2014•South African Journal of ChemistryOpen access
Conformational Comparison of Cyclic α 3 β Tetrapeptide vs. α 3 β Pentapeptide
SA Pawara, AM Jabgunde, Gem Maguire, DD Dhavale, HG Kruger, Fernando Alberício
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Abstract
The γ-turn inducing sugar β-amino acid plays an important role in the formation of well-defined secondary structures of cyclic tetra- and pentapeptide. Two tetra- and one novel pentapeptide were synthesized from a sugar β-amino acid and the conformations of the compounds were established by NMR spectroscopy (EASY-ROESY) and compared with CD spectroscopic data. Although the a-turn conformation was dominant for both tetra- and pentapeptide according to NMR spectroscopic analysis in DMSO, the pentapeptide exhibited the presence of a second conformation.CDspectroscopic results in methanol showed that the tetrapeptides have a γ-turn conformation, while the pentapeptide has a random structure. KEYWORDS : Cyclic peptide, tetrapeptide, pentapeptide, conformational analysis, NMR spectroscopy, CD spectroscopy.