Synthetic studies on Lythraceae alkaloids via (3+2)cycloaddition. II. Total synthesis of (.+-.)-decaline and (.+-.)-vertaline.

Abstract

An efficient total synthesis of (±)-decaline and (±)-vertaline, lactonic biphenyl ether Lythraceae alkaloids, was achieved. The [3+2] cycloaddition of the nitrone (24) with the olefin (10), prepared via the Ullmann reaction catalyzed by a phase-transfer reagent, produced the adduct (11) which, upon treatment with methanesulfonyl chloride followed by reductive cleavage of the N-O bond, gave the isomeric quinolizidinols (13 and 14) in a one-pot operation. Through the use of inter-and intramolecular Mitsunobu reaction as an inversion procedure at C-2, 13 was converted into (±)-decaline (1). On the other hand, the cis-quinolizidinol (14) was transformed in two steps to (±)-vertaline (2).