Synthesis of tricyclic N,O-acetals from α-functionalized rubanone. A masked 1,2,3-tricarbonyl system from quinidine

Abstract

A series of protected 2-bromorubanones derived from quinidine has been prepared diastereoselectively and converted into tricyclic N,O-acetals containing a masked 1,2,3-tricarbonyl functionality. Good yields have been achieved using formyl-, acetyl- and propionyl-protecting groups. The novel one-pot conversion of protected 2-bromorubanones into tricyclic Cinchona cage compounds is suggested to include a reduction–oxidation sequence and an intramolecular acyl transfer.