Enantioselective synthesis of (+)-estrone exploiting a hydrogen bond-promoted Diels-Alder reaction.

Starting from Dane's diene and methylcyclopentenedione, (+)-estrone is synthesized along the Quinkert-Dane route in 24% total yield. The key step is an enantioselective Diels-Alder reaction promoted by an amidinium catalyst as efficiently as by a traditional Ti-TADDOLate Lewis acid.