The Asymmetric Chelate-Claisen Rearrangement as a Key Step in the Syntheses of Non-Proteinogenic Amino Acids

Allylic esters of TFA-protected amino acids undergo asymmetric Claisen rearrangements in the presence of cinchona alkaloids, giving rise to γ,δ-unsaturated amino acids in a highly stereoselective fashion. The products are useful precursors for the short and efficient synthesis of more complex compounds such as substituted 4-hydroxyornithines and iminosugars. Starting from the unsaturated amino acids, iodolactonization, bicylization and opening of the lactone ring with nucleophiles such as amino acids or peptides provide hydroxyproline derivatives directly incorporated into peptides.

asymmetric Claisen rearrangements - iminosugars - iodolactonization - peptides - prolines