Characterization, Synthesis and Self‐Aggregation of (−)‐Alternarlactam: A New Fungal Cytotoxin with Cyclopentenone and Isoquinolinone Scaffolds

(-)-Alternarlactam [(-)-1], a new promising cytotoxin against two human cancer cell lines, was isolated from an endophyte culture and synthesized (along with (+)-1) from readily available starting materials. The absolute configuration, chirality-activity relevance and self-aggregation of (-)-1 were assigned by a combination of synthetic, spectroscopic and computational approaches. The full characterization of the new fungal cytotoxin may provide valuable information in the discovery of new antitumor agents.