The Experts below are selected from a list of 3855 Experts worldwide ranked by ideXlab platform
Wenhu Duan - One of the best experts on this subject based on the ideXlab platform.
-
Selective Debenzylation of benzyl esters by silica-supported sodium hydrogen sulphate
Chinese Chemical Letters, 2009Co-Authors: Yan Wei Hu, De Yong Ye, Wenhu DuanAbstract:Abstract A new Debenzylation of benzyl esters by silica-supported sodium hydrogen sulfate is described. The Debenzylation could be achieved selectively and efficiently in good to excellent yields without affecting sensitive functional groups such as nitro, unsaturated bonds, and ethyl ester.
-
Selective Debenzylation of aromatic benzyl ethers by silica-supported sodium hydrogen sulfate
Tetrahedron Letters, 2008Co-Authors: Linna Zhou, Wenjing Wang, Li Zuo, Shanyan Yao, Wei Wang, Wenhu DuanAbstract:A new Debenzylation of aromatic benzyl ethers by silica-supported sodium hydrogen sulfate is described. The process proceeds selectively and efficiently in good to excellent yields without affecting sensitive functional groups such as nitro, COOMe, aldehyde, ketone, and tosyl.
Stephen G. Davies - One of the best experts on this subject based on the ideXlab platform.
-
the asymmetric syntheses of pyrrolizidines indolizidines and quinolizidines via two sequential tandem ring closure n Debenzylation processes
Organic and Biomolecular Chemistry, 2014Co-Authors: Stephen G. Davies, Paul. M. Roberts, Ai M. Fletcher, Emma M. Foster, Ian T. T. Houlsby, Thomas M. Schofield, James E. ThomsonAbstract:Concise asymmetric syntheses of (−)-lupinine, (+)-isoretronecanol, (+)-5-epi-tashiromine and (R,R)-1-(hydroxymethyl)octahydroindolizine (the azabicyclic core within stellettamides A–C) have been achieved in 8 steps or fewer from commercially available starting materials. The key steps in these syntheses involved the preparation of enantiopure β-amino esters, upon conjugate addition of lithium (R)-N-(p-methoxybenzyl)-N-(α-methyl-p-methoxybenzyl)amide to either ζ-chloro or ζ-hydroxy substituted tert-butyl (E)-hept-2-enoate, or e-chloro or e-hydroxy substituted tert-butyl (E)-hex-2-enoate. Activation of the ω-substituent as a leaving group led to SN2-type ring-closure, which occurred with concomitant N-Debenzylation via an E1-type deprotection step, to give the corresponding pyrrolidine or piperidine in good yield. Subsequent alkylation of these enantiopure azacycles, followed by a second ring-closure/concomitant N-Debenzylation step formed the pyrrolizidine, indolizidine or quinolizidine motif, and reduction with LiAlH4 gave the target compounds in diastereoisomerically and enantiomerically pure form.
-
The asymmetric syntheses of pyrrolizidines, indolizidines and quinolizidines via two sequential tandem ring-closure/N-Debenzylation processes
Organic & biomolecular chemistry, 2014Co-Authors: Stephen G. Davies, Paul. M. Roberts, Ai M. Fletcher, Emma M. Foster, Ian T. T. Houlsby, Thomas M. Schofield, James E. ThomsonAbstract:Concise asymmetric syntheses of (−)-lupinine, (+)-isoretronecanol, (+)-5-epi-tashiromine and (R,R)-1-(hydroxymethyl)octahydroindolizine (the azabicyclic core within stellettamides A–C) have been achieved in 8 steps or fewer from commercially available starting materials. The key steps in these syntheses involved the preparation of enantiopure β-amino esters, upon conjugate addition of lithium (R)-N-(p-methoxybenzyl)-N-(α-methyl-p-methoxybenzyl)amide to either ζ-chloro or ζ-hydroxy substituted tert-butyl (E)-hept-2-enoate, or e-chloro or e-hydroxy substituted tert-butyl (E)-hex-2-enoate. Activation of the ω-substituent as a leaving group led to SN2-type ring-closure, which occurred with concomitant N-Debenzylation via an E1-type deprotection step, to give the corresponding pyrrolidine or piperidine in good yield. Subsequent alkylation of these enantiopure azacycles, followed by a second ring-closure/concomitant N-Debenzylation step formed the pyrrolizidine, indolizidine or quinolizidine motif, and reduction with LiAlH4 gave the target compounds in diastereoisomerically and enantiomerically pure form.
-
Iodine-mediated Ring Closing Alkene Iodoamination with N-Debenzylation for the Asymmetric Synthesis of Polyhydroxylated Pyrrolidines
Synlett, 2004Co-Authors: Stephen G. Davies, Rebecca L. Nicholson, Paul D. Price, Paul. M. Roberts, Andrew D. SmithAbstract:An iodine-mediated ring closing alkene iodoamination with N-Debenzylation protocol provides a direct route for the asymmetric synthesis of polyhydroxylated pyrrolidines from homochiral β-amino acid derivatives
-
Chemoselective Debenzylation of N-benzyl tertiary amines with ceric ammonium nitrate
Journal of the Chemical Society Perkin Transactions 1, 2000Co-Authors: Steven D. Bull, Stephen G. Davies, Garry Fenton, Andrew W. Mulvaney, R. Shyam Prasad, Andrew D. SmithAbstract:Treatment of a range of N-benzyl tertiary amines with aqueous ceric ammonium nitrate results in N-Debenzylation to afford the corresponding secondary amine. Chemoselective mono-N-Debenzylation of N-benzyl tertiary amines is shown to occur in the presence of N-benzyl amides, O-benzyl ethers, O-benzyl esters, O-benzyl phenolates and S-benzyl ethers.
-
Chemoselective oxidative Debenzylation of tertiary N-benzyl amines
Chemical Communications, 2000Co-Authors: Steven D. Bull, Stephen G. Davies, Garry Fenton, Andrew W. Mulvaney, R. Shyam Prasad, Andrew D. SmithAbstract:Treatment of tertiary amines containing one or more N-benzyl protecting groups with aqueous ceric ammonium nitrate results in clean N-Debenzylation to afford the corresponding secondary amine.
Hidetoshi Yamada - One of the best experts on this subject based on the ideXlab platform.
-
facile and regioselective preparation of partly o benzylated d glucopyranose acetates via acid mediated simultaneous Debenzylation acetolysis
Carbohydrate Research, 2006Co-Authors: Yang Cao, Yasunori Okada, Hidetoshi YamadaAbstract:Abstract Fully O-benzylated methyl α- d -glucopyranoside shows a steady order in stepwise Debenzylation when it is treated with sulfuric acid in acetic anhydride. Based on the order of Debenzylation, regioselective preparations of 2,3,4-tri-, 2,3-, 2,4-, 3,4-di-, and 2- O -benzyl- d -glucopyranose acetates were facilitated in greater than 80% yields. The key points of the preparative reactions were the control of the acid strength and choice of suitable substrates.
-
Facile and regioselective preparation of partly O-benzylated d-glucopyranose acetates via acid-mediated simultaneous Debenzylation–acetolysis
Carbohydrate research, 2006Co-Authors: Yang Cao, Yasunori Okada, Hidetoshi YamadaAbstract:Abstract Fully O-benzylated methyl α- d -glucopyranoside shows a steady order in stepwise Debenzylation when it is treated with sulfuric acid in acetic anhydride. Based on the order of Debenzylation, regioselective preparations of 2,3,4-tri-, 2,3-, 2,4-, 3,4-di-, and 2- O -benzyl- d -glucopyranose acetates were facilitated in greater than 80% yields. The key points of the preparative reactions were the control of the acid strength and choice of suitable substrates.
James E. Thomson - One of the best experts on this subject based on the ideXlab platform.
-
the asymmetric syntheses of pyrrolizidines indolizidines and quinolizidines via two sequential tandem ring closure n Debenzylation processes
Organic and Biomolecular Chemistry, 2014Co-Authors: Stephen G. Davies, Paul. M. Roberts, Ai M. Fletcher, Emma M. Foster, Ian T. T. Houlsby, Thomas M. Schofield, James E. ThomsonAbstract:Concise asymmetric syntheses of (−)-lupinine, (+)-isoretronecanol, (+)-5-epi-tashiromine and (R,R)-1-(hydroxymethyl)octahydroindolizine (the azabicyclic core within stellettamides A–C) have been achieved in 8 steps or fewer from commercially available starting materials. The key steps in these syntheses involved the preparation of enantiopure β-amino esters, upon conjugate addition of lithium (R)-N-(p-methoxybenzyl)-N-(α-methyl-p-methoxybenzyl)amide to either ζ-chloro or ζ-hydroxy substituted tert-butyl (E)-hept-2-enoate, or e-chloro or e-hydroxy substituted tert-butyl (E)-hex-2-enoate. Activation of the ω-substituent as a leaving group led to SN2-type ring-closure, which occurred with concomitant N-Debenzylation via an E1-type deprotection step, to give the corresponding pyrrolidine or piperidine in good yield. Subsequent alkylation of these enantiopure azacycles, followed by a second ring-closure/concomitant N-Debenzylation step formed the pyrrolizidine, indolizidine or quinolizidine motif, and reduction with LiAlH4 gave the target compounds in diastereoisomerically and enantiomerically pure form.
-
The asymmetric syntheses of pyrrolizidines, indolizidines and quinolizidines via two sequential tandem ring-closure/N-Debenzylation processes
Organic & biomolecular chemistry, 2014Co-Authors: Stephen G. Davies, Paul. M. Roberts, Ai M. Fletcher, Emma M. Foster, Ian T. T. Houlsby, Thomas M. Schofield, James E. ThomsonAbstract:Concise asymmetric syntheses of (−)-lupinine, (+)-isoretronecanol, (+)-5-epi-tashiromine and (R,R)-1-(hydroxymethyl)octahydroindolizine (the azabicyclic core within stellettamides A–C) have been achieved in 8 steps or fewer from commercially available starting materials. The key steps in these syntheses involved the preparation of enantiopure β-amino esters, upon conjugate addition of lithium (R)-N-(p-methoxybenzyl)-N-(α-methyl-p-methoxybenzyl)amide to either ζ-chloro or ζ-hydroxy substituted tert-butyl (E)-hept-2-enoate, or e-chloro or e-hydroxy substituted tert-butyl (E)-hex-2-enoate. Activation of the ω-substituent as a leaving group led to SN2-type ring-closure, which occurred with concomitant N-Debenzylation via an E1-type deprotection step, to give the corresponding pyrrolidine or piperidine in good yield. Subsequent alkylation of these enantiopure azacycles, followed by a second ring-closure/concomitant N-Debenzylation step formed the pyrrolizidine, indolizidine or quinolizidine motif, and reduction with LiAlH4 gave the target compounds in diastereoisomerically and enantiomerically pure form.
Hua Yang - One of the best experts on this subject based on the ideXlab platform.
-
Enantiospecific total synthesis of (+)-tanikolide via a key [2,3]-Meisenheimer rearrangement with an allylic amine N-oxide-directed epoxidation and a one-pot trichloroisocyanuric acid N-Debenzylation and N-chlorination.
The Journal of organic chemistry, 2013Co-Authors: Yangla Xie, Moran Sun, Hang Zhou, Qiwei Cao, Kaige Gao, Changling Niu, Hua YangAbstract:The enantiospecific total synthesis of the δ-lactonic marine natural product (+)-tanikolide (1), isolated from Lyngbya majuscula , was achieved using a [2,3]-Meisenheimer rearrangement as the key reaction. During this rearrangement, we discovered that the allylic amine N-oxide could direct the m-CPBA double-bond epoxidation to the syn position. The resulting syn product 8 underwent epoxide ring opening under the m-CBA conditions to give the five- and six-membered cyclic ether amine N-oxides, which we further treated with Zn and conc. HCl to obtain the reduced bisbenzyl tertiary amines 23 and 22, respectively. When 23 and 22 were treated with trichloroisocyanuric acid (TCCA) in dichloromethane, oxidation at the benzyl position occurred, forming iminium ions. These intermediates were trapped by intramolecular reaction with the hydroxyls, and the resulting intermediates were then oxidized or shifted to afford 25 and 24, respectively. The entire one-pot process involves N-Debenzylation, N-chlorination, and hemiacetal oxidation. The amine N-oxide-directed epoxidation complements Davies' ammonium-directed epoxidation. Thus, TCCA N-Debenzylation is described for the first time and might be a useful N-Debenzylation technique.
-
enantiospecific total synthesis of tanikolide via a key 2 3 meisenheimer rearrangement with an allylic amine n oxide directed epoxidation and a one pot trichloroisocyanuric acid n Debenzylation and n chlorination
Journal of Organic Chemistry, 2013Co-Authors: Yangla Xie, Moran Sun, Hang Zhou, Qiwei Cao, Kaige Gao, Changling Niu, Hua YangAbstract:The enantiospecific total synthesis of the δ-lactonic marine natural product (+)-tanikolide (1), isolated from Lyngbya majuscula , was achieved using a [2,3]-Meisenheimer rearrangement as the key reaction. During this rearrangement, we discovered that the allylic amine N-oxide could direct the m-CPBA double-bond epoxidation to the syn position. The resulting syn product 8 underwent epoxide ring opening under the m-CBA conditions to give the five- and six-membered cyclic ether amine N-oxides, which we further treated with Zn and conc. HCl to obtain the reduced bisbenzyl tertiary amines 23 and 22, respectively. When 23 and 22 were treated with trichloroisocyanuric acid (TCCA) in dichloromethane, oxidation at the benzyl position occurred, forming iminium ions. These intermediates were trapped by intramolecular reaction with the hydroxyls, and the resulting intermediates were then oxidized or shifted to afford 25 and 24, respectively. The entire one-pot process involves N-Debenzylation, N-chlorination, and hemiacetal oxidation. The amine N-oxide-directed epoxidation complements Davies' ammonium-directed epoxidation. Thus, TCCA N-Debenzylation is described for the first time and might be a useful N-Debenzylation technique.
