Isolation and structure determination of malevamide E, a dolastatin 14 analogue, from the marine cyanobacterium Symploca laete-viridis.

A new depsipeptide, malevamide E (1), was isolated from field-collected colonies of the filamentous cyanobacterium Symploca laete-viridis. The gross structure of 1 was determined by spectroscopic analyses, including one- and two-dimensional NMR and accurately measured MS/MS. Chiral HPLC analyses of an acid hydrolysate of 1 allowed the stereochemical assignments of its amino acid residues, which include N-methyl-L-alanine, alpha-N,gamma-N-dimethyl-L-asparagine, N-methyl-L-phenylalanine, L-proline, D-valine, and N-methyl-L-valine.

Malevamide D: isolation and structure determination of an isodolastatin H analogue from the marine cyanobacterium Symploca hydnoides.

Malevamide D (1), a highly cytotoxic peptide ester, and the known compound curacin D (5) were isolated from a Hawaiian sample of Symploca hydnoides. The structure of 1 was elucidated by spectroscopic analysis including NMR and high-resolution MS/MS. Partial stereochemical assignments of 1 were made by chiral HPLC analysis of acid and base hydrolysates.