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Synthesis of the indeno[1,2- b]indole core of janthitrem B. Org Biomol Chem 2023; 21:9065-9069. [PMID: 37937993 DOI: 10.1039/d3ob01566a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2023]
Abstract
The tetracyclic core structure of the majority of indole diterpenoids features a trans-hydrindane moiety that is fused to an indole unit. We report here a novel synthetic route that includes a photo-Nazarov cyclization of a 3-acylindole precursor initially providing the thermodynamically preferred cis-hydrindanone. After reduction and conversion to the cyclopentadiene, dihydroxylation and hydrogenation provided the indoline. The key step generated the trans-system by stereospecific hydride shift on a dioxaphospholane under Grainger's conditions, for the first time applied to an N-heterocycle. When starting from the corresponding indole, we observed the formation of hitherto unknown methanocyclohepta[b]indolones. Deoxygenation of the trans-hydrindanone was achieved after conversion to the 1,3-dithiolane, followed by RANEY® Ni reduction.
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Azido and desamino analogs of the marine natural product oroidin. ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES 2023. [DOI: 10.1515/znb-2023-0305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/11/2023]
Abstract
Abstract
As part of our program on the synthesis and reactivity of the pyrrole-imidazole alkaloids from marine sponges, the synthesis of the 2-azido analog of the key marine natural product oroidin is reported. In addition, desaminooroidin and its alkyne analog were synthesized. Red-Al reduction of a 4-alkynylimidazole intermediate afforded the (E)-alkene, without having to pass via the (Z)-alkene. Coupling of 4,5-dibromopyrrole-2-carboxylic acid with 2-azidoimidazolylprop-2-en-1-amine was best achieved by EDCI-mediated coupling, which was superior to using the corresponding trichloromethylketone. Use of t-BuOK in acetonitrile can be recommended for the coupling of non-azidated alkenyl and alkynylimidazoles. The azido analog of oroidin underwent click cycloadditions to imidazolyltriazoles.
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Biomimetic Synthesis of Cyanogramides B and C. Org Lett 2022; 24:2479-2482. [PMID: 35333533 DOI: 10.1021/acs.orglett.2c00510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Marinacarboline E and cyanogramides B and C from the marine-derived bacterium Actinoalloteichus cyanogriseus have been synthesized. The key step is the Baeyer-Villiger oxidation of marinacarboline E to a ketene aminal via O → N acetyl migration, followed by addition of water or MeOH. Replacing the phenylethyl by a styryl side chain afforded dehydromarinacarboline E that was oxidized to a tetracyclic aminal. This study contributes to the chemical understanding of the enzymatic conversions in the biosynthesis of the cyanogramides.
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Abstract
The marine natural product ageladine A was synthesized by exploiting novel aza-BODIPY-type boron complexes that allowed the regioselective dibromination of the pyrrole unit, as confirmed by quantum chemical calculation (ωB97XD/TApr-cc-pVDZ). The parent tricycle was accessed by Suzuki-Miyaura cross-coupling employing Buchwald's precatalyst. The boron complex of ageladine A exhibited strong fluorescence that was greater than that of the natural product by a factor of ∼30 and that disappeared in the presence of 2-azido groups.
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Synthesis of pyranocyclopentaindolines representing the western sections of janthitrem B, JBIR‐137, and shearinine G. European J Org Chem 2022. [DOI: 10.1002/ejoc.202101454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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6
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Incorporation of 4J-HMBC and NOE Data into Computer-Assisted Structure Elucidation with WebCocon. Molecules 2021; 26:molecules26164846. [PMID: 34443433 PMCID: PMC8398166 DOI: 10.3390/molecules26164846] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Revised: 06/24/2021] [Accepted: 06/25/2021] [Indexed: 01/13/2023] Open
Abstract
Over the past decades, different software programs have been developed for the Computer-Assisted Structure Elucidation (CASE) with NMR data using with various approaches. WebCocon is one of them that has been continuously improved over the past 20 years. Here, we present the inclusion of 4JCH correlations (4J-HMBC) in the HMBC interpretation of Cocon and NOE data in WebCocon. The 4J-HMBC data is used during the structure generation process, while the NOE data is used in post-processing of the results. The marine natural product oxocyclostylidol was selected to demonstrate WebCocon’s enhanced HMBC data processing capabilities. A systematic study of the 4JCH correlations of oxocyclostylidol was performed. The application of NOEs in CASE is demonstrated using the NOE correlations of the diterpene pyrone asperginol A known from the literature. As a result, we obtained a conformation that corresponds very well to the existing X-ray structure.
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Di‐ and Trifluorinated 2‐Azidobenzimidazole Derivatives: Synthesis, Photooxygenation, and
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F NMR Prediction. European J Org Chem 2021. [DOI: 10.1002/ejoc.202100603] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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8
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Synthesis of (−)‐Dihydroraputindole D by Enantioselective Benzoylation of a 1,3‐Diol Intermediate. Chemistry 2020; 26:12733-12737. [PMID: 32725857 PMCID: PMC7590097 DOI: 10.1002/chem.202002579] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Indexed: 11/10/2022]
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9
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Insights into the Cnx1E catalyzed MPT-AMP hydrolysis. Biosci Rep 2020; 40:BSR20191806. [PMID: 31860061 PMCID: PMC6954367 DOI: 10.1042/bsr20191806] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 12/17/2019] [Accepted: 12/19/2019] [Indexed: 11/23/2022] Open
Abstract
Molybdenum insertases (Mo-insertases) catalyze the final step of molybdenum cofactor (Moco) biosynthesis, an evolutionary old and highly conserved multi-step pathway. In the first step of the pathway, GTP serves as substrate for the formation of cyclic pyranopterin monophosphate, which is subsequently converted into molybdopterin (MPT) in the second pathway step. In the following synthesis steps, MPT is adenylated yielding MPT-AMP that is subsequently used as substrate for enzyme catalyzed molybdate insertion. Molybdate insertion and MPT-AMP hydrolysis are catalyzed by the Mo-insertase E-domain. Earlier work reported a highly conserved aspartate residue to be essential for Mo-insertase functionality. In this work, we confirmed the mechanistic relevance of this residue for the Arabidopsis thaliana Mo-insertase Cnx1E. We found that the conservative substitution of Cnx1E residue Asp274 by Glu (D274E) leads to an arrest of MPT-AMP hydrolysis and hence to the accumulation of MPT-AMP. We further showed that the MPT-AMP accumulation goes in hand with the accumulation of molybdate. By crystallization and structure determination of the Cnx1E variant D274E, we identified the potential reason for the missing hydrolysis activity in the disorder of the region spanning amino acids 269 to 274. We reasoned that this is caused by the inability of a glutamate in position 274 to coordinate the octahedral Mg2+-water complex in the Cnx1E active site.
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Synthesis of the polyketide section of seragamide A and related cyclodepsipeptides via Negishi cross coupling. Beilstein J Org Chem 2019; 15:577-583. [PMID: 30873243 PMCID: PMC6404460 DOI: 10.3762/bjoc.15.53] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Accepted: 02/12/2019] [Indexed: 01/22/2023] Open
Abstract
The synthesis of the polyketide section present in the potently cytotoxic marine cyclodepsipeptide jasplakinolide and related natural products, geodiamolides and seragamides, is reported. The key step is a Negishi cross coupling of (R)-(3-methoxy-2-methyl-3-oxopropyl)zinc(II) bromide and an (E)-iodoalkene that was synthesized via an aluminium ester enolate attack at (R)-propylene oxide. The overall synthesis comprises nine steps with an overall yield of 21%. It proved to be possible to liberate the free 8-hydroxynonenoic acid and to couple it with a protected tripeptide composed of L-alanine, N,O-dimethyl-D-iodotyrosine, and TIPS-protected L-threonine, which occurs as partial structure of seragamide A. The tripeptide section of seragamide A was assembled by solution-phase synthesis and an open-chain analogue of the natural product was obtained.
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Congratulations to Professor Wolfgang Bensch on the occasion of his 65th birthday. ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES 2019. [DOI: 10.1515/znb-2018-0221] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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13
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Tackling the Spiro Tetracyclic Skeleton of Cyanogramide: Incorporation of a Hydantoin Moiety. Org Lett 2018; 20:7969-7972. [DOI: 10.1021/acs.orglett.8b03540] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Congratulations to Bernt Krebs. ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES 2018. [DOI: 10.1515/znb-2018-0126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Congratulations to Werner Uhl. ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES 2018. [DOI: 10.1515/znb-2018-0127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Abstract
The synthesis of the macrocyclic core of the cytotoxic natural product salarin C from the sponge Fascaplysinopsis sp. is described, with the two epoxides being replaced by alkene moieties. In the key step, ring-closing metathesis exclusively afforded the ( E)-product. NOESY-based conformational analysis of the macrolactone showed that the oxazole ring and its unsaturated side chains are located in a common plane. Mimicking the conversion of salarin C to salarin A, the trisubstituted oxazole unit embedded in the 17-membered ring underwent photooxidation on treatment with singlet oxygen, affording macrocyclic trisacylamines.
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Synthesis of eunicellane-type bicycles embedding a 1,3-cyclohexadiene moiety. Beilstein J Org Chem 2018; 14:2461-2467. [PMID: 30344769 PMCID: PMC6176824 DOI: 10.3762/bjoc.14.222] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2018] [Accepted: 09/05/2018] [Indexed: 11/23/2022] Open
Abstract
The first synthesis of diterpenoid eunicellane skeletons incorporating a 1,3-cyclohexadiene moiety is presented. Key step is a low-valent titanium-induced pinacol cyclization that proved to be perfectly diastereoselective. Determination of the relative configuration of the diol was aided by the conversion to the diastereomer by oxidation and reduction. Conformational analysis of some of the resulting diols obtained under McMurry conditions was complicated by the presence of several conformers of similar energy. The pinacol coupling appears to start at the ketone, as indicated by the selective reduction of non-cyclizing cyclohexane systems that were synthesized from limonene oxide. The title compounds and their synthetic precursors are prone to aromatization on contact with air oxygen. Attempted synthesis of cyclohexene-containing eunicellane bicycles by elimination of water from tertiary alkynyl carbinols afforded novel allene systems. Our study may be of help towards the total synthesis of solenopodin or klysimplexin derivatives.
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Abstract
The first total synthesis of the bisindole alkaloid raputindole A from the rutaceous plant Raputia simulans is reported. The key step is a Au(I)-catalyzed cyclization that assembles the cyclopenta[f]indole tricycle from a 6-alkynylated indoline precursor. The isobutenyl side chain was installed by Suzuki-Miyaura cross-coupling, followed by a regioselective reduction employing LiDBB. Starting from 6-iodoindole, the sequence needs nine steps and provided (±)-raputindole A in 6.6% overall yield. The absolute configuration of the natural product (+)-raputindole A was determined by quantum chemical calculation of the ECD spectrum.
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Oxidation of the Meroterpenoid (-)-Terreumol C from the Mushroom Tricholoma terreum: Discovery of Cytotoxic Analogues. JOURNAL OF NATURAL PRODUCTS 2017; 80:2652-2658. [PMID: 28956915 DOI: 10.1021/acs.jnatprod.7b00236] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Aiming at the discovery of new cytotoxic meroterpenoids, the chemical reactivity of the natural product (-)-terreumol C from the edible mushroom Tricholoma terreum was investigated. A series of high-yielding oxygenations and brominations at the 10-membered ring were discovered. The regioselectivity of hydroxylation could be guided by installing protecting groups at the hydroquinone section. Dihydroxylation led to the stereoselective formation of a novel tricycle containing an 11-oxabicyclo[5.3.1]undecane system. Several of the compounds proved to be as cytotoxic against cancer cell lines as the natural products terreumols A and C in the single-digit micromolar range. Interestingly, functionalization of the southern rim formed by carbons C5-C6-C7-C8 is tolerated without much loss of cytotoxicity.
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Congratulations to Dietrich Gudat. ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES 2017. [DOI: 10.1515/znb-2017-0142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Total Synthesis of the Marine Natural Product Hemiasterlin by Organocatalyzed α-Hydrazination. Chemistry 2017; 23:12714-12717. [DOI: 10.1002/chem.201702812] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Indexed: 11/07/2022]
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Abstract
An efficient synthesis of the molybdopterin/molybdenum cofactor (Moco) oxidation product dephospho Form A is described that assembles the pteridinone system starting from an iodinated aminopyrazine. The sodium salt of dephospho Form A could be purified by precipitation from methanol, which paved the way to the title compound in the 100 mg range. By HPLC, the synthetic material was compared with a sample isolated from a recombinant Moco containing protein. Analysis of dephospho Form A is the only method that allows the quantification of the Moco content of crude cell extracts and recombinant protein preparations.
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Synthesis and Photooxidation of the Trisubstituted Oxazole Fragment of the Marine Natural Product Salarin C. Org Lett 2017; 19:2306-2309. [PMID: 28425712 DOI: 10.1021/acs.orglett.7b00845] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The eastern section of the macrocyclic marine natural product salarin C from the sponge Fascaplysinopsis sp. was synthesized employing a halogen dance reaction to assemble the trisubstituted oxazole moiety. The synthesis was inspired by Kashman's hypothesis on the biomimetic oxidation of salarin C to salarin A. Clean conversion to the triacylamine partial structure of salarin A occurred on treatment with photochemically generated singlet oxygen. Thus, a Wasserman-type oxidative rearrangement is chemically possible in this case.
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Chemistry and Biology of the Pyrrole–Imidazole Alkaloids. THE ALKALOIDS: CHEMISTRY AND BIOLOGY 2017; 77:117-219. [DOI: 10.1016/bs.alkal.2016.12.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Photoreactivity of monofluorinated 2-azidobenzimidazoles towards carboxylic acids. ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES 2016. [DOI: 10.1515/znb-2016-0195] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Aiming at the development of new photolabeling agents, the synthesis and photoreactivity of all monofluorinated derivatives of 2-azido-1-methylbenzimidazole are described. In the case of 4-, 5-, or 7-fluorination, irradiation in the presence of carboxylic acids (300 nm, Rayonet) afforded the monofluorinated 2-amino-6-acyloxybenzimidazoles in a regioselective manner, presumably after conversion of the initially formed nitrene to the N-cyanodiazaxylylene. Incorporation of chloride was also possible, and yields were comparable to those observed for the non-fluorinated parent compound. When blocking the reactive 6-position by a fluoro substituent, the title reaction was not possible. The analysis of the 19F NMR chemical shifts of the 5- and 7-monofluorinated products allowed the distinction between carboxylates and other nucleophiles.
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Congratulations to Gerhard Erker. ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES 2016. [DOI: 10.1515/znb-2016-0177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Congratulations to Wolfgang Jeitschko. ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES 2016. [DOI: 10.1515/znb-2016-0052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Study on the synthesis of the cyclopenta[f]indole core of raputindole A. Beilstein J Org Chem 2016; 12:334-42. [PMID: 26977193 PMCID: PMC4778506 DOI: 10.3762/bjoc.12.36] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 02/05/2016] [Indexed: 12/04/2022] Open
Abstract
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.
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Enantioselektive Totalsynthese der Terreumole A und C aus dem Pilz Tricholoma terreum. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201510709] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Enantioselective Total Synthesis of Terreumols A and C from the Mushroom Tricholoma terreum. Angew Chem Int Ed Engl 2016; 55:2916-9. [DOI: 10.1002/anie.201510709] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Indexed: 11/09/2022]
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Synthesis of Hydroxypyrrolone Carboxamides Employing Selectfluor. Chemistry 2015; 22:111-5. [DOI: 10.1002/chem.201503695] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Indexed: 01/25/2023]
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SmI2-mediated dimerization of indolylbutenones and synthesis of the myxobacterial natural product indiacen B. Beilstein J Org Chem 2015; 11:1700-6. [PMID: 26664588 PMCID: PMC4660955 DOI: 10.3762/bjoc.11.184] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 08/31/2015] [Indexed: 01/14/2023] Open
Abstract
The synthesis and reactivity of indole derivatives substituted in the benzene section was studied. Starting materials 4- and 6-iodoindole were conveniently prepared via the Batcho–Leimgruber route and purified by sublimation. Novel vicinally indolyl-substituted cyclopentanols with unexpected cis-configuration were formed by SmI2-mediated reductive dimerization of a 4-(indol-6-yl)butenone, obtained by Heck reaction. The two indolyl units appear to chelate Sm(II)/(III) leading to a gauche-type arrangement at the newly formed bond between the two β-carbons. Through a sequence of Sonogashira cross coupling and Meyer–Schuster rearrangement 6-prenoylindole was synthesized and reductively dimerized to a cyclopentane in a [3 + 2] cycloaddition by treatment with SmI2 in THF. From 4-iodoindole, the natural product indiacen B from the myxobacterium Sandaracinus amylolyticus was synthesized for the first time, confirming its antimicrobial activity. The E-configuration of the chloroalkene moiety of indiacen B was confirmed by X-ray analysis.
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Total Synthesis of the Marine Natural Product Parazoanthine F by Copper-Mediated C-N Coupling. European J Org Chem 2015. [DOI: 10.1002/ejoc.201500823] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Enantioselective Synthesis and Photoreactivity of a Diazirinyl-substituted (R)-β-Phenylalanine. ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES 2015. [DOI: 10.5560/znb.2014-4152] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Abstract
The first enantioselective synthesis of a photoreactive (R)-β-phenylalanine is described. In the key step, m-diazirinyl-substituted benzaldehyde is converted to a chiral sulfinimine in a Ti(OEt)4- mediated reaction, followed by diastereoselective enolate addition. The absolute configuration of photo (R)-β-phenylalanine was confirmed by Mosher analysis. The photo amino acid proved to be thermally stable under standard laboratory conditions. Irradiation in toluene afforded cycloheptatriene=norcaradiene valence tautomers, together with carbene benzylation. Quantumchemical calculations indicate a small triplet-singlet gap.
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Zeitschrift für Naturforschung B now being published by De Gruyter. ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES 2015. [DOI: 10.1515/znb-2014-1000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Abstract
A novel photoarylation of amino acids and peptides is described, which tolerates the presence of water. Irradiation of Boc-protected amino acids in the presence of N-protected 2-azidobenzimidazoles leads to selective arylation of carboxy termini or side chains. The new reaction also works for peptides. Irradiation of the nonapeptide H-SPSYVYHQF-OH also resulted in selective arylation of the tyrosine side chains, as indicated by ESI-MS/MS fragmentation. Chemo- and regioselectivity could add the title reaction to the repertoire of photoaffinity labeling methods.
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Synthesis, Stability, and Photoreactivity of Diazirinyl-SubstitutedN-Heterocycles Based on Indole, Benzimidazole, and Imidazole. European J Org Chem 2014. [DOI: 10.1002/ejoc.201402354] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Skeleton Diversity by Cyclopropanation of Tricyclic Acylenamines. ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES 2014. [DOI: 10.1515/znb-2009-0605] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Aiming at the structural diversification of phakellin- and isophakellin-type pyrrole-imidazole alkaloids on the skeleton level, the reaction of dipyrrolopyrazinones and pyrroloindolizines with dichlorocarbene was investigated. Conversions resulted in ring expansion affording novel chlorinated and brominated dipyrroloazepinones, pyridopyrroloazepinones, and dipyrrolopyrazinones. Structures of the tetracyclic products with hitherto unknown architectures have been secured by X-ray analyses.
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Synthesis of the Pyrrole-Imidazole Alkaloid Sventrin from the Marine Sponge Agelas sventres. ACTA ACUST UNITED AC 2014. [DOI: 10.1515/znb-2003-0516] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The marine pyrrole-imidazole alkaloid sventrin (1) and the hitherto unknown dehydrooroidin (3) have been synthesized stereoselectively via alkyne intermediates. The pathways start from a 2-azido-4-alkynylimidazole which can be chemo- and stereoselectively reduced to the corresponding amino alkene using NaAlH2(OCH2CH2OMe)2 (Red-Al) or, alternatively, to the amino alkyne. Selective removal of simultaneously present Boc or trityl protecting groups was possible employing either p-TsOH or acetic resp. formic acid.
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Abstract
Dihydrooroidin was converted to the marine natural product oroidin in 75% overall yield by chlorination of the 2-aminoimidazole unit in DMF, followed by dehydrochlorination. The natural product ugibohlin was synthesized for the first time by ring opening of dibromoisophakellin, which was obtained in a quantitative manner by heating the free base of dibromophakellin in neutral aqueous solution
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Total synthesis and cytotoxicity of the marine natural product malevamide D and a photoreactive analog. Beilstein J Org Chem 2014; 10:316-22. [PMID: 24605152 PMCID: PMC3943603 DOI: 10.3762/bjoc.10.29] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Accepted: 01/03/2014] [Indexed: 11/23/2022] Open
Abstract
The marine natural product malevamide D from the cyanobacterium Symploca hydnoides was synthesized for the first time. The final peptide coupling linked the dolaisoleuine and dolaproine subunits. The phenyl group of malevamide D was also functionalized with a photoreactive diazirine moiety, which was carried through seven reaction steps. Comprehensive assessment of the cytotoxicity in a panel of 42 human cancer cell lines revealed a geomean IC70 value of 1.5 nM (IC50 0.7 nM) for malevamide D, whereas the photoreactive derivative proved to be less active by a factor of at least 200. COMPARE analysis indicated tubulin interaction as likely mode of action of malevamide D.
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Synthesis of a 30-Membered Macrocycle Incorporating Two Ruthenium Sandwich Complexes. ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES 2013. [DOI: 10.5560/znb.2013-3067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The first macrocycle incorporating two ruthenium sandwich complexes has been synthesised. Key step is a cyclodimerisation by double etherification of a p-chlorophenylalanine-derived [RuCp*]+ complex. Silica-based cation exchange chromatography allowed the separation of dicationic diastereomers. Assignment of the relative configurations was possible by X-ray structure determination. Partial demetalation in acetonitrile proceeded in high yield by irradiation in the presence of biphenyl
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Photoactivation of (p-methoxyphenyl)(trifluoromethyl)diazirine in the presence of phenolic reaction partners. Chemistry 2013; 19:6551-5. [PMID: 23553983 DOI: 10.1002/chem.201203479] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Revised: 02/25/2013] [Indexed: 12/15/2022]
Abstract
Shine light on your chemistry! Irradiating 3-(4-methoxyphenyl)-3-(trifluoromethyl)-3H-diazirine in the presence of equimolar solutions of phenol and tyrosine derivatives leads to Friedel-Crafts alkylations (see scheme), which suggests a strategy for the development of "cleaner" diazirines for chemical biology.
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To Professor Alfred Klemm on the Occasion of his 100 thBirthday. ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES 2013. [DOI: 10.5560/znb.2013-2315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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To Professor Heinrich Nöth on the Occasion of his 85 thBirthday. ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES 2013. [DOI: 10.5560/znb.2013-3118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Doubly prenylated tryptamines: cytotoxicity, antimicrobial activity and cyclisation to the marine natural product flustramine A. Org Biomol Chem 2013; 11:6119-30. [DOI: 10.1039/c3ob40896e] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Identification of superoxide production by Arabidopsis thaliana aldehyde oxidases AAO1 and AAO3. PLANT MOLECULAR BIOLOGY 2012; 80:659-71. [PMID: 23065119 DOI: 10.1007/s11103-012-9975-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Accepted: 09/28/2012] [Indexed: 05/07/2023]
Abstract
Plant aldehyde oxidases (AOs) have gained great attention during the last years as they catalyze the last step in the biosynthesis of the phytohormone abscisic acid by oxidation of abscisic aldehyde. Furthermore, oxidation of indole-3-acetaldehyde by AOs is likely to represent one route to produce another phytohormone, indole-3-acetic acid, and thus, AOs play important roles in many aspects of plant growth and development. In the present work we demonstrate that heterologously expressed AAO1 and AAO3, two prominent members of the AO family from Arabidopsis thaliana, do not only generate hydrogen peroxide but also superoxide anions by transferring aldehyde-derived electrons to molecular oxygen. In support of this, superoxide production has also been found for native AO proteins in Arabidopsis leaf extracts. In addition to their aldehyde oxidation activity, AAO1 and AAO3 were found to exhibit NADH oxidase activity, which likewise is associated with the production of superoxide anions. According to these results and due to the fact that molecular oxygen is the only known physiological electron acceptor of AOs, the production of hydrogen peroxide and/or superoxide has to be considered in any physiological condition in which aldehydes or NADH serve as substrate for AOs. In this respect, conditions such as natural senescence and stress-induced stomatal movement, which both require simultaneously elevated levels of abscisic acid and hydrogen peroxide/superoxide, are likely to benefit from AOs in two ways, namely by formation of abscisic acid and by concomitant formation of reactive oxygen species.
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