Aspertides A-E: Antimicrobial Pentadepsipeptides with a Unique -Methoxycinnamoyl Amide Group from the Marine Isolates MA-21 and SD-512.

Marine fungus-derived natural products are an important source of antimicrobial compounds against marine aquatic pathogens. Here, we describe the isolation and characterization of five new pentadepsipeptides, aspertides A-E (-), containing a unique -methoxycinnamoyl amide group, from the marine fungi MA-21 and SD-512. Among them, aspertides B-E (-) also possessed uncommon amino acid residues, such as 3-hydroxyproline, 2,3-dihydroxyproline, or pipecolinic acid. The structures of these compounds were elucidated on the basis of NMR and mass spectroscopic analyses. The absolute configurations of them were established by chiral HPLC analyses of the acidic hydrolysates and NMR calculations with DP4+ probability analysis. In bio-activity assays, compounds and exhibited antibacterial activities against aquatic-pathogenic bacteria, including , , , and with MIC values of 8-32 μg/mL.