| Abstract: | In order to explore the route for the preparation of cyclodepsipeptide by cyclization through an ester bond formation, two analogs of AM-toxin II, cyclotetradepsipeptide, were synthesized. As a preliminary experiment, synthesis of [L-Phe3, L-Ser(Bzl)4]-AM-toxin II, containing L-Phe and L-Ser(Bzl) in place of L-App (2-amino-5-phenyl-pentanoic acid) and ΔAla (α,β-dehydroalanine), respectively, was attempted. Cyclization of H-L-Hmb-L-Phe-L-Ser(Bzl)-L-Ala-OH in CH2CI2 at 10mM concentration using water-soluble carbodiimide (EDC) and 4-dimethylaminopyridine (DMAP) successfully gave a cyclic monomer in 16% yield. Cyclization of H-L-Hmb-L-App-L-Ser(Bzl)-L-Ala-OH under the same conditions also afforded a cyclic monomer, [L-Ser(Bzl)4]AM-toxin II, in 19% yield. Analytical parameters of these cyclic monomers obtained were identical to those of the authentic samples obtained by cyclization through a peptide bond formation. |
