A Practical Asymmetric Synthesis of Enantiopure Spiro[4,4]nonane‐1,6‐dione

AbstractA practical asymmetric synthesis of enantiopure spiro[4,4]nonane‐1,6‐dione, a valuable precursor for chiral ligand development, is reported. This synthetic strategy includes a kinetic resolution of the readily synthesized ketone precursor with a chiral quaternary carbon center by bioreduction with baker’s yeast as the key step, followed by a hydroformylation, oxidation, esterification and Dieckmann cyclization reaction sequence to generate the spiro five‐membered ring. It was found that the masking of the β‐ketone carbonyl group of enantiopure ethyl 1‐allyl‐2‐oxocyclopentanecarboxylate via formation of a ketal with 1,3‐diol derivative is necessary during the process of Dieckmann condensation in order to prevent its racemization under basic conditions. This method allows the gram‐scale preparation of both enantiomers of spiro[4,4]nonane‐1,6‐dione (1) with excellent enantiopurities (up to >99% ee) in the overall yields of 54% [(R)‐1] and 42% [(S)‐1], respectively. The practicality of the present synthetic procedure has provided a fundamental platform for the development of spiro[4,4]nonane‐1,6‐dione‐based chiral chemistry.