16-O-Methyl­cafestol

Xia-Li Liao; Xiao-Zhen Chen; Kai-Bei Yu; Guo-You Li

doi:10.1107/S1600536810007920

. 2010 Mar 6;66(Pt 4):o760. doi: 10.1107/S1600536810007920

16-O-Methylcafestol

Xia-Li Liao ^a, Xiao-Zhen Chen ^a, Kai-Bei Yu ^b, Guo-You Li ^a,^*

PMCID: PMC2983991 PMID: 21580605

Abstract

The title compound [systematic name: (3bS,5aS,7R,8R,10aR,10bS)-7-methoxy-10b-methyl-3b,4,5,6,7,8,9,10,10a,10b,11,12-dodecahydro-5a,8-methano-5aH-cycloheptal[5,6]naphtho[2,1-b]furan-7-methanol], C₂₁H₃₀O₃, was isolated from the beans of Coffea robusta. The molecule contains five fused rings including a furan ring. The two six-membered rings are in chair conformations, but the third six-membered ring and the five-membered aliphatic ring adopt envelope conformations. Intermolecular O—H⋯O hydrogen bonding is present in the crystal structure.

Related literature

For related structures, see: Beattie & Mills (1955 ▶); Djerassi et al. (1959 ▶); Finnegan & Djerassi (1960 ▶); Scott et al. (1962 ▶); Ducruix et al. (1977 ▶); Chakrabarti & Venkatesan (1981 ▶). For a total synthesis of cafestol, see: Corey et al. (1987 ▶). For the absolute configuration of a related compound, see: Djerassi et al. (1953 ▶). For the relative configuration, see: Scharnhop & Winterhalter (2009 ▶).

Experimental

Crystal data

C₂₁H₃₀O₃
M _r = 330.45
Monoclinic,
a = 10.6399 (9) Å
b = 7.0001 (5) Å
c = 11.5765 (12) Å
β = 92.640 (5)°
V = 861.31 (13) Å³
Z = 2
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 93 K
0.50 × 0.33 × 0.20 mm

Data collection

Rigaku SPIDER diffractometer
6921 measured reflections
2116 independent reflections
1961 reflections with I > 2σ(I)
R _int = 0.029

Refinement

R[F ² > 2σ(F ²)] = 0.031
wR(F ²) = 0.069
S = 1.00
2116 reflections
223 parameters
1 restraint
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.22 e Å⁻³
Δρ_min = −0.15 e Å⁻³

Data collection: RAPID-AUTO (Rigaku, 2004 ▶); cell refinement: RAPID-AUTO; data reduction: RAPID-AUTO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810007920/xu2727sup1.cif

e-66-0o760-sup1.cif^{(23KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810007920/xu2727Isup2.hkl

e-66-0o760-Isup2.hkl^{(104KB, 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—H3O⋯O2ⁱ	0.81 (3)	1.97 (3)	2.7479 (19)	163 (3)

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Symmetry code: (i) Inline graphic .

Acknowledgments

The authors are grateful to the analytical staff of Chengdu Institute of Biology, CAS, for measuring the NMR spectra.

supplementary crystallographic information

Comment

Coffea robusta is a species of coffee which has its origins in western Africa. As a part of our research on the bioactive constituents in coffee, the title compound was isolated. Its relative configuration was obtained from ESI-MS and NMR analyses, which were compared with a recent report (Scharnhop et al., 2009), and confirmed by Single-crystal X-ray diffraction study. The molecule of the title compound contains a five-ring system A/B/C/D/E(Fig. 1). There is a trans junction between ring A(C1—C5/C10)and ring B(C5—C10). Cis junction are present between ring B and ring C(C8—C9/C11—C14) and ring C and ring D(C8/C13—C16). Ring A and D are both in envelope-like conformations, with C10 and C16 at the flap, respectively. Ring B and C both adopt chair conformations. The furan ring E(C5—C6/C18—C19/O1), of course, is planar. Intermolecular O—H···O hydrogen bonding helps to stabilize the crystal structure(Fig. 2).

Experimental

The powdered seeds of Coffea robusta were extracted with cyclohexane and filtered. The filtrate was evaporated under reduced pressure. Then the residue was hydrolyzed with KOH in EtOH and extracted with tert-Butyl methyl ether(TBME). The extract was chromatograhed over Silica gel column with eluent of petroleum ether/ethyl acetate(3:1) to provide the title compound as white solid. It was recrystallized in acetone to afford suitable crystals for Single-crystal X-ray diffraction analysis.