Preaustinoid A: a meroterpene produced by Penicillium sp

Stella H Maganhi; Taicia Pacheco Fill; Edson Rodrigues-Fo; Ignez Caracelli; Julio Zukerman-Schpector

doi:10.1107/S1600536808043481

. 2009 Jan 8;65(Pt 2):o221. doi: 10.1107/S1600536808043481

Preaustinoid A: a meroterpene produced by Penicillium sp.

Stella H Maganhi ^a, Taicia Pacheco Fill ^a, Edson Rodrigues-Fo ^a, Ignez Caracelli ^b, Julio Zukerman-Schpector ^a,^*

PMCID: PMC2968271 PMID: 21581839

Abstract

The title meroterpene preaustinoid A (systematic name: methyl 15-hydroxy-2,6,6,10,13,15-hexamethyl-17-methylene-7,14,16-trioxotetracyclo[11.3.1.0^2,11.0^5,10]heptadecane-1-carboxylate), C₂₆H₃₆O₆, features a fused four-ring arrangement. Three rings are in different distorted chair conformations and the other is in a distorted boat conformation. The absolute configuration was established based on [α_D] = −4.97° (c = 1.10 g l⁻¹, CH₂Cl₂). In the crystal, the molecules are connected into supramolecular chains via O—H⋯O hydrogen bonds.

Related literature

For related literature, see: dos Santos & Rodrigues-Fo (2002 ▶). For structure analysis, see: Cremer and Pople (1975 ▶); Iulek and Zukerman-Schpector (1997 ▶)).

Experimental

Crystal data

C₂₆H₃₆O₆
M _r = 444.55
Orthorhombic,
a = 8.5023 (2) Å
b = 13.5405 (2) Å
c = 19.7127 (4) Å
V = 2269.43 (8) Å³
Z = 4
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 290 (2) K
0.37 × 0.28 × 0.11 mm

Data collection

Bruker APEXII CCD area-detector diffractometer
Absorption correction: none
27134 measured reflections
2938 independent reflections
2677 reflections with I > 2σ(I)
R _int = 0.034

Refinement

R[F ² > 2σ(F ²)] = 0.036
wR(F ²) = 0.093
S = 1.03
2938 reflections
297 parameters
H-atom parameters constrained
Δρ_max = 0.22 e Å⁻³
Δρ_min = −0.13 e Å⁻³

Data collection: APEX2, COSMO and BIS (Bruker, 2006 ▶); cell refinement: SAINT (Bruker, 2006 ▶); data reduction: SAINT; program(s) used to solve structure: SIR97 (Altomare et al., 1999 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 (Farrugia, 1997 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808043481/tk2346sup1.cif

e-65-0o221-sup1.cif^{(26.7KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808043481/tk2346Isup2.hkl

e-65-0o221-Isup2.hkl^{(141.3KB, 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
O5—H1O5⋯O3ⁱ	0.82	2.05	2.870 (2)	173

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Symmetry code: (i) Inline graphic .

Acknowledgments

We thank FAPESP, CNPq and CAPES for financial support. Professor R. A. Burrow of the Federal University of Santa Maria is gratefully acknowledged for helping with the collection of the intensity data.

supplementary crystallographic information

Comment

Endophytic fungi have been a rich source of important biologically active secondary metabolites, in particular meroterpenoids, a class of complex metabolites derived from a mixed terpenoid-polyketide biosynthetic pathway. During an on-going study of substances produced by endophytic fungi, the title compound (I) was isolated and its structure postulated based on APCIMS (Atmospheric Pressure Chemical Ionization Mass Spectrometry), HREIMS (High Resolution Electrospray Mass Spectrometry) and a variety of NMR studies (dos Santos and Rodrigues-Fo, 2002). As suitable crystals were subsequently obtained, a crystal structure determination was undertaken. The four fused rings are in different distorted conformations. Rings A and C are distorted towards a half-chair conformation, ring B is distorted towards a half-boat conformation, and ring D is a boat conformation that is highly distorted towards a half-boat. The ring-puckering parameters (Cremer & Pople, 1975, Iulek & Zukerman-Shpector, 1997) for rings A,B,C, D are: q₂ = 0.062 (2), 0.093 (2), 0.059 (2), 0.582 (2) Å, q₃ = -0.524 (2), 0.577 (2), -0.624 (2), -0.139 (2) Å, Q = 0.528 (2), 0.584 (2), 0.627 (2), 0.599 (2)°, φ₂ = 90 (2), 172 (1), -149 (2), -122.4 (2)°, and θ₂ = 173.3 (2), 9.1 (2), 174.6 (2), 103.4 (2)°, respectively. The absolute configuration was established based on the [α_D] = -4.97° (c 1.10 g/L, CH₂Cl₂) and the results reported in dos Santos & Rodrigues-Fo (2002). The molecules are linked into a supramolecular chain via intermolecular O-H···O hydrogen bonds, Table 1.

Experimental

Compound (I), Preaustinoid A, was produced during cultivation of Penicillum sp over sterilized rice, and isolated from the methanol extract of the culture. Suitable crystals were obtained, by slow evaporation, from a mixture of dichloromethane, methanol and water.