Polydiscamide A: a new bioactive depsipeptide from the marine sponge Discodermia sp

The Caribbean marine sponge Discodermia sp. yields polydiscamide A, a discodermin depsipeptide that inhibits the growth of the human lung cancer A549. Spectroscopic, chemical degradation and analogue studies reveal a structure composed of 13 amino acids, including a unique 3-methylisoleucine. The side-chain phenylalanine is replaced by p-bromophenylalanine. The lactone ring has five instead of six amino acids. Valine and proline replace the leucine, threonine and sarcosine in the ring. Except for asparagine, which exhibits a D configuration, the common amino acids show the same absolute configuration as in other discodermins.