Synthetic Studies on Lythraceae Alkaloids. III. Stereoselective Total Synthesis of (±)-Decaline

Abstract

The first stereoselective total synthesis of one of Lythraceae alkaloids, decaline, was described. The Mannich condensation of isopelletierine (III) with 6-bromoisovanillin (IV) afforded stereoselectively the trans quinolizidine (V) which was converted to the methyl ether (VI). Stereoselective reduction of VI with the Henbest catalyst gave the axial alcohol (VII) along with the equatorial alcohol (VIII). The Ullmann condensation of the acetyl derivative (IX) from VII with the ester (XI) furnished the biphenyl ether (XII). Hydrolysis of XII and lactonization of the resulting hydroxy-acid (XIV) provided (±)-decaline (II).