The isolation and structure elucidation of three new secondary metabolites, chaetoglobosin-510 (1), -540 (2), and -542 (3), are described. These compounds were produced by cultures of the marine-derived fungus Phomopsis asparagi, challenged with the known F-actin inhibitor jasplakinolide. Chaetoglobosin-542 (3) displayed antimicrofilament activity and was cytotoxic toward murine colon and leukemia cancer cell lines.