IB-01212, a new cytotoxic cyclodepsipeptide isolated from the marine fungus Clonostachys sp. ESNA-A009

IB-01212, a new cytotoxic cyclodepsipeptide featuring C2 symmetry, was isolated from the mycelium extract of Clonostachys sp. ESNA-A009. The amino acid sequence of the compound was determined by spectroscopy techniques. The absolute configuration of the amino acids was determined by a combination of the Marfey and menthol methods. The structure, which was confirmed by comparison of the analytical data for the natural product with a sample obtained by solid-phase peptide synthesis, was revealed to be a cyclic dimer formed by two chains of L-N,N-Me2Leu-L-Ser-L-N-MeLeu-L-N-MePhe bound by the two esters formed between the carboxylic acid of the L-N-MePhe and the hydroxyl function of the L-Ser. IB-01212 is highly cytotoxic to different tumor cell lines.