Cylic peptides. I. Synthesis of AM-toxin analog containing O-methyl-l-tyrosine.

An AM-toxin analog, cyclotetradepsipeptide, containing an O-methyl-L-tyrosine residue in place of an L-2-amino-5-arylpentanoic acid residue in AM-toxins has been prepared by a conventional method. The synthesis was attempted through six different routes and the desired analog was obtained by one such procedure. This compound showed extremely weak activity in causing necrosis on apple leaves.