The Experts below are selected from a list of 348 Experts worldwide ranked by ideXlab platform
David Crich - One of the best experts on this subject based on the ideXlab platform.
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direct chemical synthesis of β mannopyranosides and other glycosides via glycosyl triflates
ChemInform, 2010Co-Authors: David Crich, Sanxing SunAbstract:Abstract High yield, highly stereoselective methods for the synthesis of β-mannopyranosides of primary, secondary, and tertiary alcohols are presented. Activation of mannosyl sulfoxides or mannosyl thioglycosides with Trifluoromethanesulfonic Anhydride or benzenesulfenyl triflate, respectively, leads to the efficient formation of α-mannosyl triflates at −78 °C in dichloromethane, in the presence of 2,6-di- tert -butyl-4-methylpyridine. These triflates then react S N 2-like with alcohols to give the β-mannosides. The use of a 4,6- O -benzylidene protected mannose is required for high selectivity, as is the use of non-participating protecting groups on O -2 and O -3 of the donors. It is further demonstrated that the thioglycoside/benzenesulfenyl triflate activation is applicable in the glucoside series, when both armed and disarmed protecting groups are tolerated.
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β selective glucosylation in the absence of neighboring group participation influence of the 3 4 o bisacetal protecting system
Tetrahedron, 2007Co-Authors: David Crich, Venkataraman Subramanian, Thomas K HuttonAbstract:A 3,4-O-bisacetal 2,6-di-O-benzyl protected thioglucoside is converted to the corresponding glucosyl triflate with 1-benzenesulfinyl piperidine and Trifluoromethanesulfonic Anhydride. The moderate to excellent β-selectivity exhibited with this glucosyl triflate with a range of alcohols is generally higher than that observed with the more electronically disarmed corresponding 3,4-O-carbonate, for which a possible reason is advanced.
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efficient glycosidation of a phenyl thiosialoside donor with diphenyl sulfoxide and triflic Anhydride in dichloromethane
Organic Letters, 2006Co-Authors: David CrichAbstract:The formation of sialic acid glycosides with a thiosialic acid derivative, diphenyl sulfoxide, and Trifluoromethanesulfonic Anhydride is reported. With an excess of diphenyl sulfoxide, glycal formation can be completely suppressed and excellent yields are obtained for coupling to a wide range of primary, secondary, and tertiary acceptors.
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improved synthesis of 1 benzenesulfinyl piperidine and analogs for the activation of thioglycosides in conjunction with Trifluoromethanesulfonic Anhydride
Journal of Carbohydrate Chemistry, 2005Co-Authors: David Crich, Abhisek Banerjee, Qingjia YaoAbstract:An improved protocol for the large‐scale production of 1‐benzenesulfinyl piperidine and other sulfinamides is described. It is demonstrated that 1‐benzenesulfinyl pyrrolidine and N,N‐diethyl benzenesulfinamide function analogously to 1‐benzenesulfinyl piperidine in the Trifluoromethanesulfonic Anhydride‐mediated activation of thioglycosides, and that their less crystalline nature enables them to be used at −78°C as opposed to the −60°C required to keep 1‐benzenesulfinyl piperidine in solution. N,N-Dicyclohexyl benzenesulfinamide does not activate thioglycosides in combination with Trifluoromethanesulfonic Anhydride, which is attributed to its greater steric bulk. * Dedicated with respect to the memory of Professor Jacques H. Van Boom.
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cyclofunctionalization of unsaturated alcohols phenols acids and sulfonamides with 1 benzenesulfinyl piperidine and Trifluoromethanesulfonic Anhydride
Heterocycles, 2004Co-Authors: David Crich, Bhushan Surve, Mousumi SannigrahiAbstract:The combination of a benzenesulfinamide, Trifluoromethanesulfonic Anhydride, and Hunig's base brings about the cyclofunctionalization of unsaturated alcohols, phenols, acids, and sulfonamides to give the corresponding α-phenylsulfanylmethyl cyclic ethers, lactones and sulfonamides, respectively. In an unanticipated twist the products are isolated at the sulfur (II) oxidation state denoting an overall reduction in the oxidation state of the sulfur based electrophile in the course of the reaction.
Teruaki Mukaiyama - One of the best experts on this subject based on the ideXlab platform.
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a facile one pot benzylation of sodium enolates using Trifluoromethanesulfonic Anhydride and diphenyl sulfoxide
Chemical & Pharmaceutical Bulletin, 2005Co-Authors: Tomofumi Takuwa, Tomofumi Minowa, Hidehiko Fujisawa, Teruaki MukaiyamaAbstract:A facile one-pot C-benzylation of various sodium enolates derived from methyl malonate, β-ketoesters, a β-cyanoester, a β-cyanosulfone, ketones and a carboxylic ester is reported. Reaction of alkoxydiphenylsulfonium salts formed by treating various benzyl alcohols with diphenyl sulfide bis(trifluoromethanesulfonate) (derived from Trifluoromethanesulfonic Anhydride and diphenyl sulfoxide) proceeded smoothly, and the corresponding C-benzylated products were afforded in good to high yields.
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facile one pot syntheses of amidines and enamines from oximes via beckmann rearrangement using Trifluoromethanesulfonic Anhydride
Bulletin of the Chemical Society of Japan, 2004Co-Authors: Tomofumi Takuwa, Tomofumi Minowa, Jim Yoshitaka Onishi, Teruaki MukaiyamaAbstract:Iminocarbocation intermediates were in situ-generated by treating various oximes with Trifluoromethanesulfonic Anhydride (Tf2O) in the presence of triethylamine in toluene and nucleophilic trapping...
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an efficient method for the stereoselective synthesis of β d and α d ribofuranosides from 2 3 5 tri o benzyl d ribofuranose by the use of catecholato 2 o o oxotitanium and Trifluoromethanesulfonic Anhydride
ChemInform, 1993Co-Authors: Shinji Suda, Teruaki MukaiyamaAbstract:β-D-Ribofuranosides are stereoselectively synthesized in high yields directly from 2,3,5-tri-O-benzyl-D-ribofuranose and trimethylsilylated nucleophiles by the use of [catecholato(2−)-O,O′ ]oxotitanium and Trifluoromethanesulfonic Anhydride, while α-D-ribofuranosides are prepared predominantly in high yields in the coexistence of lithium perchlorate.
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an efficient method for the stereoselective synthesis of 1 2 cis and 1 2 trans ribofuranosides from 1 hydroxy ribofuranose by the use of diphenyltin sulfide and Trifluoromethanesulfonic Anhydride
ChemInform, 1992Co-Authors: Teruaki Mukaiyama, Koki Matsubara, Shinji SudaAbstract:1,2-trans-Ribofuranosides are stereoselectively synthesized in high yields directly from 1-hydroxy ribofuranose and trimethylsilylated nucleophiles by the use of diphenyltin sulfide and Trifluoromethanesulfonic Anhydride. Even further, in the coexistence of lithium perchlorate, 1,2-cis-ribofuranosides are prepared predominantly in high yields.
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stereoselective synthesis of 1 2 trans ribofuranosides from 1 hydroxy sugars by the use of 1 2 benzenediolato 2 o o oxotitanium and Trifluoromethanesulfonic Anhydride
ChemInform, 1992Co-Authors: Shinji Suda, Teruaki MukaiyamaAbstract:A convenient method for stereoselective synthesis of 1,2-trans-ribofuranosides directly from 1-hydroxy sugars and alcohols or trimethylsilylated nucleophiles by the use of [1,2-benzenediolato(2−)-O,O′]oxotitanium and Trifluoromethanesulfonic Anhydride is described.
George A. Olah - One of the best experts on this subject based on the ideXlab platform.
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Aromatic Nitration with Nitric Acid/Trifluoromethanesulfonic Anhydride
Synthesis, 2002Co-Authors: George A. Olah, Prakash Reddy, G. K. Surya PrakashAbstract:Nitric acid/Trifluoromethanesulfonic (triflic) Anhydride was shown to be a highly effective electrophilic nitrating agent. A series of aromatics were nitrated under mild conditions in high yields. Similar results were also obtained when using nitric acid/trifluoromethane-sulfonic acid/phosphorus pentoxide as nitrating agent in nitroethane or nitromethane solution. The 15 N NMR spectrum of 15 N enriched nitric acid in triflic Anhydride was studied and compared with that of other nitrating reagents. The data indicate the predominantly covalent nature of trifluoromethanesulfonyl nitrate formed in the systems
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aromatic nitration with nitric acid Trifluoromethanesulfonic Anhydride
Synthesis, 1992Co-Authors: George A. Olah, Prakash Reddy, G Surya K PrakashAbstract:Nitric acid/Trifluoromethanesulfonic (triflic) Anhydride was shown to be a highly effective electrophilic nitrating agent. A series of aromatics were nitrated under mild conditions in high yields. Similar results were also obtained when using nitric acid/trifluoromethane-sulfonic acid/phosphorus pentoxide as nitrating agent in nitroethane or nitromethane solution. The 15 N NMR spectrum of 15 N enriched nitric acid in triflic Anhydride was studied and compared with that of other nitrating reagents. The data indicate the predominantly covalent nature of trifluoromethanesulfonyl nitrate formed in the systems
Veronique Gouverneur - One of the best experts on this subject based on the ideXlab platform.
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18f trifluoromethylation of unmodified peptides with 5 18f trifluoromethyl dibenzothiophenium trifluoromethanesulfonate
Journal of the American Chemical Society, 2018Co-Authors: Stefan Verhoog, Choon Wee Kee, Yanlan Wang, Tanatorn Khotavivattana, Thomas C Wilson, Veerle Kersemans, Sean Smart, Matthew Tredwell, Benjamin G Davis, Veronique GouverneurAbstract:The 18F-labeling of 5-(trifluoromethyl)-dibenzothiophenium trifluoromethanesulfonate, commonly referred to as the Umemoto reagent, has been accomplished applying a halogen exchange 18F-fluorination with 18F-fluoride, followed by oxidative cyclization with Oxone and Trifluoromethanesulfonic Anhydride. This new 18F-reagent allows for the direct chemoselective 18F-labeling of unmodified peptides at the thiol cysteine residue.
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18F‑Trifluoromethylation of Unmodified Peptides with 5-18F‑(Trifluoromethyl)dibenzothiophenium Trifluoromethanesulfonate
2018Co-Authors: Stefan Verhoog, Choon Wee Kee, Yanlan Wang, Tanatorn Khotavivattana, Thomas C Wilson, Veerle Kersemans, Sean Smart, Matthew Tredwell, Benjamin G Davis, Veronique GouverneurAbstract:The 18F-labeling of 5-(trifluoromethyl)-dibenzothiophenium trifluoromethanesulfonate, commonly referred to as the Umemoto reagent, has been accomplished applying a halogen exchange 18F-fluorination with 18F-fluoride, followed by oxidative cyclization with Oxone and Trifluoromethanesulfonic Anhydride. This new 18F-reagent allows for the direct chemoselective 18F-labeling of unmodified peptides at the thiol cysteine residue
Kwan Soo Kim - One of the best experts on this subject based on the ideXlab platform.
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Direct glycosylation with anomeric hydroxy sugars by activation with 3-fluorophthalic Anhydride and Trifluoromethanesulfonic Anhydride
Tetrahedron Letters, 2010Co-Authors: Ju Yuel Baek, Boyoung Lee, Rita Pal, Won-yong Lee, Kwan Soo KimAbstract:An efficient and direct one-pot glycosylation method using anomeric hydroxy sugars as glycosyl donors, employing 3-fluorophthalic Anhydride and triflic Anhydride as activating agents, has been developed. The present glycosylation utilizing 3-fluorophthalic Anhydride resulted in few to no undesired self-condensed esters than the glycosylation using phthalic Anhydride. Intermediates in the present glycosylation were identified by an NMR study.
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stereoselective direct glycosylation with anomeric hydroxy sugars by activation with phthalic Anhydride and Trifluoromethanesulfonic Anhydride involving glycosyl phthalate intermediates
Journal of the American Chemical Society, 2008Co-Authors: Kwan Soo Kim, Dinanath Baburao Fulse, Ju Yuel Baek, Boyoung Lee, Heung Bae JeonAbstract:An efficient direct one-pot glycosylation method with anomeric hydroxy sugars as glycosyl donors employing phthalic Anhydride and triflic Anhydride as activating agents has been developed. Thus, highly stereoselective beta-mannopyranosylations were achieved by the reaction of 2,3-di-O-benzyl-4,6-O-benzylidene-D-mannopyranose (2) with phthalic Anhydride in the presence of DBU at room temperature followed by sequential addition of DTBMP and Tf2O and glycosyl acceptors to the reaction mixture at -78 degrees C in one-pot. Stereoselective alpha-glucopyranosylations with 2,3-di-O-benzyl-4,6-O-benzylidene-D-glucopyranose (25) and other glycosylations with glucopyranoses and mannopyranoses having tetra-O-benzyl- and tetra-O-benzoyl protecting groups were also possible by utilizing the present one-pot glycosylation protocol. The possible mechanism for the beta-mannosylation with 2 was proposed based on the NMR study, in which alpha-mannosyl phthalate 55alpha and alpha-mannosyl triflate 59 were detected as intermediates. The versatility and efficiency of the present glycosylation methodology, especially those of the beta-mannopyranosylation protocol, were readily demonstrated by the efficient synthesis of protected beta-(1-->4)-D-mannotriose 62 and beta-(1-->4)-D-mannotetraose 67 with perfect beta-stereoselectivity.
