ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
P96. Application of High Resolution Mass Spectrometry to the Analysis of
Complexes of Substituted 3-(benzoxazol-5-yl)alanines with Pt(II)
A. Kluczyk, H. Bartosz-Bechowski, J. Kierzenkowska, P. Stefanowicz, K. Guzow, W. Wiczk,
Z. Szewczuk
Faculty of Chemistry, University of Wrocław, F. Joliot-Curie 14, 50-383 Wrocław, Poland,
e-mail: hbb@wchuwr.pl
The complexing properties of heterocycles are widely investigated because of the broad range of applications
found for their metal complexes, from dyes and pigments to DNA intercalators. The heterocyclic side-chains of
natural amino acids, as well as the delocalized amides in peptide backbone are responsible for the affinity of
peptides and proteins to metal ions, creating the specific activity of metalloenzymes and structural properties of
zinc fingers. Therefore the introduction of novel nonproteinaceous heterocyclic amino acids into peptides may
result in new compounds with desired structural, physicochemical and biological properties [1].
A series of 2-substituted 3-(benzoxazol-5-yl)alanines were investigated for their photochemical and biological
activity [2, 3]. It was also found that such benzoxazole derivatives substituted with 8-quinolinyl group could be
used as effective chemosensors for Zn(II), Tb(III) and Eu(III) ions [4]. It is known that 2-pyrid-2-ylbenzoxazole
forms a chelating didentate complex with Pt(II), where coordination to the metal occurs via the pyridine and ring
imine nitrogens [5]. Taking all this into account we investigated the affinity of 3-(benzoxazol-5-yl)alanines
towards Pt(II) ions, using high resolution electrospray mass spectrometry.
C
H 3
O
O
O
R
N
NH
O
O
CH 3
CH 3
CH 3
where R is:
Structures of 2-substituted 3-(benzoxazol-5-yl)alanines investigated for their affinity to Pt (II).
O
S
The mass spectra of investigated complexes revealed the differences between variously substituted benzoxazoles
in respect to their affinity to Pt(II) ions; especially the three quinoline isomers show a diversity in their relation
to the metal ion. The fragmentation experiments indicate that the binding occurs in the heterocyclic part of the
protected amino acid derivatives. The gradual changes in complex composition, as well as the differences in
stability in gas phase could be investigated and analyzed using mass spectrometry, which seems to be a method
of choice for selecting promising ligands from libraries of organic compounds.
References:
[1] A. Staszewska, P. Stefanowicz, Z. Szewczuk, Tetrahedron Lett., 46, 5525 (2005).
[2] M. Szabelski, M. Rogiewicz, W. Wiczk, Anal. Biochem. 342, 20 (2005).
[3] K. Guzow, D. Szmigiel, D. Wroblewski, M. Milewska, J. Karolczak, W. Wiczk, J. Photochem. Photobiol. A:
Chem. 187, 87 (2007).
[4] K. Guzow, M. Milewska, D. Wróblewski, A. Giełdoń, W. Wiczk, Tetrahedron, 60, 11889 (2004).
[5] X.F. He, Ch.M. Vogels, A. Decken, S.A. Westcott, Polyhedron, 23, 155 (2004).
CH 3
CH 3
N
N
H
N
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215
N
N
N