Fischer Reaction in the Synthesis of New Triterpene Indoles of the Fusidane Series

The Fischer reaction of 3,11-dioxo derivatives of fusidic acid and its esters with phenylhydrazine chemoselectively occurred at the 3-position with the formation of indole-fused fusidane triterpenoids. The reaction with 3-chlorophenylhydrazine under similar conditions afforded mixtures of isomeric 6- and 4-chloro derivatives at a ratio of 3:2. 2,4-Dinitrophenylhydrazine reacted with the same fusidane diketones to give the corresponding hydrazones at the 3-oxo group. Biological screening of the synthesized compounds revealed derivatives exhibiting a high antibacterial activity against methicillin-resistant Staphylococcus aureus with a minimum inhibitory concentration of ≤0.25 μg/mL.