Asymmetric Synthesis of the Corynantheine Alkaloids via an Intramolecular Blaise Reaction. (-)-Corynantheidol and (-)-Dihydrocorynantheol

Article abstract of DOI:10.1021/jo00006a024

An asymmetric total synthesis of the corynantheine family of alkaloids has been accomplished, leading to corynantheidol (1a) and dihydrocorynantheol (1b).Formal synthesis to corynantheidine and dihydrocorynantheine are also shown.The key to this asymmetric route is the use of (1) chiral β-carboline formamidines, which allow high degrees of diastereoselection at C-3 with chloroacetonitrile, and (2) a new version of the Blaise reaction using Zn-Ag couple and ultrasonic radiation.These two synthetic techniques combine to allow an efficient entry into the title compounds.The overall yield of 1a was 16.4percent in seven steps from starting carboline 5.