General approach for the total synthesis of the sarpagine related indole alkaloids (+)- Na-methyl-16-epipericyclivine, (−)-alkaloid Q 3 and (−)-panarine via the asymmetric Pictet–Spengler reaction

Abstract

The stereospecific total synthesis of (+)- N a-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, CHCl 3)} obtained on this material confirmed that the reported optical rotation {[ α] D 0 ( c 0.50, CHCl 3)} [] was biogenetically unreasonable. The first total synthesis of (−)-alkaloid Q 3 ( 5 ) and (−)-panarine ( 6 ), via the intermediate vellosimine ( 18 ), is also described.