3-O-Formyl-27-Hydroxyfusidic Acid: A New Metabolite of Fusidic Acid by Cunninghamella echinulata

Minor metabolites of fusidic acid (1) using the fungus Cunninghamella echinulata NRRL 1382 were investigated for discovering previously unstudied reactions. An unprecedented fusidic acid derivative, 3-O-formyl-27-hydroxyfusidic acid (2) was isolated, and its chemical structure was fully elucidated using various spectroscopic techniques including 1D, 2D NMR and HRESIMS. This is the first report for formylation reaction by C. echinulata.