The Experts below are selected from a list of 702 Experts worldwide ranked by ideXlab platform
Paul D. Beer - One of the best experts on this subject based on the ideXlab platform.
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active metal template synthesis of a neutral Indolocarbazole containing 2 rotaxane host system for selective oxoanion recognition
Organic and Biomolecular Chemistry, 2017Co-Authors: Asha Brown, Kathleen M Mullen, Thomas Lang, Paul D. BeerAbstract:An active metal template strategy was used to synthesise a neutral Indolocarbazole containing [2]rotaxane anion host system. 1H NMR anion binding investigations reveal that the [2]rotaxane recognises a range of monoanions in acetone-d5 : D2O 95 : 5 with an unusual interlocked host selectivity for acetate and dihydrogenphosphate oxoanions over halides. The rotaxane displays an overall selectivity for the sulfate dianion, favouring a 2 : 1 host : guest binding stoichiometry at low sulfate concentration and a 1 : 1 stoichiometry in the presence of excess sulfate. Fluorescence titration demonstrates that the [2]rotaxane is also capable of sensing guest anions via significant changes in its emission spectrum.
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anion templated assembly of an Indolocarbazole containing pseudorotaxane on beads and silica nanoparticles
New Journal of Chemistry, 2009Co-Authors: Liyun Zhao, Paul D. Beer, Kathleen M Mullen, Michal J Chmielewski, Asha Brown, Nick Bampos, Jason J DavisAbstract:The surface covalent attachment of fluorescent axles of Indolocarbazole enables anion templation to be exploited in the formation of pseudorotaxane assembliesvia the threading of neutral isophthalamide macrocycles. In utilising the surface of polystyrene beads this threading process can be followed by both magnetic resonance methods and changes in the axle fluorescent emission spectrum. The analogous surface assembly and anion templated threading can be achieved, with fluoride and sulfate, on silica nanoparticles where anion recognition and macrocycle threading are associated with equivalent and specific optical change.
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anion templated formation of pseudorotaxane and rotaxane monolayers on gold from neutral components
Langmuir, 2009Co-Authors: Liyun Zhao, Kathleen M Mullen, Michal J Chmielewski, Asha Brown, Jason J Davis, Robert M J Jacobs, Paul D. BeerAbstract:The surface covalent attachment of Indolocarbazole axles enables anion templation to be exploited in the formation of pseudorotaxane assemblies via the threading of neutral isophthalamide macrocycles from solution. The anion selectivity of this templating process can be monitored by a number of surface spectroscopic methods and shows subtle differences compared to the same process in solution. Though the fluxional and disordered nature of ethylene glycol extended axle adlayers prohibits detectable threading on the surface, rotaxane monolayers can be generated by a preassociation of the components and templating anion in solution. The threaded macrocycles therein can subsequently be released and detected by mass spectrometry by reductive stripping of the axle.
Cheol Hong Cheon - One of the best experts on this subject based on the ideXlab platform.
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total syntheses of arcyriaflavin a and calothrixin b using 2 2 bisindole 3 acetic acid derivative as a common intermediate
Organic Letters, 2017Co-Authors: Sungjong Lee, Kyung-hee Kim, Cheol Hong CheonAbstract:A new protocol for the synthesis of 2,2′-bisindole-3-acetic acid derivatives from aldimines derived from 2-aminocinnamic acid derivatives and indole-2-carboxaldehyde was developed via a cyanide-catalyzed imino-Stetter reaction. With this protocol, the divergent total syntheses of arcyriaflavin A, a representative Indolocarbazole natural product, and calothrixin B, a representative indolo[3,2-j]phenanthridine natural product, were completed using a 2,2′-bisindole-3-acetic acid derivative as the common intermediate.
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Total Syntheses of Arcyriaflavin A and Calothrixin B Using 2,2′-Bisindole-3-acetic Acid Derivative as a Common Intermediate
2017Co-Authors: Sungjong Lee, Kyung-hee Kim, Cheol Hong CheonAbstract:A new protocol for the synthesis of 2,2′-bisindole-3-acetic acid derivatives from aldimines derived from 2-aminocinnamic acid derivatives and indole-2-carboxaldehyde was developed via a cyanide-catalyzed imino-Stetter reaction. With this protocol, the divergent total syntheses of arcyriaflavin A, a representative Indolocarbazole natural product, and calothrixin B, a representative indolo[3,2-j]phenanthridine natural product, were completed using a 2,2′-bisindole-3-acetic acid derivative as the common intermediate
Asha Brown - One of the best experts on this subject based on the ideXlab platform.
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active metal template synthesis of a neutral Indolocarbazole containing 2 rotaxane host system for selective oxoanion recognition
Organic and Biomolecular Chemistry, 2017Co-Authors: Asha Brown, Kathleen M Mullen, Thomas Lang, Paul D. BeerAbstract:An active metal template strategy was used to synthesise a neutral Indolocarbazole containing [2]rotaxane anion host system. 1H NMR anion binding investigations reveal that the [2]rotaxane recognises a range of monoanions in acetone-d5 : D2O 95 : 5 with an unusual interlocked host selectivity for acetate and dihydrogenphosphate oxoanions over halides. The rotaxane displays an overall selectivity for the sulfate dianion, favouring a 2 : 1 host : guest binding stoichiometry at low sulfate concentration and a 1 : 1 stoichiometry in the presence of excess sulfate. Fluorescence titration demonstrates that the [2]rotaxane is also capable of sensing guest anions via significant changes in its emission spectrum.
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anion templated assembly of an Indolocarbazole containing pseudorotaxane on beads and silica nanoparticles
New Journal of Chemistry, 2009Co-Authors: Liyun Zhao, Paul D. Beer, Kathleen M Mullen, Michal J Chmielewski, Asha Brown, Nick Bampos, Jason J DavisAbstract:The surface covalent attachment of fluorescent axles of Indolocarbazole enables anion templation to be exploited in the formation of pseudorotaxane assembliesvia the threading of neutral isophthalamide macrocycles. In utilising the surface of polystyrene beads this threading process can be followed by both magnetic resonance methods and changes in the axle fluorescent emission spectrum. The analogous surface assembly and anion templated threading can be achieved, with fluoride and sulfate, on silica nanoparticles where anion recognition and macrocycle threading are associated with equivalent and specific optical change.
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anion templated formation of pseudorotaxane and rotaxane monolayers on gold from neutral components
Langmuir, 2009Co-Authors: Liyun Zhao, Kathleen M Mullen, Michal J Chmielewski, Asha Brown, Jason J Davis, Robert M J Jacobs, Paul D. BeerAbstract:The surface covalent attachment of Indolocarbazole axles enables anion templation to be exploited in the formation of pseudorotaxane assemblies via the threading of neutral isophthalamide macrocycles from solution. The anion selectivity of this templating process can be monitored by a number of surface spectroscopic methods and shows subtle differences compared to the same process in solution. Though the fluxional and disordered nature of ethylene glycol extended axle adlayers prohibits detectable threading on the surface, rotaxane monolayers can be generated by a preassociation of the components and templating anion in solution. The threaded macrocycles therein can subsequently be released and detected by mass spectrometry by reductive stripping of the axle.
Kathleen M Mullen - One of the best experts on this subject based on the ideXlab platform.
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active metal template synthesis of a neutral Indolocarbazole containing 2 rotaxane host system for selective oxoanion recognition
Organic and Biomolecular Chemistry, 2017Co-Authors: Asha Brown, Kathleen M Mullen, Thomas Lang, Paul D. BeerAbstract:An active metal template strategy was used to synthesise a neutral Indolocarbazole containing [2]rotaxane anion host system. 1H NMR anion binding investigations reveal that the [2]rotaxane recognises a range of monoanions in acetone-d5 : D2O 95 : 5 with an unusual interlocked host selectivity for acetate and dihydrogenphosphate oxoanions over halides. The rotaxane displays an overall selectivity for the sulfate dianion, favouring a 2 : 1 host : guest binding stoichiometry at low sulfate concentration and a 1 : 1 stoichiometry in the presence of excess sulfate. Fluorescence titration demonstrates that the [2]rotaxane is also capable of sensing guest anions via significant changes in its emission spectrum.
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anion templated assembly of an Indolocarbazole containing pseudorotaxane on beads and silica nanoparticles
New Journal of Chemistry, 2009Co-Authors: Liyun Zhao, Paul D. Beer, Kathleen M Mullen, Michal J Chmielewski, Asha Brown, Nick Bampos, Jason J DavisAbstract:The surface covalent attachment of fluorescent axles of Indolocarbazole enables anion templation to be exploited in the formation of pseudorotaxane assembliesvia the threading of neutral isophthalamide macrocycles. In utilising the surface of polystyrene beads this threading process can be followed by both magnetic resonance methods and changes in the axle fluorescent emission spectrum. The analogous surface assembly and anion templated threading can be achieved, with fluoride and sulfate, on silica nanoparticles where anion recognition and macrocycle threading are associated with equivalent and specific optical change.
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anion templated formation of pseudorotaxane and rotaxane monolayers on gold from neutral components
Langmuir, 2009Co-Authors: Liyun Zhao, Kathleen M Mullen, Michal J Chmielewski, Asha Brown, Jason J Davis, Robert M J Jacobs, Paul D. BeerAbstract:The surface covalent attachment of Indolocarbazole axles enables anion templation to be exploited in the formation of pseudorotaxane assemblies via the threading of neutral isophthalamide macrocycles from solution. The anion selectivity of this templating process can be monitored by a number of surface spectroscopic methods and shows subtle differences compared to the same process in solution. Though the fluxional and disordered nature of ethylene glycol extended axle adlayers prohibits detectable threading on the surface, rotaxane monolayers can be generated by a preassociation of the components and templating anion in solution. The threaded macrocycles therein can subsequently be released and detected by mass spectrometry by reductive stripping of the axle.
Jon S Thorson - One of the best experts on this subject based on the ideXlab platform.
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cytotoxic Indolocarbazoles from actinomadura melliaura atcc 39691
Journal of Natural Products, 2015Co-Authors: Khaled A Shaaban, Sherif I Elshahawi, Xiachang Wang, Jamie Horn, Madan K Kharel, Markos Leggas, Jon S ThorsonAbstract:Actinomadura melliaura ATCC 39691, a strain isolated from a soil sample collected in Bristol Cove, California, is a known producer of the disaccharide-substituted AT2433 Indolocarbazoles (6–9). Reinvestigation of this strain using new media conditions led to >40-fold improvement in the production of previously reported AT2433 metabolites and the isolation and structure elucidation of the four new analogues, AT2433-A3, A4, A5, and B3 (1–4). The availability of this broader set of compounds enabled a subsequent small antibacterial/fungal/cancer SAR study that revealed disaccharyl substitution, N-6 methylation, and C-11 chlorination as key modulators of bioactivity. The slightly improved anticancer potency of the newly reported N-6-desmethyl 1 (compared to 6) contrasts extensive SAR of monoglycosylated rebeccamycin-type topoisomerase I inhibitors where N-6 alkylation has contributed to improved potency and ADME. Complete 2D NMR assignments for the known metabolite BMY-41219 (5) and 13C NMR spectroscopic data...
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Cytotoxic Indolocarbazoles from Actinomadura melliaura ATCC 39691
2015Co-Authors: Khaled A. Shaaban, Sherif I Elshahawi, Xiachang Wang, Jamie Horn, Markos Leggas, Madan K. Kharel, Jon S ThorsonAbstract:Actinomadura melliaura ATCC 39691, a strain isolated from a soil sample collected in Bristol Cove, California, is a known producer of the disaccharide-substituted AT2433 Indolocarbazoles (6–9). Reinvestigation of this strain using new media conditions led to >40-fold improvement in the production of previously reported AT2433 metabolites and the isolation and structure elucidation of the four new analogues, AT2433-A3, A4, A5, and B3 (1–4). The availability of this broader set of compounds enabled a subsequent small antibacterial/fungal/cancer SAR study that revealed disaccharyl substitution, N-6 methylation, and C-11 chlorination as key modulators of bioactivity. The slightly improved anticancer potency of the newly reported N-6-desmethyl 1 (compared to 6) contrasts extensive SAR of monoglycosylated rebeccamycin-type topoisomerase I inhibitors where N-6 alkylation has contributed to improved potency and ADME. Complete 2D NMR assignments for the known metabolite BMY-41219 (5) and 13C NMR spectroscopic data for the known analogue AT2433-B1 (7) are also provided for the first time
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Deciphering Indolocarbazole and enediyne aminodideoxypentose biosynthesis through comparative genomics: insights from the AT2433 biosynthetic locus.
Chemistry & biology, 2006Co-Authors: Qunjie Gao, Changsheng Zhang, Sophie Blanchard, Jon S ThorsonAbstract:AT2433, an Indolocarbazole antitumor antibiotic, is structurally distinguished by its aminodideoxypentose-containing disaccharide and asymmetrically halogenated N-methylated aglycon. Cloning and sequence analysis of AT2433 gene cluster and comparison of this locus with that encoding for rebeccamycin and the gene cluster encoding calicheamicin present an opportunity to study the aminodideoxypentose biosynthesis via comparative genomics. The locus was confirmed via in vitro biochemical characterization of two methyltransferases--one common to AT2433 and rebeccamycin, the other unique to AT2433--as well as via heterologous expression and in vivo bioconversion experiments using the AT2433 N-glycosyltransferase. Preliminary studies of substrate tolerance for these three enzymes reveal the potential to expand upon the enzymatic diversification of Indolocarbazoles. Moreover, this work sets the stage for future studies regarding the origins of the Indolocarbazole maleimide nitrogen and Indolocarbazole asymmetry.