A straightforward method for the synthesis of polyhydroxylated alpha-amino acid N-carboxy anhydrides (NCAs) is described as the means by which short peptide segments comprised of a polyhydroxylated chain are easily affordable. The entire sequence lies in the preparation of nonracemic 3-hydroxy beta-lactams through the highly diastereoselective Staudinger reaction of hydroxyketene equivalents with chiral alpha-oxyaldehyde-derived imines, followed by TEMPO radical assisted cycloexpansion to the corresponding NCA and subsequent peptide coupling with alpha-amino acid esters. The method has been applied to the synthesis of short peptide segments derived from carbamoylpolyoxamic acid, some glycoglycines, as well as C(2) symmetric hydroxy amino acids.
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