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.
Highlights
Dehydroamino acids [1] are rare amino acids that are constituents of many oligopeptides from microbial sources
As part of our study on the total synthesis of myxovalargin (1), a secondary metabolite from Myxococcus fulvus with antibacterial activity [14,15], we report on copper-mediated cross-coupling chemistry to create peptide fragments bearing dehydrovaline and dehydroisoleucine
We report on the synthesis of dehydrovaline and dehydroisoleucine-containing oligopeptides as found in the peptide antibiotic myxovalargin using a C–N cross-coupling approach
Summary
Dehydroamino acids [1] are rare amino acids that are constituents of many oligopeptides from microbial sources. Scheme 2: The Buchwald cross-coupling reaction in the preparation of peptides containing dehydroamino acids 4. As part of our study on the total synthesis of myxovalargin (1), a secondary metabolite from Myxococcus fulvus with antibacterial activity [14,15], we report on copper-mediated cross-coupling chemistry to create peptide fragments bearing dehydrovaline and dehydroisoleucine.
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