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Small Cyclic Disulfide Peptides: Synthesis in Preparative Amounts and Characterization by Means of NMR and FT‐IR Spectroscopy
Author(s) -
Kolano Christoph,
Gomann Klaus,
Sander Wolfram
Publication year - 2004
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200400174
Subject(s) - chemistry , cyclic peptide , nuclear magnetic resonance spectroscopy , yield (engineering) , intramolecular force , thiol , proton nmr , amide , spectroscopy , disulfide bond , peptide , organic chemistry , biochemistry , materials science , physics , quantum mechanics , metallurgy
Abstract Two cyclic disulfide‐bridged tetrapeptides [cyclo(Boc−Cys−Pro−Aib−Cys−OMe) and cyclo(Boc−Cys−Pro−Phe−Cys−OMe)] were prepared in high yield and purity. The use of double‐walled reaction flasks, which were attached to an external cryostat, gave perfect temperature control of the reaction. The acetamidomethyl and trityl group were used for the protection of the thiol groups of Cys. Disulfide bond formation was obtained by cleavage of the protection groups and subsequent oxidation of the free thiols with iodine under high dilution conditions in one step. The obtained cyclic peptides were checked for purity by analytical HPLC, and identified by NMR spectroscopy and a variety of standard analytical methods (IR, m. p., FAB‐MS, ELA, TLC). Conformational properties of the peptides were derived from one‐ and two‐dimensional NMR experiments. Temperature‐dependent NMR and FT‐IR experiments allowed for the determination of the degree of inter‐ and intramolecular hydrogen bonding of the cyclic tetrapeptides. The results from the temperature‐dependent NMR experiments are in good agreement with the observed dynamics of the peptides in the amide I and II region, which were determined by means of temperature‐dependent FT‐IR spectroscopy using the ATR technique. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)