a yellow extract (30.1 g) which was subjected to quick column chromatography over silica gel using solvents of increasing polarity from n-hexane to EtOAc to afford 10 fractions (F1–F10). Fraction F9 was further purified by column chromatography using CH₂Cl₂–EtOAc (6:4), yielding the title compound as a white solid (275.3 mg). Colorless needle-shaped single crystals of the title compound suitable for X-ray structure determination were recrystallized from CH₂Cl₂ by the slow evaporation of the solvent at room temperature after several days (m.p. 539–540 K).