Cytochalasin W, a new 24-oxa[14]cytochalasan from Phoma exigua var. heteromorpha.

A further cytochalasin was isolated from liquid culture filtrates of Phoma exigua var. heteromorpha together with cytochalasins U and V and other well-known cytochalasins. The metabolite, named cytochalasin W, was characterized by spectroscopic and chemical methods as a new 24-oxa[14]cytochalasan, bearing a formyl group on the macrocyclic ring. Cytochalasin W showed toxic activity in the brine shrimp assay.