SYNTHESIS OF TRICYCLIC N,O-ACETALS FROM ALPHA-FUNCTIONALIZED RUBANONE- A MASKED 1,2,3-TRICARBONYL SYSTEM FROM QUINIDINE

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