Protoberberine ausReissert-Verbindungen, 2. Mitt.: Eine neue Synthese von 8-Methyldibenzo[a,g]chinolizidinen
作者:Eberhard Reimann、Helmut Renz
DOI:10.1002/ardp.19933260502
日期:——
Reissert‐Verbindungen 16 werden mit dem Benzylbromid 14 zu den Dihydroisochinolinen 5 benzyliert. Durch alkalische Spaltung bilden sich daraus die 1‐Benzylisochinoline 6, die mit Säure spontan zu den desoxygenierten Coralynen 4 cyclisieren. 4a sowie das aus 4b erhaltene Chinoliziniumsalz 18 werden mit NaBH4 zu den 8‐Methyl‐trans‐dibenzochinolizidinen 19 reduziert. Die Sequenz 5 → 6 → 4 → 19 beinhaltet einen
Aminomethylation/hydrogenolysis as an alternative to direct methylation of metalated isoquinolines – a novel total synthesis of the alkaloid 7-hydroxy-6-methoxy-1-methylisoquinoline
作者:Benedikt C Melzer、Jan G Felber、Franz Bracher
DOI:10.3762/bjoc.14.8
日期:——
method for the introduction of a methyl group at C1 of isoquinolines. This is exemplified by a new total synthesis of the alkaloid 7-hydroxy-6-methoxy-1-methylisoquinoline. Direct metalation of 7-benzyloxy-6-methoxyisoquinoline with Knochel-Hauser base, followed by cuprate-mediated methylation gives the target alkaloid directly, but separation from the educt is cumbersome. Quenching the metalated intermediate
A shorter synthesis of the demethyl(oxy)aaptamine skeleton was developed via oxidativeintramolecular cyclization of 1-(2-azidoethyl)-6-methoxyisoquinolin-7-ol followed by dehydrogenation with a hypervalentiodine reagent. This is the first example of oxidative cyclization at the ortho-position of phenol that does not involve spiro-cyclization, resulting in the improved total synthesis of 3-(phene
Dearomative Access to (−)-Thebaine and Derivatives
作者:Zachary A. Tolchin、Dallas M. Dukes、Leanna M. Gharbaoui、Joel M. Smith
DOI:10.1021/acs.orglett.3c03270
日期:2023.12.1
hinging on the dearomatization and coupling of simple aromatic starting materials. This provides divergent access to two unnatural opioid derivatives and is aimed at the long-term development of synthetic opioid analogs of the “wonderdrug” Naloxone. Additionally, a formal enantioselective synthesis of all reported targets is disclosed that leverages a catalytic asymmetric dearomatization via anion-pairing