First enantioselective total synthesis of neocarazostatin B, determination of its absolute configuration and transformation into carquinostatin A

Czerwonka, Regina; Reddy, Kethiri R.; Baum, Elke; Knölker, Hans‐Joachim

doi:10.1039/b515674b

Cited by 72 publications

(36 citation statements)

References 42 publications

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“…The EtOH extract of the mycelial culture was sequentially fractionated with petroleum ether, CHCl 3 , and EtOAc. The EtOAc-soluble extract, by separation with silica gel and Sephadex LH-20 column chromatography, yielded compounds 1 and 2 along with cyclo(leucylprolyl) [5] and a mixture of cyclo(isoleucylleucyl) [6] and cyclo(leucylvalyl) [7], which were identified by interpretation of their spectroscopic (ESIMS, 1 H NMR, and 13 C NMR) data as well as by comparison of their physical and spectroscopic data with those in the indicated literatures.…”

Section: Resultsmentioning

confidence: 99%

“…1 had a molecular formula of C 18 H 21 NO 3 by analysis of its HRTOFMS, 13 C NMR and DEPT data. The 1 H NMR spectrum (see Experimental section) in combination with the COSY spectrum (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…2 had a molecular formula, C 11 H 11 NO 4 , as determined by analysis of its HRTOFMS, ESIMS, and NMR ( 1 H, 13 (Fig. 2) from H-1 and H 2 -3 to C-2, C-4, C-5, and C-6, from H 2 -6 to C-1Ј, C-2Ј, C-6Ј, C-3, C-4, and C-5, and from H-1 to C-3 indicated a connectivity of N-1, C-2, C-3, and C-4 to create a 2-azetidinone ring with a carboxyl group and a phydroxylbenzyl group attached to C-4.…”

Section: Resultsmentioning

confidence: 99%

“…The UV spectra were recorded in MeOH on a Perkin-Elmer Lambda 25 UV-vis spectrophotometer. The 1 H (400 MHz), 13 C (100 MHz), and 2D NMR spectra were recorded on a Bruker DRX-400 instrument using TMS as an internal reference. HRTOFMS data were obtained on an API QSTAR TOF mass spectrometer in positive-ion mode.…”

Section: Generalmentioning

confidence: 99%

See 3 more Smart Citations

Two New Antifungal Alkaloids Produced by Streptoverticillium morookaense

Niu

et al. 2007

J Antibiot

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Section: Resultsmentioning

confidence: 99%

“…1 had a molecular formula of C 18 H 21 NO 3 by analysis of its HRTOFMS, 13 C NMR and DEPT data. The 1 H NMR spectrum (see Experimental section) in combination with the COSY spectrum (Fig.…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Generalmentioning

confidence: 99%

See 2 more Smart Citations

Two New Antifungal Alkaloids Produced by Streptoverticillium morookaense

Niu

et al. 2007

J Antibiot

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“…23 Starting from guaiacol, the enantiopure arylamine 17 was prepared in eight steps and 65% overall yield by using (R)-propene oxide as chiral building block. Thus, stirring a solution of complex salt 7 and the arylamine 17 in air at room temperature afforded the tricarbonyliron-coordinated 4a,9a-dihydro-9H-carbazole 18 as stable compound.…”

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confidence: 99%

Synthesis of Biologically Active Carbazole Alkaloids Using Selective Transition-metal-catalyzed Coupling Reactions

Knölker¹

2008

Chemistry Letters

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194

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Highly convergent syntheses of substituted carbazoles are most conveniently achieved using organometallic chemistry. Construction of the carbazole framework via the iron-mediated route proceeds by a sequence of C-C and C-N bond formation. In the highly efficient palladium-catalyzed route the C-N bond is formed first followed by generation of the C-C bond. This article highlights some recent developments and applications to the total synthesis of biologically active carbazole alkaloids. Ç IntroductionThe chemistry and biology of carbazole alkaloids has attracted an increasing interest over the last 50 years. Important milestones for the tremendous development of this class of natural products were the isolation of ellipticine (1) Since then a broad range of structurally interesting carbazole alkaloids with useful biological activities has been isolated from diverse natural sources.3,4 The pharmacological potential of these natural products initiated the development of novel synthetic methods for efficient routes to carbazoles. 4 We have established an iron-mediated and a palladium-catalyzed route, which are based on transition metal-induced coupling reactions of arylamines. 5 The present article briefly summarizes these achievements and shows recent applications to total synthesis.

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The Chemistry of Diene–Iron and Dienyl–Iron Complexes

Бауер

Knölker

2013

Patai's Chemistry of Functional Groups

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(η 4 ‐Diene)iron complexes and η 5 ‐dienyliumiron complex salts represent intriguing structures with planar π‐donating C 4 or C 5 ligands attached to the central iron atom. In many cases, they are rather stable compounds due to an 18‐electron count at the iron center. Tricarbonyl(η 4 ‐diene)iron complexes are formed from cyclic and acylic 1,3‐dienes and a tricarbonyliron source. Under certain conditions 1,4‐dienes can be employed with concomitant rearragement of the double bonds. The tricarbonyliron source can be a binary carbonyliron complex or a tricarbonyliron transfer reagent. (η 4 ‐1‐Azabutadiene)tricarbonyliron complexes have been proven to transfer the tricarbonyliron unit efficiently to the diene system. 1‐Azabutadiene ligands can even be employed in catalytic amounts. Chiral 1‐azabutadiene ligands enable the catalytic asymmetric synthesis of planar chiral (η 4 ‐diene)iron complexes. The tricarbonyliron fragment in (η 4 ‐diene)iron complexes is shielding one side of the diene system. Thus, it can be utilized to control stereoselective reactions in its proximity. Moreover, due to their stability (η 4 ‐diene)iron complexes can be employed as protected 1,3‐dienes. η 5 ‐Dienyliumiron complexes are generated from (η 4 ‐diene)iron complexes by two principal methods. Either by hydride abstraction at the α‐position of the diene ligand using triphenylcarbenium salts or by elimination of leaving groups adjacent to the diene system. η 5 ‐Dienyliumiron complexes are versatile electrophiles which react with a large variety of nucleophiles leading to functionalized (η 4 ‐diene)iron complexes. In most cases, nucleophilic attack at the terminus of the co‐ordinated dienylium system is preferred. Especially with C‐nucleophiles, the reaction is extremely useful for the construction of natural products or advanced synthetic precursors. Employment of substituted anilines as nucleophiles has paved the way to the total synthesis of a large number of biologically active carbazole alkaloids. After exploiting the activating, protecting or stereodirecting effect of the iron complex, the organic ligand is disengaged from the metal. A variety of mild demetalation procedures has been developed for this purpose. In addition to the stoichiometric reactions, first examples of catalytic applications of (diene)iron complexes are dicussed in this chapter.

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First enantioselective total synthesis of neocarazostatin B, determination of its absolute configuration and transformation into carquinostatin A

Abstract: The first enantioselective total synthesis of neocarazostatin B, the determination of its absolute configuration and transformation into carquinostatin A are described.

Cited by 72 publications

References 42 publications

Two New Antifungal Alkaloids Produced by Streptoverticillium morookaense

Two New Antifungal Alkaloids Produced by Streptoverticillium morookaense

Synthesis of Biologically Active Carbazole Alkaloids Using Selective Transition-metal-catalyzed Coupling Reactions

The Chemistry of Diene–Iron and Dienyl–Iron Complexes

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