General Approach for the Total Synthesis of the Sarpagine Related Indole Alkaloids (+)‐Na‐Methyl‐16‐epipericyclivine, (‐)‐Alkaloid Q3 and (‐)‐Panarine via the Asymmetric Pictet—Spengler Reaction

Abstract

The stereospecific total synthesis of (+)-Na-methyl-16-epipericyclivine (1) was completed [from d-(+)-tryptophan methyl ester] in an overall yield of 42% (eight reaction vessels). The optical rotation {[α]D +22.8 (c 0.50, CHCl3)} obtained on this material confirmed that the reported optical rotation {[α]D 0 (c 0.50, CHCl3)} [] was biogenetically unreasonable. The first total synthesis of (−)-alkaloid Q3 (5) and (−)-panarine (6), via the intermediate vellosimine (18), is also described.