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Total Synthesis of Cyclotheonamide C by Use of an α-Keto Cyanophosphorane Methodology for Peptide Assembly†
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Respectfully dedicated to Professor Jean-Claude Gramain
Abstract
The total synthesis of cyclotheonamide C (3), a macrocyclic pentapeptide incorporating an α-keto homoarginine (k-Arg) and a vinylogous dehydrotyrosine (V-ΔTyr) unit, has been achieved. For comparison of macrocyclisation feasibility, two linear pentapeptides bearing free ketone functions at the k-Arg units were prepared, by use of tandem oxidation/coupling reactions on α-keto cyanophosphorane precursors as the key processes for pentapeptide elaboration. Successful activation and coupling at the pentapeptide V-ΔTyr C terminus led to the target molecule core, and thus provided a short total synthesis of the target compound.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)