The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform
Kevin M. Weeks - One of the best experts on this subject based on the ideXlab platform.
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Time-resolved RNA SHAPE chemistry: quantitative RNA structure analysis in one-second snapshots and at single-nucleotide resolution
Nature Protocols, 2009Co-Authors: Stefanie A Mortimer, Kevin M. WeeksAbstract:RNA selective 2′-hydroxyl acylation analyzed by primer extension (SHAPE) chemistry exploits the discovery that conformationally dynamic nucleotides preferentially adopt configurations that facilitate reaction between the 2′-OH group and a hydroxyl-selective electrophile, such as Benzoyl Cyanide (BzCN), to form a 2′- O -adduct. BzCN is ideally suited for quantitative, time-resolved analysis of RNA folding and ribonucleoprotein (RNP) assembly mechanisms because this reagent both reacts with flexible RNA nucleotides and also undergoes auto-inactivating hydrolysis with a half-life of 0.25 s at 37 °C. RNA folding is initiated by addition of Mg^2+ or protein, or other change in solution conditions, and nucleotide resolution structural images are obtained by adding aliquots of the evolving reaction to BzCN and then 'waiting' for 1 second. Sites of the 2′- O -adduct formation are subsequently scored as stops to primer extension using reverse transcriptase. This time-resolved SHAPE protocol makes it possible to obtain 1-second structural snapshots in time-resolved kinetic studies for RNAs of arbitrary length and complexity in a straightforward and concise experiment.
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Time-resolved RNA SHAPE chemistry: quantitative RNA structure analysis in one-second snapshots and at single-nucleotide resolution
Nature protocols, 2009Co-Authors: Stefanie Mortimer, Kevin M. WeeksAbstract:RNA selective 2'-hydroxyl acylation analyzed by primer extension (SHAPE) chemistry exploits the discovery that conformationally dynamic nucleotides preferentially adopt configurations that facilitate reaction between the 2'-OH group and a hydroxyl-selective electrophile, such as Benzoyl Cyanide (BzCN), to form a 2'-O-adduct. BzCN is ideally suited for quantitative, time-resolved analysis of RNA folding and ribonucleoprotein (RNP) assembly mechanisms because this reagent both reacts with flexible RNA nucleotides and also undergoes auto-inactivating hydrolysis with a half-life of 0.25 s at 37 degrees C. RNA folding is initiated by addition of Mg(2+) or protein, or other change in solution conditions, and nucleotide resolution structural images are obtained by adding aliquots of the evolving reaction to BzCN and then 'waiting' for 1 second. Sites of the 2'-O-adduct formation are subsequently scored as stops to primer extension using reverse transcriptase. This time-resolved SHAPE protocol makes it possible to obtain 1-second structural snapshots in time-resolved kinetic studies for RNAs of arbitrary length and complexity in a straightforward and concise experiment.
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Time-resolved RNA SHAPE Chemistry
Journal of the American Chemical Society, 2008Co-Authors: Stefanie Mortimer, Kevin M. WeeksAbstract:Selective 2′-hydroxyl acylation analyzed by primer extension (SHAPE) chemistry yields quantitative RNA secondary and tertiary structure information at single nucleotide resolution. SHAPE takes advantage of the discovery that the nucleophilic reactivity of the ribose 2′-hydroxyl group is modulated by local nucleotide flexibility in the RNA backbone. Flexible nucleotides are reactive toward hydroxyl-selective electrophiles, whereas constrained nucleotides are unreactive. Initial versions of SHAPE chemistry, which employ isatoic anhydride derivatives that react on the minute time scale, are emerging as the ideal technology for monitoring equilibrium structures of RNA in a wide variety of biological environments. Here, we extend SHAPE chemistry to a Benzoyl Cyanide scaffold to make possible facile time-resolved kinetic studies of RNA in ∼1 s snapshots. We then use SHAPE chemistry to follow the time-dependent folding of an RNase P specificity domain RNA. Tertiary interactions form in two distinct steps with lo...
Zhizhong Sun - One of the best experts on this subject based on the ideXlab platform.
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cu tfa 2 catalyzed picolinamido directed c sp2 h cyanation of naphthalenes by using Benzoyl Cyanide as a cyano source
Asian Journal of Organic Chemistry, 2017Co-Authors: He Song, Xiaochong Liu, Chenglong Wang, Jingyi Qiao, Wenyi Chu, Zhizhong SunAbstract:A new protocol for Cu(TFA)2-catalyzed picolinamido-directed C8-H cyanation of naphthalene derivatives with Benzoyl Cyanide as cyano source was developed. A series of 8-cyano-1-(picolinamido)naphthalene derivatives were facilely and conveniently obtained in moderate to good yields by using this method. There were 10 new compounds in the synthesized 22 Cyanide products. In this reaction, Benzoyl Cyanide as cyano source was originally employed to the C(sp2)-H cyanation of the arenes, and the picolinamide moiety as the directing group played a critical role in cyanation of naphthalenes.
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Cu(TFA)2‐Catalyzed Picolinamido‐Directed C(sp2)−H Cyanation of Naphthalenes by Using Benzoyl Cyanide as a Cyano Source
Asian Journal of Organic Chemistry, 2017Co-Authors: He Song, Xiaochong Liu, Chenglong Wang, Jingyi Qiao, Wenyi Chu, Zhizhong SunAbstract:A new protocol for Cu(TFA)2-catalyzed picolinamido-directed C8-H cyanation of naphthalene derivatives with Benzoyl Cyanide as cyano source was developed. A series of 8-cyano-1-(picolinamido)naphthalene derivatives were facilely and conveniently obtained in moderate to good yields by using this method. There were 10 new compounds in the synthesized 22 Cyanide products. In this reaction, Benzoyl Cyanide as cyano source was originally employed to the C(sp2)-H cyanation of the arenes, and the picolinamide moiety as the directing group played a critical role in cyanation of naphthalenes.
He Song - One of the best experts on this subject based on the ideXlab platform.
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cu tfa 2 catalyzed picolinamido directed c sp2 h cyanation of naphthalenes by using Benzoyl Cyanide as a cyano source
Asian Journal of Organic Chemistry, 2017Co-Authors: He Song, Xiaochong Liu, Chenglong Wang, Jingyi Qiao, Wenyi Chu, Zhizhong SunAbstract:A new protocol for Cu(TFA)2-catalyzed picolinamido-directed C8-H cyanation of naphthalene derivatives with Benzoyl Cyanide as cyano source was developed. A series of 8-cyano-1-(picolinamido)naphthalene derivatives were facilely and conveniently obtained in moderate to good yields by using this method. There were 10 new compounds in the synthesized 22 Cyanide products. In this reaction, Benzoyl Cyanide as cyano source was originally employed to the C(sp2)-H cyanation of the arenes, and the picolinamide moiety as the directing group played a critical role in cyanation of naphthalenes.
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Cu(TFA)2‐Catalyzed Picolinamido‐Directed C(sp2)−H Cyanation of Naphthalenes by Using Benzoyl Cyanide as a Cyano Source
Asian Journal of Organic Chemistry, 2017Co-Authors: He Song, Xiaochong Liu, Chenglong Wang, Jingyi Qiao, Wenyi Chu, Zhizhong SunAbstract:A new protocol for Cu(TFA)2-catalyzed picolinamido-directed C8-H cyanation of naphthalene derivatives with Benzoyl Cyanide as cyano source was developed. A series of 8-cyano-1-(picolinamido)naphthalene derivatives were facilely and conveniently obtained in moderate to good yields by using this method. There were 10 new compounds in the synthesized 22 Cyanide products. In this reaction, Benzoyl Cyanide as cyano source was originally employed to the C(sp2)-H cyanation of the arenes, and the picolinamide moiety as the directing group played a critical role in cyanation of naphthalenes.
Richard R Schmidt - One of the best experts on this subject based on the ideXlab platform.
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regioselective Benzoylation of unprotected β glycopyranosides with Benzoyl Cyanide and an amine catalyst application to saponin synthesis
Organic chemistry frontiers, 2021Co-Authors: Yajing Sun, Richard R Schmidt, Fengshan Wang, Hongxiang Lou, Yue Yang, Peng PengAbstract:Protection of totally unprotected β-D-gluco-, β-D-quinovo- and β-D-xylopyranosides with BzCN and Et3N as the catalyst afforded directly and regioselectively 3,6-di-O-Benzoylated β-D-glucopyranosides or 3-O-Benzoylated β-D-quinovo- and β-D-xylopyranosides, respectively. Furthermore, these trans–trans triol and tetrol systems could be regioselectively transformed into their corresponding 2-O-unprotected derivatives in the presence of BzCN as the Benzoylating agent and a catalytic amount of 4-pyrrolidinopyridine as a base in one-pot reactions. Hence, BzCN in the presence of a catalytic amount of an amine base exhibits unique properties as an acylating agent, permitting the regioselective protection of all diol, triol and tetrol stereostructures occurring in the commonly found glycopyranosides. The convenient access and great value of some of the derived building blocks are shown through the concise synthesis of natural and unnatural saponins.
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Regioselective Benzoylation of unprotected β-glycopyranosides with Benzoyl Cyanide and an amine catalyst – application to saponin synthesis
Organic Chemistry Frontiers, 2021Co-Authors: Yajing Sun, Richard R Schmidt, Yang Yue, Fengshan Wang, Hongxiang Lou, Peng PengAbstract:Protection of totally unprotected β-D-gluco-, β-D-quinovo- and β-D-xylopyranosides with BzCN and Et3N as the catalyst afforded directly and regioselectively 3,6-di-O-Benzoylated β-D-glucopyranosides or 3-O-Benzoylated β-D-quinovo- and β-D-xylopyranosides, respectively. Furthermore, these trans–trans triol and tetrol systems could be regioselectively transformed into their corresponding 2-O-unprotected derivatives in the presence of BzCN as the Benzoylating agent and a catalytic amount of 4-pyrrolidinopyridine as a base in one-pot reactions. Hence, BzCN in the presence of a catalytic amount of an amine base exhibits unique properties as an acylating agent, permitting the regioselective protection of all diol, triol and tetrol stereostructures occurring in the commonly found glycopyranosides. The convenient access and great value of some of the derived building blocks are shown through the concise synthesis of natural and unnatural saponins.
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regioselective acylation of diols and triols the Cyanide effect
Journal of the American Chemical Society, 2016Co-Authors: Peng Peng, Michael Linseis, Rainer F Winter, Richard R SchmidtAbstract:Central topics of carbohydrate chemistry embrace structural modifications of carbohydrates and oligosaccharide synthesis. Both require regioselectively protected building blocks that are mainly available via indirect multistep procedures. Hence, direct protection methods targeting a specific hydroxy group are demanded. Dual hydrogen bonding will eventually differentiate between differently positioned hydroxy groups. As Cyanide is capable of various kinds of hydrogen bonding and as it is a quite strong sterically nondemanding base, regioselective O-acylations should be possible at low temperatures even at sterically congested positions, thus permitting formation and also isolation of the kinetic product. Indeed, 1,2-cis-diols, having an equatorial and an axial hydroxy group, Benzoyl Cyanide or acetyl Cyanide as an acylating agent, and DMAP as a catalyst yield at −78 °C the thermodynamically unfavorable axial O-acylation product; acyl migration is not observed under these conditions. This phenomenon was sub...
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A simple access to lactose-derived building blocks required in glycoconjugate synthesis
Carbohydrate research, 1997Co-Authors: Luigi Lay, Rainer Windmüller, Stefan Reinhardt, Richard R SchmidtAbstract:Abstract Lactose was readily transformed into thexyldimethylsilyl (3,4-O-isopropylidene- β- d -galactopyranosyl)-(1 → 4)-β- d -glucopyranoside ( 5 ); this compound served as intermediate for the generation of partially O -protected lactose building blocks required in oligosaccharide and glycoconjugate synthesis. Thus, from 5 via per- O -Benzoylation, desilylation, trichloroacetimidate formation, glycosylation of the Lemieux spacer, and acid-catalyzed de- O -isopropylidenation methoxycarbonyloctyl (2.6-di-O-Benzoyl-β- d -galactopyranosyl)-(1 → 4)-2.3.6-tri-O-Benzoyl-β- d - glucopyranoside ( 12 ) was obtained. Regioselective Benzoylation of 5 with Benzoyl Cyanide under various conditions afforded 3- O - (13), 2,3,2′- O - (14), 3,2′- O - (16), and 2,2′- O -unprotected ( 17 ) lactoside, respectively. De- O -isopropylidenation of 16 gave thexyldimethylsilyl (6-O-Benzoyl-β- d -galactopyranosyl)- (1 → 4)-2,6-di-O-Benzoyl-β- d -glucopyranoside ( 18 ), an important 2′,3′,4′- O -unprotected lactose derivative. Fucosylation of 13 and then de- O -isopropylidenation afforded thexyldimethylsilyl (2,6-di-O-Benzoyl-β- d -galactopyranosyl)-(1 → 4)-[(3,4-di- O-acetyl-2-O-Benzoyl-α- l -fucopyranosyl)-(1 → 3)]-2,6-di-O- Benzoyl-β- d -glucopyranoside( 21 ), an important fucosyllactose building block.
Peng Peng - One of the best experts on this subject based on the ideXlab platform.
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regioselective Benzoylation of unprotected β glycopyranosides with Benzoyl Cyanide and an amine catalyst application to saponin synthesis
Organic chemistry frontiers, 2021Co-Authors: Yajing Sun, Richard R Schmidt, Fengshan Wang, Hongxiang Lou, Yue Yang, Peng PengAbstract:Protection of totally unprotected β-D-gluco-, β-D-quinovo- and β-D-xylopyranosides with BzCN and Et3N as the catalyst afforded directly and regioselectively 3,6-di-O-Benzoylated β-D-glucopyranosides or 3-O-Benzoylated β-D-quinovo- and β-D-xylopyranosides, respectively. Furthermore, these trans–trans triol and tetrol systems could be regioselectively transformed into their corresponding 2-O-unprotected derivatives in the presence of BzCN as the Benzoylating agent and a catalytic amount of 4-pyrrolidinopyridine as a base in one-pot reactions. Hence, BzCN in the presence of a catalytic amount of an amine base exhibits unique properties as an acylating agent, permitting the regioselective protection of all diol, triol and tetrol stereostructures occurring in the commonly found glycopyranosides. The convenient access and great value of some of the derived building blocks are shown through the concise synthesis of natural and unnatural saponins.
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Regioselective Benzoylation of unprotected β-glycopyranosides with Benzoyl Cyanide and an amine catalyst – application to saponin synthesis
Organic Chemistry Frontiers, 2021Co-Authors: Yajing Sun, Richard R Schmidt, Yang Yue, Fengshan Wang, Hongxiang Lou, Peng PengAbstract:Protection of totally unprotected β-D-gluco-, β-D-quinovo- and β-D-xylopyranosides with BzCN and Et3N as the catalyst afforded directly and regioselectively 3,6-di-O-Benzoylated β-D-glucopyranosides or 3-O-Benzoylated β-D-quinovo- and β-D-xylopyranosides, respectively. Furthermore, these trans–trans triol and tetrol systems could be regioselectively transformed into their corresponding 2-O-unprotected derivatives in the presence of BzCN as the Benzoylating agent and a catalytic amount of 4-pyrrolidinopyridine as a base in one-pot reactions. Hence, BzCN in the presence of a catalytic amount of an amine base exhibits unique properties as an acylating agent, permitting the regioselective protection of all diol, triol and tetrol stereostructures occurring in the commonly found glycopyranosides. The convenient access and great value of some of the derived building blocks are shown through the concise synthesis of natural and unnatural saponins.
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regioselective acylation of diols and triols the Cyanide effect
Journal of the American Chemical Society, 2016Co-Authors: Peng Peng, Michael Linseis, Rainer F Winter, Richard R SchmidtAbstract:Central topics of carbohydrate chemistry embrace structural modifications of carbohydrates and oligosaccharide synthesis. Both require regioselectively protected building blocks that are mainly available via indirect multistep procedures. Hence, direct protection methods targeting a specific hydroxy group are demanded. Dual hydrogen bonding will eventually differentiate between differently positioned hydroxy groups. As Cyanide is capable of various kinds of hydrogen bonding and as it is a quite strong sterically nondemanding base, regioselective O-acylations should be possible at low temperatures even at sterically congested positions, thus permitting formation and also isolation of the kinetic product. Indeed, 1,2-cis-diols, having an equatorial and an axial hydroxy group, Benzoyl Cyanide or acetyl Cyanide as an acylating agent, and DMAP as a catalyst yield at −78 °C the thermodynamically unfavorable axial O-acylation product; acyl migration is not observed under these conditions. This phenomenon was sub...