Syntheses of four unusual amino acids, constituents of cyclomarin A

Abstract The stereoselective syntheses of four unusual amino acids, constituents of cyclomarin A, are described. The protected N -methylhydroxyleucine 2 was synthesized using Evans’ asymmetric azide-transfer reaction. The unusual amino acid 3 was prepared via diastereoselective methylation of the l -aspartic acid derived lactone 13 . The stereoselective formation of threo-β-methoxyphenylalanine 4 was performed via aldol reaction using Schollkopf's chiral glycine enolate. The synthesis of N -reverse prenylated tryptophane 5 was achieved by the AQN ligand-promoted Sharpless regioreversed asymmetric aminohydroxylation protocol.

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