Synthetic Studies on Lythraceae Alkaloids. V. Total Synthesis of (±)-Vertaline

Abstract

The first total synthesis of one of the cis-quinolizidine Lythraceae alkaloids, vertaline (IV), was described. The Mannich reaction of isopelletierine (V) with 6-bromoveratraldehyde (VI) in tetrahydrofuran in the presence of aqueous sodium hydroxide gave the cis-and trans-quinolizidine (VII and VIII) in the ratio of 5 : 2. Reduction of VII with sodium borohydride afforded the axial alcohol (IX) along with the equatorial alcohol (X). The Ullmann condensation of the acetyl derivative (XI) from IX with methyl 3-(4-hydroxyphenyl) propionate furnished the biphenyl ether (XIII). Hydrolysis of XIII and lactonization of the resulting hydroxy-acid (XV) provided (±)-vertaline (IV).