Cytochalasins U and V, two new cytochalasans, from Phoma exigua var. heteromorpha

Two additional cytochalasins were isolated from liquid culture filtrates of Phoma exiqua var. heteromorpha together with some already known cytochalasins. The two new metabolites, named cytochalasin U and V, represent the first natural occurrence of a 25,26-dioxa[16] and 25-oxa[15]cytochalasan, respectively, both bearing a formyl group on the macrocyclic ring. Cytochalasins U and V showed respectively significant and weak activity in the brine shrimp assav. © 1992.