Biomimetic Formation of Macrocyclic Spermine Alkaloids

Abstract

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.

Polyamine alkaloids

“…The ring closure from monocyclic dihydroxyverbacine to aphelandrine and orantine was biomimetically reproduced: treatment of the former with ferriprotoporphin IX/H 2 O 2 to effect phenol oxidation delivered also both alkaloids in vitro. 71 The complexation properties of the linear N 1 -cinnamoylspermine, the monocyclic polyazamacrolactam protoverbine, and the macrooligocyclic aphelandrine were recently studied by Déschamps et al by means of ESI-MS. 72 While the open-chain polyamine derivative forms complexes with all investigated dblock cations (Mn 2+ , Co 2+ , Ni 2+ , Cu 2+ , and Zn 2+ ) almost with no discrimination, the polyaza-monocyclic protoverbine shows higher selectivity, ligating solely Ni 2+ and Cu 2+ . The polycyclic aphelandrine proved almost entirely devoid of complexation ability, which is obviously due to the sterically hindered molecular cavity.…”

Asymmetric Syntheses of the Macrocyclic Spermine Alkaloids (−)-(S)-Protoverbine, (−)-(S)-Buchnerine, and Their Naturally Occurring Congenial Alkaloids

“…Photoisomerization of ()-(S)-verbamekrine (23) and ()-(S)-verbasikrine (26) by irradiation of a MeOH soln. at 365 nm led to almost quantitative formation of ()-(S)-isoverbamekrine (24) and (À)-(S)-isoverbasikrine (25).…”

Functionalisation of Macroheterocycles with Preserving and Changing Their Sizes

“…The presence of additional functional groups at one or several nitrogen atoms broadens chelating properties and allows regulating solubility and behaviour in solutions. [22][23][24][25][26][27] N-Functionalized triazamacrocycles that are prepared mostly by N-alkylation reaction [28][29][30][31] are especially attractive compounds to prepare selective ligands that coordinate transition metals.…”