title: Studies on the synthesis of peptides containing dehydrovaline and dehydroisoleucine based on copper-mediated enamide formation.
abstract: The preparation of peptide fragments containing dehydrovaline and dehydroisoleucine moieties present in the antibiotic myxovalargin is reported. Peptide formation is based on a copper-mediated C-N cross-coupling protocol between an acyl amide and a peptidic vinyl iodide. The presence of a neighboring arginine in the vinyl iodide posed a challenge with respect to the choice of the protecting group and the reaction conditions. It was found that ornithine - a suitable precursor - is better suited than arginine for achieving good yields for the C-N cross-coupling reaction. The optimized conditions were utilized for the synthesis of peptides 32, 33, 39 and 40 containing a neighboring ornithine as well as for the tripeptide 44 containing dehydroisoleucine with the correct stereochemistry.
authors.affiliation: Institute of Organic Chemistry and Center of Biomolecular Drug Research (BMWZ), Leibniz University Hannover, Schneiderberg 1b, 30167 Hannover, Germany.
authors.forename: Franziska
authors.initials: F
authors.lastname: Gille
authors.affiliation: Institute of Organic Chemistry and Center of Biomolecular Drug Research (BMWZ), Leibniz University Hannover, Schneiderberg 1b, 30167 Hannover, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Kirschning
keywords: Hartwig–Buchwald reaction; catalysis; dehydroamino acids; myxovalargin; peptides