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the scaffold, sequentially modified by 4-pentynoic acid using CuI and ascorbic acid [3].Synthesis of azido peptides was later improved by the solid phase diazotransfer reactionusing the reagent developed by Goddard-Borger and Stick [4].Subsequently, a second N 3 CH 2 COLeuPhe-OH moiety was introduced after Fmocremoval and 4-pentynoic acid coupling. The product was cleaved and the crude materialwas purified using reversed phase HPLC, yielding the dipodal peptide, 2, in 82% purity andan overall yield of 27%. This methodology demonstrates to us that it is possible tointroduce two different peptide chains in the future. Doing so, a library of potentialestrogen receptor mimics can be created.OOHHNNHOONN NNN NHNO ONHONHHNOHOO2OOHPeptide mimic 2 is completely symmetric, and thus an identical set of signals are found forthe leucine and for the phenylalanine residues from each of the two strands by NMR.Identification of each proton signal was not difficult due to the high purity of thecompound. Different chemical shifts for the δ protons from leucine can be explained, as thedelta protons from each methyl group are inequivalent. From the NOE contact between anamide proton from leucine and the aromatic protons from the phenylalanine side chain, itcould be proposed that these protons are involved in H bondings between chains due to thesterical hindrance between protons from the same chain. The hydrophobic cavity of 2 isprobably narrower than the cavity formed in 1.AcknowledgmentsThis research project is supported by a Marie Curie Early Stage training Fellowship of the EuropeanCommunity´s Sixth Framework Programme under contract number MEST-CT-2005-020643 and byGhent University. Katelijne Gheysen and prof. J. Martins from the NMR and Structural AnalysisGroup (UGent) are gratefully acknowledged for their scientific support.References1. a) Brzozowski, A.M., Pike, A.C.W, Dauter, Z., Hubbard, R.E., Bonn, T., Engström, O., Lars, O.,Greene, G.L. Nature 389, 753-758 (1997); b) Tannenbaum, D.M., Wang, Y., Shawn, P.W., Sigler,P.B. Proc. Natl. Acad. Sci. 95, 5998-6003 (1998).2. a) Rostovtsev, V.V., Green, L.G., Fokin, V.V., Sharpless, K.B. Angew Chem. Int. Ed. 41 2596-2599(2002); b) Tornoe, C.W., Christensen, C., Meldal, M. J. Org. Chem. 67, 3057-3064 (2002).3. Zhang, Z.S., Fan, E. Tetrahedron Letters 47, 665-669 (2006).4. Goddard-Borger, E.D., Stick, R.V. Org. Lett. 9, 3793-3800 (2007).267