Pemuchiamides A and B, Proline-Rich Linear Lipopeptides, Isolated from a Marine <i>Hormoscilla</i> sp. Cyanobacterium

Pemuchiamides A and B (<b>1</b> and <b>2</b>) were isolated from a marine <i>Hormoscilla</i> sp. cyanobacterium collected from Pemuchi Beach on Hateruma Island, Japan. Although <b>1</b> and <b>2</b> existed as a complex mixture of rotamers in chloroform-<i>d</i>, detailed analyses of their 2D NMR and tandem mass spectra revealed their planar structures, respectively. The absolute configurations of <b>1</b> and <b>2</b> were established via the degradation and derivatization reactions. Pemuchiamide A (<b>1</b>) exhibited potent growth-inhibitory activity against <i>Trypanosoma brucei rhodesiense</i>, the causative organism of African sleeping sickness, while <b>2</b> showed 10-fold weaker activity than <b>1</b>. This result indicates that the presence of a hydroxy group at the C-3 position of the 4-aminobutanoic acid moiety negatively affects antitrypanosomal activity.