Proceedings book download - 5Z.com

Proceedings of the 31 st European Peptide SymposiumMichal Lebl, Morten Meldal, Knud J. Jensen, Thomas Hoeg-Jensen (Editors)European Peptide Society, 2010Solvent-Free Synthesis of Peptides in a Ball-MillValérie Declerck, Pierrick Nun, Jean Martinez, and Frédéric LamatyInstitut des Biomolécules Max Mousseron (IBMM), UMR 5247 CNRS-UM1-UM2,Université Montpellier II, Place Eugène Bataillon, 34095, Montpellier Cedex 5, FranceIntroductionThe market for therapeutic bulk peptides is expected to rapidly grow in the next few years[1]. In spite of the well established procedures of peptide synthesis by chemical ways, i.e.stepwise synthesis in solution, solid phase peptide synthesis, one of the major problemsrelated to peptide synthesis concerns the huge amount of solvent needed for theirpreparation, particularly on solid supports (2000 to 5000 kg for a large peptide). There isstill a need for exploring efficient, convenient, and environmentally friendly methods forpeptide synthesis, particularly when the time for scale-up of peptide production comes. Apossible approach to solve this problem would be to carry out chemical reactions in theabsence of solvent [2]. Techniques such as mixing, grinding or ball-milling have provedtheir efficiency in the field of organic chemistry in the solid state. We report herein a newstrategy for the preparation of peptides in solvent-free conditions, using ball-millingtechnology [3].Results and DiscussionThe coupling of urethane-protected N-carboxyanhydride of aminoacids (UNCA’s) 1 withaminoacids or aminoesters was studied, keeping in mind that all these compounds have toremain in their solid state under the ball-milling conditions (Scheme 1). UNCA’s areactivated forms of aminoacids which have proven to be useful in peptide and organicsynthesis.The various UNCA derivatives do not present the same reactivity profile. Boc-Val-NCA was quantitatively converted to the dipeptide while Fmoc-Val-NCA gave lowerconversions. Very good yields were achieved with Boc-Phe-NCA except for the reaction ofHCl·H-Phe-OMe. It is worth noting that better results were obtained with freshly preparedstarting material, otherwise, the reaction was incomplete and hydrolysis of the UNCAoccurred.Scheme 1.PGPG = Boc, Fmoc1We also explored the possibility of preparing a tripeptide, from a dipeptide. Starting fromHCl.Ala-Gly-OMe, it was possible to prepare the corresponding tripeptide after reactionwith Boc-Val-NCA (Scheme 2). This is the first step towards the development of aniterative process to synthesize longer peptides, by successive reaction with urethaneprotectedN-carboxyanhydride of aminoacids. We also experimentally checked that thismethod does not lead to any epimerization of the peptide during its synthesis.Scheme 2.ONR 1OO+HCl·H 2 NOR 2 OR 3NaHCO 3ball-milling1h, 30HzPGNHR 1HNOO R 2 OR 3BocONOOO+ HCl·H 2 NOMeNHCH 3 ONaHCO 3ball-milling1h, 30HzBocNHOHNOCH 3NHOOMe164