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

Eurobic9, 2-6 September, 2008, Wrocław, Poland
P160. The Peptide-heterocycle Conjugates: Derivatives of 3-(benzimidazol-
5-yl)alanine in the Presence of Selected Metal Ions
M. Ratajska, A. Kluczyk, P. Stefanowicz, H. Bartosz-Bechowski, M. Cebrat, Z. Szewczuk
Faculty of Chemistry, University of Wroclaw, F. Joliot-Curie 14, 50-383 Wroclaw, Poland,
e-mail: mkoprow@eto.wchuwr.pl
In our search for new bioactive peptides we investigate methods for introducing heterocyclic motifs into peptide
side chains [1]. Considering the biological activity and complexing abilities of benzimidazoles we developed a
direct solid-phase synthesis of benzimidazole-peptide conjugates, expecting these new compounds to express
novel biological properties [2].
The peptide-heterocycle conjugates are obtained by the on-resin reaction between aldehydes and peptides
containing a specially designed β-(3, 4-diaminophenyl)alanine residue [3]. The stoichiometric amount of
aldehyde leads to 2’-substituted 3-(1H-benzimidazol-5-yl)alanine–containing peptides, whereas the increase in
aldehyde content results in 1’, 2’-disubstituted derivatives. The reaction with dialdehydes produces novel amino
acid residues containing tricyclic systems, in the case of o-phthalic aldehyde - the pyrido[1, 2-a]benzimidazole.
The compatibility of our method with the Fmoc solid-phase peptide synthesis protocols was further proven by
the synthesis of analogues of immunosuppressory fragments of ubiquitin and HLA-DQ [4, 5].
NH
O
N
N
H
1. 2 M SnCl 2 * 2H 2 O
2. 1.2 eq aldehyde, DMF
3. piperidine
4. TFA
1. 2 M SnCl 2 * 2H 2 O
2. 2 eq dialdehyde, DMF
3. piperidine
4. TFA
Fig. 1. On-resin synthesis of substituted 3-(benzimidazol-5-yl)alanines.
R
NH
NH
O
O
NH 2
NO 2
NH
1. 2 M SnCl 2 * 2H 2 O
2. 2.1 eq aldehyde, DMF
3. piperidine
4. TFA
Taking into account the known affinity of benzimidazoles to metal ions [6] we investigated the complexing
abilities of peptides containing substituted 3-(benzimidazol-5-yl)alanines using high resolution mass
spectrometry. We observed the formation of the complex of HLA-DQ fragment containing (2-(pyridin-2yl)benzimidazol-5-yl)alanine
with copper ion. The collision-induced dissociation of the investigated complex
indicates the part of the peptide-heterocycle conjugate that is involved in binding of the metal ion.
Our results demonstrate that the high resolution electrospray mass spectrometry is an ideal tool for studying
interactions of peptides with metal ions. The sub-femtomolar amount of sample required for measurement and
the possibility of analyzing mixtures, as well as the richness of information brought by the analysis of isotopic
patterns and the fragmentation pathways, make mass spectrometry an interesting alternative for investigating
bioinorganic compounds.
Acknowledgements: Supported by Grant No. N N 204 249934 from the MSHE (Poland).
References:
[1] A. Kluczyk, A. Staszewska, P. Stefanowicz et al., J. Peptide Sci., 12, 111 (2006).
[2] M. Koprowska-Ratajska, A. Kluczyk, P. Stefanowicz et al., Amino Acids, in press.
[3] A. Staszewska, P. Stefanowicz, Z. Szewczuk, Tetrahedron Lett., 46, 5525 (2005).
[4] Z. Szewczuk, P. Stefanowicz, A. Wilczynski et al., Biopolymers, 40, 571 (1996).
[5] Z. Szewczuk, P. Stefanowicz, A. Wilczynski et al., Biopolymers, 74, 352 (2004).
[6] M. Devereux, D. O’Shea, A. Kellett, J. Inorg. Biochem., 101, 881 (2007).
N
N
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279
O
N
N
R
R