Dihydroxyverbacine (10), a precursor for oxidative phenol coupling. was obtained via (+/-)-buchnerine (14). whose synthesis is described. The oxidizing system hemin (ferriprotoporphyrin IX chloride)/H2O2 promoted intramolecular coupling of 10 to give the alkaloids aphelandrine (1). orantine (2), and chaenorpine (7). The alkaloids were identified by on-line coupled HPLC and atmospheric-pressure chemical-ionization (APCI) mass spectrometry.
Antimony-Templated Macrolactamization of Tetraamino Esters. Facile Synthesis of Macrocyclic Spermine Alkaloids, (±)-Buchnerine, (±)-Verbacine, (±)-Verbaskine, and (±)-Verbascenine