Arbeitskreis Lindel

Marine Naturstoffe - Bausteine des Lebens

Have you thought about organic synthesis lately?


Aktuelles Gruppenbild vom Arbeitskreis Lindel
 

 

Aktuelle Publikationen:

N. Marsch, M. Kock, T. Lindel, Study on the synthesis of the cyclopenta[f]indole core of raputindole A", Beilstein J. Org. Chem. 2016, 12, 334–342.

 
 
Inhalt:
The raputindoles from the rutaceous tree Raputia simulans share a cyclopenta[f]indole partial structure the synthesis of which is subject of this investigation. An efficient route to a series of 1,5-di(indol-6-yl)pentenones was developed via Mo/Au-catalyzed Meyer–Schuster rearrangement of tertiary propargylic alcohol precursors. However, none of the enones underwent the desired Nazarov cyclization to a cyclopenta[f]indole. More suitable were 6-hydroxyallylated indolines which gave good yields of cyclopenta[f]indolines after treatment with SnCl4, as soon as sterically demanding β-cyclocitral adducts were reacted. Most successful were Pt(II) and Au(I)-catalyzed cyclizations of N-TIPS-protected indolin-6-yl-substituted propargylacetates which provided the hydrogenated tricyclic cyclopenta[f]indole core system in high yield.

A. Frichert, P. G. Jones, T. Lindel, "Enantioselektive Totalsynthese der Terreumole A und C aus dem Pilz Tricholoma terreum", Angew. Chem. 2016, 128, 2969-2972; Angew. Chem. Int. Ed. 2016, 55, 2916-2919.

 
 
Inhalt:
Erstmals gelang die enantioselektive Totalsynthese der cytotoxischen Meroterpenoide Terreumol A und C aus dem Gemeinen Erd-Ritterling Tricholoma terreum. Schlüsselschritt ist der Aufbau des zehngliedrigen Rings durch Olefinmetathese zur trisubstituierten Z-Doppelbindung des [8.4.0]-Bicyclus, die nur in Abwesenheit freier Hydroxygruppen gelang. (−)-Terreumol C wurde vollständig diastereoselektiv in das Bisepoxid (−)-Terreumol A überführt, das somit ausgehend von 2-Brom-3,4-dimethoxybenzaldehyd in 14 Stufen und einer Gesamtausbeute von 23 % erhalten wurde. Eine Röntgenstrukturanalyse des p-Benzochinon-Analogons von (−)-Terreumol A bestätigt die absolute Konfiguration der Naturstoffe.

T. C. Allmann, R.-P. Moldovan, P. G. Jones, T. Lindel, "Synthesis of Hydroxypyrrolone Carboxamides Employing Selectfluor", Chem. Eur. J. 2016, 22, 111-115.

 
 
Inhalt:
Reaction of pyrrole-2-carboxamides with Selectfluor in MeCN/water (4:1) affords 2-hydroxy-5-oxopyrrole-2-carboxamides in yields of up to 80 %. A variety of sensitive functional groups is tolerated, among them aldehydes and alkynes. The new method also works in the presence of allyl groups and appears to be superior to the use of singlet oxygen. Reaction of the monobrominated dihydropyrrolo[1,2-a]pyrazinone mukanadin C and its nonbrominated analogue afforded bicyclic hydroxypyrrolones. These compounds are interesting as they constitute a partial structure of the marine natural product oxocyclostylidol.