spiro-Oxanthromicin was first isolated from a soil-derived Streptomyces sp. by Capon and co-workers in 2014. spiro-Oxanthromicin inhibits mislocalisation of the oncogenic mutant K-Ras from the plasma membrane of intact Madin-Darby canine kidney (MDCK) cells (IC50 27 µM) and is highly synergistic with its co-metabolites including (±)-oxanthromicin in this assay. spiro-Oxanthromicin inhibits Bacillus cereus (MIC 12.5 µg/mL) but was inactive against HSV-1, Mycobacterium tuberculosis H37Ra and phytopathogenic fungi. spiro-Oxanthromicin shows minimal cytotoxicity.