Formation of the C6-NC-20 bridge for entry into the hetisane skeleton

As a result of recent investigations into the total synthesis of the complex diterpene alkaloid nominine, the preparation of two new heterocyclic intermediates is now described. The cyclic ether 10 was derived from an intramolecular Mitsunobu reaction. The precursor hydroxylated compound 9 was the minor product of the hydroboration of alkene 7, which proceeded with an unexpected stereochemical outcome. The lactam 3 was derived from the hydrogenation of oxime 18 through presumed cyclization of the amino ester.