Synthesis 2011(4): 653-661  
DOI: 10.1055/s-0030-1258396
PAPER
© Georg Thieme Verlag Stuttgart ˙ New York

A Practical Large-Scale Synthesis of Cyclic RGD Pentapeptides Suitable for Further Functionalization through ‘Click’ Chemistry

Jiří Paleček, Gerald Dräger, Andreas Kirschning*
Institut für Organische Chemie and Biomolekulares Wirkstoffzentrum (BMWZ), Leibniz Universität Hannover, Schneiderberg 1b, 30167 Hannover, Germany
e-Mail: andreas.kirschning@oci.uni-hannover.de;
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Publikationsverlauf

Received 18 November 2010
Publikationsdatum:
11. Januar 2011 (online)

Abstract

A multigram batch of the cyclo[Arg-Gly-Asp-d-Phe-Lys] and its N-ε-azido derivative was accomplished via solution-phase synthesis using an epimerization-free fragment condensation. The C-terminus of d-Phe was protected as its tert-butyl ester. Fmoc (Arg, Gly, Asp, d-Phe) and Boc (Lys) groups were used to protect all N-α-termini. The Ts and NO2 groups, respectively were chosen to protect the guanidine group. The macrocyclization step (between d-Phe and l-Lys) was carried out under TBTU/HOBt or DPPA condensation conditions. Finally, the ε-amino group of the lysine residue was selectively converted into the azido group by a diazo-transfer reaction.