β‐Carboline alkaloids 9 [1]. Total synthesis of the β‐carboline alkaloids arenarine A and (±)arenarine B

Bracher, Franz; Puzik, Andreas

doi:10.1002/jhet.5570410206

Cited by 12 publications

(6 citation statements)

References 15 publications

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“…Compound 3 is an alkaloid named arenarine A from the Chinese plant Arenaria kansuensis, and the first total synthesis of 3 was reported by our group some time ago. 5 Having the precursor 3 in hand, we were able to prepare 5-methoxycanthin-4-one (1) in a one-pot reaction. Thus, a solution of 3 in anhydrous DMF was heated with a slight excess of Bredereck's reagent (tert-butoxybis(dimethylamino)methane) to give the desired canthin-4-one 1 in almost quantitative yield.…”

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Revised Structure of the Alkaloid Drymaritin

2009

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In 2004, a new anti-HIV alkaloid named drymaritin was isolated from Drymaria diandra. The authors identified the alkaloid as 5-methoxycanthin-4-one on the basis of spectroscopic data. Here we describe a synthetic approach that unambiguously gave 5-methoxycanthin-4-one, but the synthetic product showed spectroscopic data significantly different from those of the Drymaria alkaloid. Extensive re-evaluation of the spectroscopic data published for this and related alkaloids has led to the conclusion that drymaritin does not have a canthin-4-one backbone, but is identical to the known alkaloid cordatanine (4-methoxycanthin-6-one).

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“…Taking into consideration that drymaritin might be a canthin-6one with a molecular formula of C 15 H 10 N 2 O 2 , only two structures made sense: the above-mentioned 4-methoxy-canthin-6-one ( 4) and 5-methoxycanthin-6-one (5). Compound 5 is also a well-known secondary metabolite from various plants.…”

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Revised Structure of the Alkaloid Drymaritin

2009

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“…However, the unsatisfactory separation of 1-methylisoquinoline intermediate 4 from its unmethylated precursor 3 rendered this protocol unattractive. This is a problem that is common to numerous methylation protocols, including methylation of metalated arenes [16], methylation of arenes bearing directing groups with methylmagnesium bromide [17], and direct methylation using radical reactions [9,18–19]. …”

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confidence: 99%

Aminomethylation/hydrogenolysis as an alternative to direct methylation of metalated isoquinolines – a novel total synthesis of the alkaloid 7-hydroxy-6-methoxy-1-methylisoquinoline

Melzer

Felber

Bracher

2018

Beilstein J. Org. Chem.

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Highly-substituted isoquinolines are important scaffolds in syntheses of natural products and in drug development and hence, effective synthetic approaches are required. Here we present a novel 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 with Eschenmoser's reagent gives an easy to clean tertiary benzylamine, which, after quaternization with iodomethane, is easily converted into the desired 1-methylisoquinoline by hydrogenolysis of both the benzylamine and benzyl ether groups. 130

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“…Starting from known, readily available bromoacetyl‐β‐carboline 16 , the target compound 15 was available in three operations. A nucleophilic substitution with KCN in DMF gave the cyanoketone 17 .…”

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Canthin‐4‐ones as Novel Antibacterial Agents

Tremmel

Puzik

Gehring

et al. 2016

Archiv der Pharmazie

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Based on the chemotype of canthin‐4‐one alkaloids with moderate antimicrobial activity, a collection of variously substituted canthin‐4‐ones and desaza analogs were synthesized. Key steps in the syntheses were regioselective halogenations of (desaza) canthin‐4‐one, followed by Pd‐catalyzed cross‐coupling reactions. The in vitro screening for antimicrobial activity revealed that two 5‐substituted canthin‐4‐ones (3‐pyridyl, 2‐bromophenyl) exhibit significant activity against Streptococcus entericus, coupled with high selectivity and the lack of cytotoxicity against mammalian cells. The intact canthin‐4‐one ring system was demonstrated to be essential for antibacterial activity.

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β‐Carboline alkaloids 9 [1]. Total synthesis of the β‐carboline alkaloids arenarine A and (±)arenarine B

Cited by 12 publications

References 15 publications

Revised Structure of the Alkaloid Drymaritin

Revised Structure of the Alkaloid Drymaritin

Aminomethylation/hydrogenolysis as an alternative to direct methylation of metalated isoquinolines – a novel total synthesis of the alkaloid 7-hydroxy-6-methoxy-1-methylisoquinoline

Canthin‐4‐ones as Novel Antibacterial Agents

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