Synthesis of the Cyclic Hexapeptide Echinocandin D. New Approaches to the Asymmetric Synthesis of ,&Hydroxy a-Amino Acids


Derivatives of the two unusual 8-hydroxy amino acids in echinocandin D (1) have been synthesized by employing asymmetric glycine enolate aldol methodology. The N-Boc,O-benzyl derivative of (2S,3R)-3-hydroxyhomotyrosine (Hht) (2) and the methyl ester of (2.9,3S,4.9)-3-hydroxy-4-methylproline (Hmp) (3) have been synthesized in four steps each from… (More)