Application of carbodiimide mediated Lossen rearrangement for the synthesis of α-ureidopeptides and peptidyl ureas employing N-urethane α-amino/peptidyl hydroxamic acids

Application of the Lossen rearrangement to the synthesis of N-urethane protected α-peptidyl ureas and ureidopeptides is reported. The carbodiimide mediated rearrangement of N-Boc/Z/Fmoc protected α-amino/peptide hydroxamic acids into isocyanates and coupling of the latter with the amino acid esters/peptide esters have been accomplished in a single-pot to obtain good yields of urea products. Synthesis of the ureidoalanine derivatives via the hydroxamate derivatives of N-protected aspartic acid has also been carried out using the same procedure.