Laucysteinamide A (<b>4</b>) is a marine natural product isolated from the cyanobacterium <i>Caldora penicillata</i> and contains structural motifs found in promising cancer drug leads. The first total synthesis of <b>4</b> and its analogues was achieved, which also enabled a concise formal synthesis of somocystinamide A (<b>3</b>), a dimeric congener of <b>4</b> that previously showed extremely potent antiproliferative activities. This work provides further insights on structure-activity relationships in this class of natural products.