Discovery of novel ansamycins possessing potent inhibitory activity in a cell-based oncostatin M signalling assay.

We describe the isolation and characterisation of novel non-benzoquinone ansamycin metabolites related to geldanamycin from a culture of Streptomyces sp. S6699. The compounds possess potent inhibitory activity in a cell-based assay measuring inhibition of oncostatin M signalling in a reporter cell line utilising a secreted placental alkaline phosphatase (sPAP) readout. In this paper we report the isolation and structure elucidation of the compounds and describe some of their biological properties.