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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 of Peptidomimetics Mimicking the Hormone BindingDomain of the Estrogen ReceptorRosa Romeralo Tapia, Fréderique Backaert, Jan Goeman, andJohan Van der EyckenLaboratory for Organic and Bioorganic Synthesis, Department of Organic Chemistry,Ghent University, Krijgslaan 281 (S4), B-9000, Ghent, BelgiumIntroductionEndocrine disrupting chemicals (EDC’s) are an important class of pollutants, which have incommon that they show affinity for the hormone-binding domain of the estrogen receptor(HBD-ER), thus disturbing the endocrinal system. Detection in wastewater has not beensuccessful due to their low concentration. Therefore, new sensitive screening methods arehighly demanded. A possible solution is to preconcentrate them using estrogen receptormimics for solid phase extraction. To this end, a dipodal peptidomimetic of the HBD-ERwill be attached on a solid support. Amino acids known to be important for the estrogenreceptorinteraction will be preferably incorporated [1] onto the aromatic scaffold: 3,5-diamino benzoic acid.Results and DiscussionThe first peptide mimic was built using standard solid phase Fmoc-linear peptidechemistry. Fmoc-Gly-OH was introduced as the first residue. Coupling of non-polar aminoacids (Ala, Leu and Phe) and Glu via amide bond formation was optimized. Finally, thepeptidomimic, 1 was purified by RP-HPLC.OOHHNNHONHOOHNOHNHOOCNHONHOOHNOHNO1ONHNMR characterization was performed in order to confirm the amino acid sequence and toget information about the three dimensional arrangement, like possible chain interactionsand H bonding. Chemical shifts of every residue were assigned in 2D TOCSY and thesequence was confirmed by NOE contacts between adjacent amino acids leading to theverification of the two peptidic arms in N to C direction: Ala-Ala-Glu-Gly and Phe-Leu-Ala-Gly. To analyze the possible H bonding between chains or nonadjacent residues, thedecay of amide proton signal intensities due to hydrogen exchange spectra was analyzed.The most evident result is found in the amide proton from the phenylalanine residue wherethe signal disappears when the solvent was changed from H 2 O to deuterated water. Fromthis experiment we can conclude that these protons are not involved in H bondings, makingthe H easily accessible for the exchange with the solvent. The less intense decay isobserved for the amide protons of the leucine and the alanine. On the other hand, all amideprotons from the second synthesized strand, Gly-Glu-Ala-Ala, showed decay after solventwas changed to D 2 O.Secondly, a convergent route based on click chemistry [2] was explored for an easiercoupling of the amino acid on the electron-poor amine of this scaffold. First, the synthesisof azido peptides was performed using 2-chlorotrityl chloride resin as solid support. Afterthe synthesis of the peptides, azidoacetic acid was coupled in the last amino position.Coupling yields were followed by measurements of UV absorption of the dibenzofulveneadduct of aliquots taken from the resin. The crude cleaved azido peptides were clicked onto266