DSpace at VNU: The crystal structure of 3-(4 '-methoxyphenyl)propanoyl pyrrole of Piper lolot C.DC from Vietnam

The title compound which was isolated from the rhizomes of Piper lolot C.DC has antibacterial activity.. The molecule consists of a planar propanoyl pyrrole and a methoxyphenyl fragment

© WILEY-VCH Verlag Berlin GmbH, 13086 Berlin, 2002 0232-1300/02/0606-0627 $ 17.50+.50/0

P.LUGER1*,M.WEBER1,N.X.DUNG2,V.T.LUU3,D.D.RANG3,D.T.TUONG3,

P.H.NGOC3

1 Institut für Chemie/Kristallographie, Freie Universität Berlin, Germany

2 Center for Education and Development of Chromatography of Vietnam and

Hanoi University of Natural Sciences

3 Hanoi Teacher's Training College and NCST of Vietnam

The Crystal Structure of 3-(4'-Methoxyphenyl)propanoyl pyrrole of Piper lolot C.DC from Vietnam

C14H15NO2 (293K): monoclinic space group P21/n, a = 24.580(10), b = 5.536(2), c = 9.037(3) Å, β = 91.18(4)°, V = 1229.4(8) Å 3 , D x = 1.239 g ⋅ cm -3 , Z = 4, F(000) = 488, λ (CuK α ) = 1.5418 Å, µ = 0.667

mm -1 The title compound which was isolated from the rhizomes of Piper lolot C.DC has antibacterial

activity Its chemical identity was established by this X-ray analysis The molecule consists of a planar propanoyl pyrrole and a methoxyphenyl fragment with an interplanar angle of 93.8(3)° which is by 30° larger than the corresponding angle reported in the literature for the comparable dimethoxy derivative,

which was also derived from Piper species

Keywords: crystal structure, piper lolot

(Received March 6, 2002; Accepted April 22, 2002)

Introduction

Pharmaceutically active compounds from domestic plants play an important role in the traditional folk medicinal system in East Asia Although the knowledge about the medicinal activity is generally based on long oral tradition from generation to generation, in several cases the chemical identity of the extracted compounds was not known, being now a challenging task for modern analytical methods The title compound was isolated from the

rhizomes of Piper lolot C.DC by extraction with n-hexane Piper lolot C.DC is known for its activity against the bacteria Bacillus pyocyaneus, Staphyloccocus aureus and B subtilis with

simultanous anti-inflamatory action It is also in use to treat various deseases like rheumatism, lumbago, digestive troubles, vomiting, diarrhoea and others (LOI, 1995;

TRUYEN & CHAU, 1999)

The genus Piper belong to the Piperaceae and has over 700 species distributed in both hemispheres The Piper species have high commercial, economical and medicinal importance Piper lolot C.DC is one species of genus Piper and reputed for its medicinal

properties in folklore medicine of Vietnam

The chemistry of Piper lolot C.DC has been investigated only on essential oil The essential oil isolated by hydro-distillation from the fresh leaves, stem and rhizomes of Piper

lolot C.DC has been analyzed for the first time by a combination of GC and GC/MS The oils

contained more than 35 compounds, of which 25 constitutes could be identified according to

* corresponding author: luger@chemie.fu-berlin.de

their chromatographic retension indices and mass spectra (DUNG,THANH,KHOI,LECLERCQ, 1996)

The lack of phytochemical investigation of the Piper lolot C.DC extract led us to this study From n-hexane extract of the rhizome of the Piper lolot C.DC, we separated two

compounds by column chromatography, one of them is β-asarone (RANG,TUONG &LUU, 2001) and the other one is this compound with MW = 229, mp 81-82°C Since its chemical indentity was originally not known, its structure was elucidated by X-ray analysis

Table 1: Crystal data, details of data collection and structure determination

Refinement (on 2146 reflections) F 2

No of reflections [F o > 2 σ (F o )] 1929

Difference electron density (eÅ -3 ) maximum 0.15

Difference electron density (eÅ -3 ) minimum -0.14

*CCDC 179879 contains the supplementary crystallographic data for this paper These data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033; or deposit@ccdc.cam.ac.uk)

Experimental

Rhizomes of Piper lolot C.DC were collected in a garden of Hanoi, Vietnam A voucher

specimen has been deposited in the Herbarium of the Institute of Ecology and Biological Resources, NCST, Hanoi, Vietnam

Rhizome of Piper lolot C.DC was washed with destilled water and dried at 60-70°C until dryness and pulverized Rhizome-powder of Piper lolot was extracted by n-hexane at room

temperature in 10 days After filtration the n-hexane extract was evaporated to dryness under reduced pressure

The mixture was chromatographied on a silicagel-column, elution was started with a mixture of n-hexane-ethylacetate with increasing polarity (from 0% to 100% ethylacetate) Pure compound was collected after re-column chromatography yielding plate shaped crystals, melting point 81-82°C, MS(m/z), MW = 229, IR cm-1 (KBr) 3153 (=NH),

3100-3000 (=CH-), 2938 ( > CH2), 2810 (-OCH3), 1715 ( > C=O), 1514-1480 (aromatic ring),

1245 (C-O)

Fig 1: ORTEP representation (J OHNSON , 1976) of the molecular structure and atom numbering scheme of the title compound, the thermal ellipsoids are drawn at a probability of 50%

A crystal with dimensions 0.46 x 0.41 x 0.11 mm was used for all X-ray investigations, which were carried out on a STOE four circle diffractometer using Ni-filtered CuKα

radiation Crystal data and details of the intensity data collection are summarized in Table 1 The unit cell constants were determined by least-squares refinement of 43 reflections in a range 30° < 2θ < 90° The repeated measurement of three standard reflections (frequency: 90 minutes) revealed no significant decay (maximum intensity variation 3%) during the data

collection The intensity data were corrected for Lorentz and polarization factors, but not for absorption The atomic scattering factors were taken from International Tables for X-ray Crystallography, Vol C

The phase problem was solved by routine application of direct methods (program SHELXS, SHELDRICK, 1986), least-squares refinements with anisotropic displacement parameters for C, N and O and isotropic displacement parameters for H (calculated from stereochemical considerations and allowed for free refinement), including an isotropic extinction parameter, were executed using SHELXL97 (SHELDRICK, 1997) Details of the refinement are included in Table 1, final atomic parameters are in Table 2, geometric parameters are in Table 3

Table 2: Fractional atomic coordinates and equivalent isotropic displacement parameters (Å 2 ) ( )1 3 * *

eq i j ij i j i j

Table 3: Selected bond lengths (Å), angles (°) and torsion angles (°)

C13-C14 1.348(2)

Results and Discussion

The molecular structure of the title compound is shown in Fig 1 along with the atomic numbering scheme The molecule consists of two almost planar structural fragments, a propanoyl pyrrole and a methoxyphenyl unit The average deviations of contribution (non H) atoms to least squares planes are 0.06 Å for the first plane and 0.009 Å for the latter one The interplanar angle is 93.8(3)°, hence the two fragments are almost perpendicular to each other

A very similar molecule, also from a Piper species (Piper brachystachyum), is reported in

the literature (KUMAR et al., 1998) 1-[3-(3,4-dimethoxyphenyl)propanoyl]pyrrole differs from the title compound only by a further methoxy group in meta position of the phenyl ring The graphical superposition (Fig 2) shows that both molecules differ by the dihedral angle

of the two major molecular planes which is 64.2(1)°, hence smaller for the dimethoxy derivative Otherwise the geometry of the two molecules is rather alike, e.g the linear chain

is in an all trans arrangement, the methoxy group(s) is(are) in plane with the phenyl ring Bond lengths and angles are as expected and need no detailed discussion Especially the values in the amide group and the double bonds in the pyrrole ring are in line with the dimethoxy derivative and a number of benzoyl and toluoyl substituted pyrrole derivatives (BENNET, SOMAYAJI, BROWN & SANTARSIERO, 1991; BEACH, BATCHELOR, EINSTEIN &

BENNET, 1998)

In the crystal lattice (see Fig 3) the molecules are in head-to-tail arrangements forming infinite chains in the ar + cr direction Neighboured molecules in a chain are connected by

the shortest intermolecular contact in this structure being a C-H O link from C12-H12 of the pyrrole ring to the methoxy O4 of a glide plane related molecule, with H O = 2.70(4)Å A second C-H O contact is C8-H82 to the carbonyl O9 of a molecule related by a translation

in br

-direction (H O = 2.71(4)Å) Further close intermolecular contacts are not observed

Fig 2: Graphical superposition of the title molecule (solid lines) and 1-(3-(3,4-dimethoxyphenyl)propanoyl)pyrrole (filled dashed lines), generated with SCHAKAL (K ELLER , 1988)

Fig 3: Illustration of the crystal packing in a projection on the ar—cr-plane H12 O4 (dashed line) is the shortest intermolecular contact (SCHAKAL drawing, K ELLER , 1988)

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