Synthetic study of (-)-norzoanthamine: construction of the ABC ring moiety.

Throw your hat in the ring: A highly diastereoselective synthesis of the ABC rings of (-)-norzoanthamine has been achieved starting from the (-)-Hajos-Parrish ketone (see scheme). Three asymmetric quaternary carbon centers on the C ring were constructed by a 1,4-addition, and an intramolecular Diels-Alder reaction provided a trans-decalin scaffold on the AB rings.