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The final deprotection of the protected peptides was performed by reacting withreagent K (20ml/g peptide) for 2 h at room temperature. The crude product was in generalof good purity as shown by analytical HPLC analysis.Synthesis was carried out using 2-chlorotrityl chloride resin (1.0 mmol/g) followingstandard Fmoc strategy. Fmoc-Pro-OH (3.54 g, 10 mmol) was attached to the 2-CTC resin(5.0 g) with DIPEA (6.85 ml, 40 mmol) in anhydrous DCM:DMF (50 ml, 1:1) at roomtemperature for 2 h. After filtration, the remaining trityl chloride groups were capped by asolution of DCM:MeOH:DIPEA (17:2:1, 120 ml) for 30 min. The resin was filtered andwashed thoroughly with DCM (1×20 ml), DMF (4×20 ml) and MeOH (5×20 ml). Theloading capacity was determined by weight after drying the resin under vacuum and was1.0. The resin-bound Fmoc-amino acid was washed with DMF (3×20 ml) and treated with25% piperidine in DMF (65 ml) for 30 min. and the resin was washed with DMF (3× 20ml). Then a solution of Fmoc-AA-OH (7.5 mmol), TBTU (2.40 g, 7.5 mmol), DIPEA (3.0ml, 17.5 mmol) in 30 ml DMF was added to the resin-bound free amine and shaken for 1 hat room temperature. After completion of coupling, resin was washed with DMF (4×20 ml)and DCM (1×20 ml). The coupling was repeated as the same methods for other amino acidsof their sequences. In all cases for the presence or absence of free primary amino groups,Kaiser Test was used. Fmoc determination was done using UV spectroscopy method.In conclusion, fertirelin acetate was synthesized using Fmoc strategy and novelamidation method using ethyl ammonium hydrochloride in solution phase, in good yield.AcknowledgmentsWe are grateful Kimia Exir Company for Chemicals donation. A part of this research work wassupported by research council of K.N. Toosi University of Technology which is gratefullyacknowledged. We also thank Tofigh Daru Research & Engineering Co. for kind cooperation.References1. Sasaki, K., et al. Nature 257, 751-757 (1975).2. Shinigawa, S., Fujino, M. Chem. Pharm. Bull. 23, 229-232 (1975).3. Yamada, K., Nakao, T., Nakada, K., Matsuda, G. Animal Reproduction Science 74, 27-34 (2002).4. Inaba, T., Tani, H., Gonda, M., Nakagawa, A., Tamada H., Sawada, T. Theriogenology 49, 975-982(1998).5. Rettmer, I., Stevenson, J.S., Corah, L.R. J. Anim. Sci. 70, 7-12(1992).6. a) Bui, C.T., Bray, A.M., Nguyen, T., Ercole, F., Maeji, N.J. J. Peptide Sci. 6, 243 (2000); b)Kappel, J.C., Barany, G. J. Peptide Sci. 11, 525 (2005); c) Stathopoulos, P., Papas, S., Tsikaris, V.J. Peptide Sci.12, 227 (2006); d) Maeda, D.Y., Ishmael, J.E., Murray, T.F., Aldrich, J.V. J. Med.Chem. 43, 3941 (2000); e) Deeks, T., Crooks, P.A., Waigh, R.D. J. Med. Chem. 26, 762 (1983).327