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Proceedings of the 31 st European Peptide SymposiumMichal Lebl, Morten Meldal, Knud J. Jensen, Thomas Hoeg-Jensen (Editors)European Peptide Society, 2010Synthesis and Biological Evaluation of New Linear and CyclicAnalogues of NeurotensinRevekka Exarchakou 1 , Vassiliki Magafa 1 , Evy Manessi-Zoupa 2 ,Nikos L. Assimomytis 3 , Maria Georgiadou 4 , Maria Venihaki 5 ,George Varvounis 6 , George Liapakis 4 , and Paul Cordopatis 11 Department of Pharmacy, University of Patras, GR-26500, Patras, Greece; 2 Departmentof Chemistry, University of Patras, GR-26500, Patras, Greece; 3 Department of MechanicalEngineering, TEI of Patras, 1 M. Alexandrou str, Koukouli, GR-26334, Patras, Greece;4 Department of Pharmacology, 5 Department of Clinical Chemistry, Faculty of Medicine,University of Crete, GR-71003, Heraklion, Crete, Greece; 6 Department of Chemistry,University of Ioannina, GR-45110, Ioannina, GreeceIntroductionNeurotensin [(pGlu-Leu-Tyr-Glu-Asn-Lys-Pro-Arg-Arg-Pro-Tyr-Ile-Leu), NT] is atridecapeptide originally isolated from bovine hypothalamus and later from intestines. NTdisplays a wide spectrum of biological actions both in the central and peripheral nervoussystems of different mammalian species [1]. The physiological and biochemical actions ofNT are mediated through binding to NT receptors (NTS1, NTS2 & NTS3) [2]. All threereceptors recognize the same C-terminal hexapeptide fragment of NT [NT(8-13)]. AlthoughNT(8-13) possesses high receptor binding affinity, it is rapidly degraded by peptidaseaction. Therefore, it is important to synthesize analogues with stabilized bonds againstmetabolic deactivation which do not lose binding affinity. Based on these findings, weherein report the synthesis of new linear and cyclic analogues of NT(8-13) withmodifications in the basic structure needed for high affinity binding in order to improve themetabolic stability. The analogues contain D-Tyrosine(Ethyl) [D-Tyr(Et)] in position 11,D-Arginine in position 8 or 9, L-Lysine in position 8 or 9 and 1-[2-(aminophenyl)-2-oxoethyl]-1H-pyrrole-2-carboxylic acid (AOPC) in position 8 or 7. AOPC is an unnaturalamino acid with promise in applications as a building block for the synthesis ofpeptidomimetic compounds.Results and DiscussionAll analogues shown in Table 1 were synthesized by the Fmoc/Bu t solid phasemethodology [3] utilizing 2-chlorotrityl chloride resin [4]. Stepwise synthesis of a peptideanalogue was achieved with diisopropylcarbodiimide/1-hydroxybenzotriazole (DIC/HOBt)as coupling agents in dimethylformamide (DMF) [5,6] in 2.0 (Fmoc-amino acid), 2.2 (DIC)and 3.0 (HOBt) molar excess for 2 h at room temperature. AOPC was synthesized in foursteps from 1-(2-nitrophenyl)ethanone (Scheme 1). The coupling of the carboxylic acidC-terminus of AOPC with the N-terminus of the peptides took place with 2-(1Hbenzotriazole1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate (TBTU), 1-hydroxybenzotriazole (HOBt) and diisopropyl ethylamine (DIEA) in DMF [7] without protection ofthe AOPC amino group. The overall yield of the syntheses of the NT analogues was in theiNO 2iiNH 2NO 2MeOOBrOBrabciii MeO 2CNHdNH 2CO 2HNO1ivNH 2CO 2MeNOeScheme 1. Synthesis of 1-[2-(aminophenyl)-2-oxoethyl]-1H-pyrrole-2-carboxylic acid(AOPC). Reagents and conditions: (i) Br 2 , chloroform, 83%, (ii) Cu, H 2 SO 4 , 57%, (iii)K 2 CO 3 , DMF, 66%, (iv) (a) ΝaOH, H 2 O, MeOH, 60 o C, (b) 2 N HCl, 87%.446