Pictet-Spengler Tetrahydroisoquinoline Synthesis

In 1911, A. Pictet and T. Spengler condensed phenylethylamine and dimethoxymethane in concentrated hydrochloric acid to give 1,2,3,4-tetrahydroisoquinoline. They also observed a similar reaction when tyrosine and phenylalanine were treated in the same way. Since then, the condensation of a beta-arylethylamine with a carbonyl compound in the presence of a protic or Lewis acid to create a substituted tetrahydroisoquinoline has been known as the Pictet-Spengler tetrahydroisoquinoline synthesis, or the Pictet-Spengler reaction.

A variation of the Pictet-Spengler reaction utilizes an indole as the aromatic substrate. P.D. Bailey accomplished the total synthesis of the alkaloid (-)-suaveoline using this approach.

Total synthesis of the natural product pyranonaphthoquinone was also accomplished utilizing the Pictet-Spengler reaction to generate the precursor naphthopyran intermediate.