parasitically on the black locust tree, Robinia pseudoacacia, by virtue of a reverse-
immunoaffinity system. Using an LC/MS procedure, milligram quantities of (±)-laetirobin (1)
were obtained, and the structure of 1 was elucidated by X-ray crystallography and confirmed
by NMR spectroscopy. Preliminary cellular studies indicated that (±)-laetirobin (1) rapidly
enters in tumor cells, blocks cell division at a late stage of mitosis, and invokes apoptosis.