Photochemical synthesis of aporphines

Abstract

The photolysis of iodo aromatic compounds has been employed as the key step in new synthetic routes to aporphines. Photocyclization of l-(2'-iodobenzyl)-l,2,3,4-tetrahydroisoquinoline hydrochlorides (18, 19, 10, 11) yielded noraporphines 29 and 30 and aporphines 33 and 34 directly. Photocyclization of N-acyl-l-(2'-iodobenxyl)-1,2,3,4-tetrahydroisoquinolines (14-17) followed by hydrolysis gave noraporphines 25-28. Photolysis of urethanes 12 and 13 afforded substituted dehydronoraporphines 23 and 24, and two-step reduction gave (=I=)aporphine (33) and (&)-nuciferine (34). Photolysis of iV-carbophe1ioxy-l-(2'-iodobcnzyl)-1,2,3,4-tetrahydroisoquinolines 20 and 21 followed by one-step reduction afforded good yields of (A=)-aporphine (33) and (*)-nuciferine (34). The routes via photocyclimtion of N-acyl iodo aromatic compounds have yielded oxygenated aporphines and noraporphines in the best yields reported to date.

Photochemische Reaktionen als Schlüsselschritte in der Naturstoffsynthese

“…[36] Beispielhaft erwähnt sei die von Cava et al gewählte Route zur Synthese des (AE )-Dicentrins (30). [37] Durch Bischler-Napieralski-Reaktion wurde aus dem Amid [37] (AE )-Aporphin, [38] (AE )-Nuciferin, [38,39] (AE )-Glaucin, [39] (AE )-Cassamedin, [40] (AE )-Sinomendin, [41] (AE )-Elmerrillicin, [42] Pontevedrin, [43] Cepharadion B [44] und (AE )-Goudotianin. [45] In ähnlicher Weise lassen sich auch Alkaloide herstellen, in denen das Stickstoffatom kein Substituent des Stilbenchromophors ist.…”

Inhaltsstoffe des Verbenaöls. 2. Mitteilung. Caryophyllan‐2,6‐β‐oxid, eine neue Sesquiterpenverbindung aus dem Öl von Lippia citriodora KUNTH

“…Als Ausgangsmaterial zur Herstellung grosserer Mengen von 2 verwendeten wir das aus (-)-Caryophyllen (1) uber das bekannte Caryophyllenepoxid 9 leicht zugangliche Epoxiketon 10 [5], welches auch unter dem Namen Kobuson als Inhaltsstoff von Cyperus rotufidus bekannt ist [6] 2). Kobuson (10) liess sich durch reduktive Eliminierung der Epoxygruppe mit schwach verkupfertem Zink in siedendem Athanol (7) in das nor-Caryophyll-5-en-2-on…”

A Novel Approach to the Pyridoacridine Ring System: Synthesis of the Topoisomerase Inhibitor 13‐Deazaascididemin

“…Palladium acetate‐catalyzed intramolecular biaryl syntheses under CH functionalization have been performed in the synthesis of amaryllidaceae alkaloids, but upon treating 6 under the conditions described in the literature 34, no conversion was obtained at all. An attempted photochemical cyclization under conditions successfully applied to the synthesis of aporphine alkaloids 35 failed to give detectable amounts of pentacyclus 5 , too. Finally, we were able to perform the cyclization reaction through generating an aryl radical by debromination of 6 with tributyltin hydride and azobis(isobutyronitrile) (AIBN) 33, 36.…”