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Mark V Lawson - One of the best experts on this subject based on the ideXlab platform.
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non commutative stone duality inverse semigroups topological groupoids and c algebras
International Journal of Algebra and Computation, 2012Co-Authors: Mark V LawsonAbstract:We study a non-commutative generalization of Stone duality that connects a class of inverse semigroups, called Boolean inverse ∧-semigroups, with a class of topological groupoids, called Hausdorff Boolean groupoids. Much of the paper is given over to showing that Boolean inverse ∧-semigroups arise as completions of inverse ∧-semigroups we call pre-Boolean. An inverse ∧-semigroup is pre-Boolean if and only if every tight filter is an ultrafilter, where tight filters are defined by combining ideas of both Exel and Lenz. A simple necessary condition for a semigroup to be pre-Boolean is derived and a variety of examples of inverse semigroups are shown to satisfy it. Thus the Polycyclic inverse monoids, and certain Rees matrix semigroups over the Polycyclics, are pre-Boolean and it is proved that the groups of units of their completions are precisely the Thompson–Higman groups Gn, r. The inverse semigroups arising from suitable directed graphs are also pre-Boolean and the topological groupoids arising from these graph inverse semigroups under our non-commutative Stone duality are the groupoids that arise from the Cuntz–Krieger C*-algebras. An elementary application of our theory shows that the finite, fundamental Boolean inverse ∧-semigroups are just the finite direct products of finite symmetric inverse monoids. Finally, we explain how tight filters are related to prime filters setting the scene for future work.
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non commutative stone duality inverse semigroups topological groupoids and c algebras
arXiv: Category Theory, 2011Co-Authors: Mark V LawsonAbstract:We study a non-commutative generalization of Stone duality that connects a class of inverse semigroups, called Boolean inverse $\wedge$-semigroups, with a class of topological groupoids, called Hausdorff Boolean groupoids. Much of the paper is given over to showing that Boolean inverse $\wedge$-semigroups arise as completions of inverse semigroups we call pre-Boolean. An inverse $\wedge$-semigroup is pre-Boolean if and only if every tight filter is an ultrafilter, where the definition of a tight filter is obtained by combining work of both Exel and Lenz. A simple necessary condition for a semigroup to be pre-Boolean is derived and a variety of examples of inverse semigroups are shown to satisfy it. Thus the Polycyclic inverse monoids, and certain Rees matrix semigroups over the Polycyclics, are pre-Boolean and it is proved that the groups of units of their completions are precisely the Thompson-Higman groups $G_{n,r}$. The inverse semigroups arising from suitable directed graphs are also pre-Boolean and the topological groupoids arising from these graph inverse semigroups under our non-commutative Stone duality are the groupoids that arise from the Cuntz-Krieger $C^{\ast}$-algebras.
Haruhiko Fuwa - One of the best experts on this subject based on the ideXlab platform.
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design and synthesis of skeletal analogues of gambierol attenuation of amyloid β and tau pathology with voltage gated potassium channel and n methyl d aspartate receptor implications
Journal of the American Chemical Society, 2012Co-Authors: Eva Alonso, Haruhiko Fuwa, Makoto Sasaki, Carmen Vale, Yuto Suga, Tomomi Goto, Yu Konno, Frank M Laferla, Mercedes R Vieytes, Lydia GimenezllortAbstract:Gambierol is a potent neurotoxin that belongs to the family of marine Polycyclic ether natural products and primarily targets voltage-gated potassium channels (Kv channels) in excitable membranes. Previous work in the chemistry of marine Polycyclic ethers has suggested the critical importance of the full length of Polycyclic ether skeleton for potent biological activity. Although we have previously investigated structure–activity relationships (SARs) of the peripheral functionalities of gambierol, it remained unclear whether the whole Polycyclic ether skeleton is needed for its cellular activity. In this work, we designed and synthesized two truncated skeletal analogues of gambierol comprising the EFGH- and BCDEFGH-rings of the parent compound, both of which surprisingly showed similar potency to gambierol on voltage-gated potassium channels (Kv) inhibition. Moreover, we examined the effect of these compounds in an in vitro model of Alzheimer’s disease (AD) obtained from triple transgenic (3xTg-AD) mice, ...
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recent applications of the suzuki miyaura cross coupling to complex Polycyclic ether synthesis
ChemInform, 2012Co-Authors: Haruhiko Fuwa, Makoto Ebine, Makoto SasakiAbstract:The ladder-shaped Polycyclic ether marine natural products present formidable and challenging synthetic targets due to their structural complexity, and exceptionally potent biological activities. Over the past decade, however, the limited availability of these substances from natural sources has precluded detailed biological studies. There has been an urgent need for means to supply useful quantities of these natural products and their analogues by total synthesis. We have developed a highly convergent strategy for the rapid and efficient assembly of Polycyclic ether arrays, which relies on the palladium-catalyzed Suzuki-Miyaura cross-coupling reaction of cyclic enol triflates or phosphates. The utility of this strategy has been demonstrated by its application to the convergent total synthesis of the Polycyclic ether class of natural products.
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Convergent strategies for the total synthesis of Polycyclic ether marine metabolites.
Natural product reports, 2008Co-Authors: Makoto Sasaki, Haruhiko FuwaAbstract:Marine Polycyclic ether natural products continue to fascinate chemists and biologists due to their exceptionally large and complex molecular architectures and potent and diverse biological activities. Tremendous progress has been made over the past decade toward the total synthesis of marine Polycyclic ether natural products. In this area, a convergent strategy for assembling small fragments into an entire molecule always plays a key role in successful total synthesis. This review describes our efforts to develop convergent strategies for the synthesis of Polycyclic ethers and their application to the total synthesis of gambierol, gymnocin-A, and brevenal, and to the partial synthesis of the central part of ciguatoxins and the nonacyclic polyether skeleton of gambieric acids.
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recent advances in the synthesis of marine Polycyclic ether natural products
Current Opinion in Drug Discovery & Development, 2007Co-Authors: Haruhiko Fuwa, Makoto SasakiAbstract:For more than twenty years, chemists and biologists have been fascinated by the highly complex molecular architectures and the diverse and potent biological activities of marine Polycyclic ether natural products. Given the scarce availability of these intriguing substances from natural sources, total chemical synthesis is the only way to obtain sufficient quantities for biological investigation. This review describes recent synthetic advances in the field of marine Polycyclic ether natural products and their successful implementation in total synthesis endeavors.
Makoto Sasaki - One of the best experts on this subject based on the ideXlab platform.
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design and synthesis of skeletal analogues of gambierol attenuation of amyloid β and tau pathology with voltage gated potassium channel and n methyl d aspartate receptor implications
Journal of the American Chemical Society, 2012Co-Authors: Eva Alonso, Haruhiko Fuwa, Makoto Sasaki, Carmen Vale, Yuto Suga, Tomomi Goto, Yu Konno, Frank M Laferla, Mercedes R Vieytes, Lydia GimenezllortAbstract:Gambierol is a potent neurotoxin that belongs to the family of marine Polycyclic ether natural products and primarily targets voltage-gated potassium channels (Kv channels) in excitable membranes. Previous work in the chemistry of marine Polycyclic ethers has suggested the critical importance of the full length of Polycyclic ether skeleton for potent biological activity. Although we have previously investigated structure–activity relationships (SARs) of the peripheral functionalities of gambierol, it remained unclear whether the whole Polycyclic ether skeleton is needed for its cellular activity. In this work, we designed and synthesized two truncated skeletal analogues of gambierol comprising the EFGH- and BCDEFGH-rings of the parent compound, both of which surprisingly showed similar potency to gambierol on voltage-gated potassium channels (Kv) inhibition. Moreover, we examined the effect of these compounds in an in vitro model of Alzheimer’s disease (AD) obtained from triple transgenic (3xTg-AD) mice, ...
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recent applications of the suzuki miyaura cross coupling to complex Polycyclic ether synthesis
ChemInform, 2012Co-Authors: Haruhiko Fuwa, Makoto Ebine, Makoto SasakiAbstract:The ladder-shaped Polycyclic ether marine natural products present formidable and challenging synthetic targets due to their structural complexity, and exceptionally potent biological activities. Over the past decade, however, the limited availability of these substances from natural sources has precluded detailed biological studies. There has been an urgent need for means to supply useful quantities of these natural products and their analogues by total synthesis. We have developed a highly convergent strategy for the rapid and efficient assembly of Polycyclic ether arrays, which relies on the palladium-catalyzed Suzuki-Miyaura cross-coupling reaction of cyclic enol triflates or phosphates. The utility of this strategy has been demonstrated by its application to the convergent total synthesis of the Polycyclic ether class of natural products.
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Convergent strategies for the total synthesis of Polycyclic ether marine metabolites.
Natural product reports, 2008Co-Authors: Makoto Sasaki, Haruhiko FuwaAbstract:Marine Polycyclic ether natural products continue to fascinate chemists and biologists due to their exceptionally large and complex molecular architectures and potent and diverse biological activities. Tremendous progress has been made over the past decade toward the total synthesis of marine Polycyclic ether natural products. In this area, a convergent strategy for assembling small fragments into an entire molecule always plays a key role in successful total synthesis. This review describes our efforts to develop convergent strategies for the synthesis of Polycyclic ethers and their application to the total synthesis of gambierol, gymnocin-A, and brevenal, and to the partial synthesis of the central part of ciguatoxins and the nonacyclic polyether skeleton of gambieric acids.
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recent advances in the synthesis of marine Polycyclic ether natural products
Current Opinion in Drug Discovery & Development, 2007Co-Authors: Haruhiko Fuwa, Makoto SasakiAbstract:For more than twenty years, chemists and biologists have been fascinated by the highly complex molecular architectures and the diverse and potent biological activities of marine Polycyclic ether natural products. Given the scarce availability of these intriguing substances from natural sources, total chemical synthesis is the only way to obtain sufficient quantities for biological investigation. This review describes recent synthetic advances in the field of marine Polycyclic ether natural products and their successful implementation in total synthesis endeavors.
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total synthesis and structure activity relationship of a cytotoxic Polycyclic ether gymnocin a
Journal of Synthetic Organic Chemistry Japan, 2006Co-Authors: Chihiro Tsukano, Makoto SasakiAbstract:Gymnocin-A is a Polycyclic ether toxin, isolated from the notorious red tide dinoflagellate, Karenia mikimotoi. Structurally, it is characterized by 14 contiguous and saturated ether rings and a 2-methyl-2-butenal side chain. The toxin is a rare Polycyclic ether natural product that exhibits cytotoxicity against P 388 murine leukemia (IC50=1.3 μg/mL); however, the biological mechanism of action remains unknown to date. We have accomplished a highly convergent and efficient total synthesis of gymnocin-A by using our developed B-alkyl Suzuki-Miyaura coupling-based methodology. The convergent nature of our synthesis is well suited for preparation of various structural analogues of gymnocin-A to explore the structure-activity relationship (SAR). The results of SAR studies indicated that an α, β-unsaturated aldehyde functionality of the side chain and the molecular length of the Polycyclic ether skeleton were the crucial structural elements required for cytotoxicity.
James S Chickos - One of the best experts on this subject based on the ideXlab platform.
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vapor pressure and vaporization enthalpy studies of longifolene isolongifolene and β myrcene by correlation gas chromatography
The Journal of Chemical Thermodynamics, 2019Co-Authors: Patamaporn Umnahanant, Ameera Zafar, Vinay Kankala, James S ChickosAbstract:Abstract This paper examines the use of two different sets of standards, n-alkanes and a more structurally diverse group of cyclic and Polycyclic molecules to evaluate the vaporization enthalpies and vapor pressures of (+) longifolene(−)-isolongifolene and β-myrcene using correlation gas chromatography. Both sets of standards provide similar vaporization enthalpies and vapor pressures of the title compounds at T = 298.15 K within their experimental uncertainties. The group of cyclic and Polycyclic hydrocarbons reproduce the vapor pressures of the sesquiterpene hydrocarbons at elevated temperatures best while the same properties of β-myrcene are best reproduced by the n-alkanes as judged by reproduction of both experimental boiling temperatures measured at reduced pressures and vapor pressures. The results confirm previous findings obtained on Polycyclic hydrocarbons regarding the suitability of using structurally similar standards and suggest that n-alkanes are suitable vapor pressure standards for highly unsaturated acyclic hydrocarbons.
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the vaporization enthalpy and vapor pressures of liquid adamantane diamantane and α and β cedrene by correlation gas chromatography
The Journal of Chemical Thermodynamics, 2018Co-Authors: Carissa Nelson, James S ChickosAbstract:Abstract This work examines the use of two different sets of standards to evaluate vaporization enthalpies and liquid vapor pressures of a series of Polycyclic hydrocarbons that include adamantane, diamantane, and α and β-cedrene by correlation gas chromatography. Several n-alkanes and a series of cyclic and Polycyclic hydrocarbons were selected as standards to independently evaluate the appropriateness of using n-alkanes to evaluate these properties in two branched Polycyclic sesquiterpenes. Vapor pressures of two of the Polycyclic hydrocarbons examined, 1,3-dimethyladamantane and 1,4-di-t-butylbenzene, are known and the results obtained using n-alkanes as standards were used for comparisons. Standards for evaluation of adamantane and diamantane included these two compounds along with α-pinene, and camphene; a series of n-alkanes were also used in separate experiments for evaluation of the adamantanoids. The n-alkane standards included decane and dodecane through to pentadecane. Vapor pressures for adamantane and diamantane evaluated in this work were combined with literature values for 1,3-dimethyladamantane and 1,4-di-t-butylbenzene at elevated temperatures to also evaluate liquid vapor pressures and vaporization enthalpies for α- and β-cedrene. The results were compared to those evaluated independently using n-alkanes. The results of the experiments are discussed.
Cornelis J Van Der Schyf - One of the best experts on this subject based on the ideXlab platform.
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pharmacology and structure activity relationships of bioactive Polycyclic cage compounds a focus on pentacycloundecane derivatives
Medicinal Research Reviews, 2005Co-Authors: Werne J Geldenhuys, Sarel F Mala, Jeffrey R Loomquis, A P Marchand, Cornelis J Van Der SchyfAbstract:The chemistry of organic Polycyclic cage compounds has intrigued medicinal chemists for over 50 years, yet little is published about their pharmacological profiles. Polycyclic cage compounds have important pharmaceutical applications, ranging from the symptomatic and proposed curative treatment of neurodegenerative diseases such as Parkinson's and Alzheimer's disease (e.g., amantadine and memantine), to use as anti-viral agents against influenza and the immunodeficiency virus (HIV). The Polycyclic cage appears to be a useful scaffold to yield drugs with a wide scope of applications, and can be used also to modify and improve the pharmacokinetic and pharmacodynamic properties of drugs in current use. This review attempts to summarize the pharmacological profiles of Polycyclic cage compounds with an emphasis on the lesser known pentacycloundecanes, homocubanes, and trishomocubanes.
