Synthesis of the chlorofusin cyclic peptide: Assignment of the asparagine stereochemistry

[GRAPHICS] An efficient synthesis of two diastereomers of the chlorofusin cyclic peptide bearing either the L-Asn3/D-Asn4 or D-Asn3/L-Asn4 stereochemistry is detailed. Four key subunits were prepared, sequentially coupled, and cyclized to provide the two diastereomeric macrocycles. The absolute stereochemistry at the asparagine residues 3 and 4 was assigned as L and D, respectively, by correlating the NMR data of the two diastereomers with that reported for the natural product.