Pictet-Spengler phenolic condensation

F-L (Fig. 2). The Friedel-Crafts reaction (limited in the 1-benzazepine series), Dieckmann, acyloin, and aldol condensations, Bischler-Napieralski, Vilsmeyer, and Pictet-Spengler-type reactions, and phenolic oxidative... 

All major pathways toward tyrosine-derived secondary metabolites discussed within the biosynthetic section of this chapter are summarized in Scheme 12.16. The great structural diversity of this important class of natural products arises from a very limited set of chemical transformations. Except for the extremely simple catecholamines and phenyl-ethylamines, tyrosine-derived alkaloids are generally formed via condensation of two aromatic substrates, facultatively followed by a Pictet-Spengler-type ring closing reaction. Next, the key oxidative phenolic coupling reaction then introduces stractural complexity and serves as convenient tool for the elaboration of different alkaloid frameworks. 

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