Selective cytotoxicity and stereochemistry of aspochalasin D.

The oncogenic ras functions as an apoptosis suppressor as well as a cell-growth stimulator1^ Thus, selective apoptosis inducers in ras-dependent cells are expected to be new anticancer agents against cells expressing constitutively active mutant ras. In the course of our screening2^ for microbial products with selective cytotoxicity against /m-dependent Ba/F3 cells, Aspergillus sp. AJ1 17509 was found to produce an active substance (1). The producing organism was cultivated in 500-ml Erlenmeyer flasks containing 100ml of a medium consisting of soluble starch 3.0%, sucrose 1.0%, Pharmamedia 1.0%, Polypepton 0.5% Distiller's soluble 0.5%, MgSO4 0.05%, CaCO3 0.3% and NaCl 0.1% (pH pp.379 381