The Experts below are selected from a list of 216 Experts worldwide ranked by ideXlab platform
Janusz Rachon - One of the best experts on this subject based on the ideXlab platform.
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Unexpected Thioketene Derivative Formation During Thioacyl Dithiophosphate Synthesis
Synthetic Communications, 2003Co-Authors: Leszek Doszczak, Jan F. Biernat, Victor Ch. Kravtsov, Janusz RachonAbstract:The scope and limitations of the Thioacylation method using thioacyl dithiophosphates were investigated. Thioacyl dithiophosphates are formed in the reaction of acyl dithiophosphates with dithiophosphoric acid. However when the acyl moiety contains two α-substituents then a thioketene derivative is formed thus lowering the yield of expected thioacyl dithiophosphate.
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synthesis of s thioacyl dithiophosphates efficient and chemoselective thioacylating agents
Journal of The Chemical Society-perkin Transactions 1, 2002Co-Authors: Leszek Doszczak, Janusz RachonAbstract:Easily available acyl dithiophosphates are not stable and isomerise reversibly to O-thioacyl monothiophosphates, especially when subjected to heating. Much slower but probably irreversible isomerisation to S-thioacyl monothiophosphates occurs. Since equilibrium states are established and S-thioacyl (mono)thiophosphates form slowly, reaction mixtures contain generally both thioacylating and acylating agents, and consequently cannot be used for efficient Thioacylation. On the other hand, treatment of a mixture of isomeric anhydrides with an excess of a dithiophosphoric acid leads to exclusive formation of S-thioacyl dithiophosphates. They appear to be excellent thioacylating agents: relatively stable, inert towards water and oxygen and therefore easy to handle. Reactions with nitrogen or sulfur nucleophiles proceed very rapidly under ambient conditions, yielding respective thioacyl derivatives. Isolation of the products is very simple. Due to the low reactivity of S-thioacyl dithiophosphates towards oxygen nucleophiles they can be used for direct Thioacylation of multifunctional nucleophiles with unprotected hydroxy groups. Respective thioacyl derivatives cannot readily be obtained using other methods.
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New, efficient and chemoselective method of Thioacylation, starting from carboxylic acids
Chemical Communications, 2000Co-Authors: Leszek Doszczak, Janusz RachonAbstract:S-Acylation of dithiophosphoric acids yields mixed anhydrides 3; they readily isomerize to O-thioacyl 4 and S-thioacyl monothiophosphates 5, which treated with the excess of dithiophosphoric acid 2 can be easily converted into thioacyl dithiophosphates 6, excellent thioacylating reagents.
Alfred G Gilman - One of the best experts on this subject based on the ideXlab platform.
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characterization of saccharomyces cerevisiae acyl protein thioesterase 1 the enzyme responsible for g protein α subunit deacylation in vivo
Journal of Biological Chemistry, 2002Co-Authors: Joseph A Duncan, Alfred G GilmanAbstract:Abstract Thioacylation is a reversible lipid modification of proteins that plays a role in the regulation of signal transduction. Acyl-protein thioesterase 1 (APT1) was identified as an enzyme capable of deacylating some thioacylated proteins in vitro. Saccharomyces cerevisiae open reading frame YLR118c encodes an enzyme homologous to Rattus norvegicus APT1. We demonstrate that the catalytic activity of the protein encoded by the yeast open reading frame is similar to that of rat APT1, and we designate the protein S. cerevisiae Apt1p. Yeasts bearing a disruption of the APT1 gene lack significant biochemically detectable acyl-protein thioesterase activity. They also fail to deacylate Gpa1p, the yeast Gα subunit, in metabolic radiolabeling studies. We conclude that native APT1 is the enzyme responsible for Gα subunit deacylation in S. cerevisiae and presumably other eukaryotes as well.
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a cytoplasmic acyl protein thioesterase that removes palmitate from g protein α subunits and p21 ras
Journal of Biological Chemistry, 1998Co-Authors: Joseph A Duncan, Alfred G GilmanAbstract:Abstract Thioacylation is one of a handful of reversible covalent protein modifications, but the enzymes responsible for addition and removal of long chain fatty acids from protein cysteine residues in vivo have not yet been identified. The α subunits of some heterotrimeric G proteins cycle between thioacylated and deacylated states in a receptor-regulated fashion. We have identified, purified, and characterized an enzyme acyl-protein thioesterase that deacylates Gα proteins and at least some other thioacyl protein substrates, including Ha-RAS. The action of this enzyme on thioacylated heterotrimeric Gs is regulated by activation of the G protein. Although native and recombinant acyl-protein thioesterases act as both acyl-protein thioesterases and lysophospholipases in vitro, we demonstrate by transfection that the enzyme can accelerate the turnover of thioacyl groups on Gsα in vivo.
Gerald Pattenden - One of the best experts on this subject based on the ideXlab platform.
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Total synthesis of (+)-curacin A, a novel antimitotic metabolite from a cyanobacterium
Journal of the Chemical Society Perkin Transactions 1, 2002Co-Authors: James C Muir, Gerald PattendenAbstract:A concise total synthesis of (+)-curacin A, a potent antimitotic agent isolated from the cyanobacterium Lyngbya majuscula, is described. The synthesis features a new strategy to the 2-cyclopropyl-4-alkenyl substituted thiazoline unit in the natural product involving facile and selective Thioacylation of the amino-alcohol 10 with the benzotriazole derived thioamide 11, leading to 28, as a key step. Cyclodehydration of 28 using Burgess' reagent then completed the synthesis of curacin A 1.
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a concise total synthesis of curacin a a novel cyclopropyl substituted thiazoline from the cyanobacterium lyngbya majuscula
Tetrahedron Letters, 1998Co-Authors: James C Muir, Gerald PattendenAbstract:A total synthesis of (+)-curacin A 1 which features a facile and selective Thioacylation of the polyene amino-alcohol 2 with the benzotriazole-derived cyclopropyl thioamide 3, leading to 15, as a key step is described.
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A CONCISE TOTAL SYNTHESIS OF (+)-CURACIN A, A NOVEL CYCLOPROPYL-SUBSTITUTED THIAZOLINE FROM THE CYANOBACTERIUM LYNGBYA, MAJUSCULA
Tetrahedron Letters, 1998Co-Authors: James C Muir, Gerald PattendenAbstract:A total synthesis of (+)-curacin A 1 which features a facile and selective Thioacylation of the polyene amino-alcohol 2 with the benzotriazole-derived cyclopropyl thioamide 3, leading to 15, as a key step is described.
Sylvain Antoniotti - One of the best experts on this subject based on the ideXlab platform.
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Novel Radical Tandem 1,6‐Enynes Thioacylation/Cyclization: Au—Pd Nanoparticles Catalysis versus Thermal Activation as a Function of the Substrate Specificity.
ChemInform, 2015Co-Authors: Irene Notar Francesco, Justine Giauffret, Fabien Fontaine-vive, Jennifer K. Edwards, Christopher J. Kiely, Graham J. Hutchings, Sylvain AntoniottiAbstract:The Thioacylation/cyclization in the presence of the nanosized catalyst alloy proceeds under mild conditions.
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novel radical tandem 1 6 enynes Thioacylation cyclization au pd nanoparticles catalysis versus thermal activation as a function of the substrate specificity
ChemInform, 2015Co-Authors: Irene Notar Francesco, Justine Giauffret, Jennifer K. Edwards, Christopher J. Kiely, Graham J. Hutchings, Fabien Fontainevive, Sylvain AntoniottiAbstract:The Thioacylation/cyclization in the presence of the nanosized catalyst alloy proceeds under mild conditions.
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novel radical tandem 1 6 enynes Thioacylation cyclization au pd nanoparticles catalysis versus thermal activation as a function of the substrate specificity
Tetrahedron, 2014Co-Authors: Irene Notar Francesco, Justine Giauffret, Jennifer K. Edwards, Christopher J. Kiely, Graham J. Hutchings, Fabien Fontainevive, Sylvain AntoniottiAbstract:Abstract We studied the reactivity of 1,6-enynes with thioacetic acid (AcSH) under either thermal conditions or in the presence of catalytic amounts of supported Au or Au–Pd nanoparticles (NPs) under mild conditions. The 1,6-enynes undergo a tandem Thioacylation/cyclization to original cyclic products featuring either a homoallylic thioester function or an enol thioester function depending on the substrate topology. Interestingly, the former process was found more efficient when performed in the presence of Au–Pd NPs while the latter process can be efficiently carried out under thermal conditions (100 °C). The reaction proceeds by a radical mechanism and the presence of precious metal NPs seems to stabilize the formation of free radical intermediates, as supported by experimental and theoretical results.
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Novel radical tandem 1,6-enynes Thioacylation/cyclization: Au–Pd nanoparticles catalysis versus thermal activation as a function of the substrate specificity
Tetrahedron, 2014Co-Authors: Irene Notar Francesco, Justine Giauffret, Fabien Fontaine-vive, Jennifer K. Edwards, Christopher J. Kiely, Graham J. Hutchings, Sylvain AntoniottiAbstract:Abstract We studied the reactivity of 1,6-enynes with thioacetic acid (AcSH) under either thermal conditions or in the presence of catalytic amounts of supported Au or Au–Pd nanoparticles (NPs) under mild conditions. The 1,6-enynes undergo a tandem Thioacylation/cyclization to original cyclic products featuring either a homoallylic thioester function or an enol thioester function depending on the substrate topology. Interestingly, the former process was found more efficient when performed in the presence of Au–Pd NPs while the latter process can be efficiently carried out under thermal conditions (100 °C). The reaction proceeds by a radical mechanism and the presence of precious metal NPs seems to stabilize the formation of free radical intermediates, as supported by experimental and theoretical results.
Leszek Doszczak - One of the best experts on this subject based on the ideXlab platform.
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Unexpected Thioketene Derivative Formation During Thioacyl Dithiophosphate Synthesis
Synthetic Communications, 2003Co-Authors: Leszek Doszczak, Jan F. Biernat, Victor Ch. Kravtsov, Janusz RachonAbstract:The scope and limitations of the Thioacylation method using thioacyl dithiophosphates were investigated. Thioacyl dithiophosphates are formed in the reaction of acyl dithiophosphates with dithiophosphoric acid. However when the acyl moiety contains two α-substituents then a thioketene derivative is formed thus lowering the yield of expected thioacyl dithiophosphate.
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synthesis of s thioacyl dithiophosphates efficient and chemoselective thioacylating agents
Journal of The Chemical Society-perkin Transactions 1, 2002Co-Authors: Leszek Doszczak, Janusz RachonAbstract:Easily available acyl dithiophosphates are not stable and isomerise reversibly to O-thioacyl monothiophosphates, especially when subjected to heating. Much slower but probably irreversible isomerisation to S-thioacyl monothiophosphates occurs. Since equilibrium states are established and S-thioacyl (mono)thiophosphates form slowly, reaction mixtures contain generally both thioacylating and acylating agents, and consequently cannot be used for efficient Thioacylation. On the other hand, treatment of a mixture of isomeric anhydrides with an excess of a dithiophosphoric acid leads to exclusive formation of S-thioacyl dithiophosphates. They appear to be excellent thioacylating agents: relatively stable, inert towards water and oxygen and therefore easy to handle. Reactions with nitrogen or sulfur nucleophiles proceed very rapidly under ambient conditions, yielding respective thioacyl derivatives. Isolation of the products is very simple. Due to the low reactivity of S-thioacyl dithiophosphates towards oxygen nucleophiles they can be used for direct Thioacylation of multifunctional nucleophiles with unprotected hydroxy groups. Respective thioacyl derivatives cannot readily be obtained using other methods.
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New, efficient and chemoselective method of Thioacylation, starting from carboxylic acids
Chemical Communications, 2000Co-Authors: Leszek Doszczak, Janusz RachonAbstract:S-Acylation of dithiophosphoric acids yields mixed anhydrides 3; they readily isomerize to O-thioacyl 4 and S-thioacyl monothiophosphates 5, which treated with the excess of dithiophosphoric acid 2 can be easily converted into thioacyl dithiophosphates 6, excellent thioacylating reagents.