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Molecular and crystalline structures of (s)-4-decyloxycarbonyl-2-azetidinone and (s)-4-hexadecyloxycarbonyl-2-azetidinone

Luis E. Seijas 1Asiloé J. Mora 1Andy Fitch 2Michela Brunelli 3Francisco López Carrasquero 4

1. Universidad de Los Andes, Facultad de Ciencias, Laboratorio de Cristalografía, Merida 5101, Venezuela
2. European Synchrotron Radiation Facility (ESRF), Grenoble 38043, France
3. Europen Synchrotron Radiation Facility (ESRF), 6, Jules Horowitz, Grenoble 38000, France
4. Universidad de Los Andes, Facultad de Ciencias, Laboratorio de Polímeros, Merida 5101, Venezuela


The compounds (S)-4-decyloxycarbonyl-2-azetidinone (I) and (S)-4-hexadecyloxycarbonyl-2-azetidinone (II) are optically active b-lactam derivatives of aspartic acid, which  are used as starting materials in anionic polymerization to produce poly-b-peptides[1]. These polymers adopt conformations that resemble those of the a-helixes and display properties of liquid crystals and piezoelectricity [2-4]. In this work the structures of these (S)-4-alkoxycarbonyl-2-azetidinones were solved by means of the parallel tempering algorithm implemented in the program FOX [5].  Both compounds crystallize in monoclinic cells P21, with cell parameters a= 27.81703(3) Å, b= 5.35138(4) Å, c=5.35138(4) Å, b=92.046(1)º (compound I); and a=37.14982(7) Å, b=5.35795(6) Å, c=5.30862(1) Å, b=92.169(1)º (compound II). During the Rietveld refinement [6] with the program GSAS [7], bond distances and angles were restrained to vary within ±0.02 Ǻ and ±1.5º, respectively. Both compounds display a similar asymmetry pattern in the distances of the azedinone ring and deviation from planarity due to the presence in the ring of different hydration states of the carbons atoms. The aliphatic chain presents normal bond distances and angles for sp3 carbon atoms, and torsion angles close to 180º. The crystal packing is dominated by hydrogen bonds of the type N—H···O, which form extended chains running along b and described by the first order graph symbol C(4); additionally, van der Waals interactions between neighboring aliphatic chains help to form supramolecular zig-zag structures.

Acknowledgement: This study was supported by the CDCHT-ULA, FONACIT-Venezuela (Lab-97000821) and beam line ID31, ESRF (France).


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  6. Von Dreele R. B. & Larson A. C. (2007). GSAS: General Structure Analysis System. Los Alamos National Laboratory, Los Alamos, New Mexico, USA.

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Presentation: Poster at 11th European Powder Diffraction Conference, Poster session, by Luis E. Seijas
See On-line Journal of 11th European Powder Diffraction Conference

Submitted: 2008-05-01 01:05
Revised:   2009-06-07 00:48