The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
Hyeung-geun Park - One of the best experts on this subject based on the ideXlab platform.
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Asymmetric synthesis and evaluation of α-quaternary chiral lactam derivatives as novel anticancer agents
Archives of Pharmacal Research, 2014Co-Authors: Su Jung Hwang, Hyeung-geun Park, Suckchang Hong, Jisung Jung, Yo-han ParkAbstract:Asymmetric synthesis of α-quaternary chiral lactam derivatives as novel anticancer agents and evaluation of their cytotoxic potentials and spectrums are reported. Among the developed lactam derivatives, the most active new compounds ( S )- 4m and ( S )- 4n synthesized via asymmetric phase-transfer Catalytic Alkylation in very high optical yields (98 % ee) show promising in vitro anticancer activities with low micromolar IC_50 values against colon, uterus, lung, and breast human cancer cells.
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Highly enantioselective synthesis of 5-phenyl-2-alkylprolines using phase-transfer Catalytic Alkylation
Organic and Biomolecular Chemistry, 2013Co-Authors: Eun Young Park, Yo-han Park, Min Woo Ha, Suckchang Hong, Hyeung-geun ParkAbstract:An efficient enantioselective synthetic method for the synthesis of (2R)-5-phenyl-2-alkylproline tert-butyl esters was reported. The phase-transfer Catalytic Alkylation of tert-butyl-5-phenyl-3,4-dihydro-2H-pyrrole-2-carboxylate in the presence of chiral quaternary ammonium catalysts gave the corresponding alkylated products (up to 97% ee). The following diastereoselective reductions afforded chiral 5-phenyl-2-alkylprolines which can be applied to asymmetric synthesis as organocatalysts or synthesis of biologically active proline based compounds, such as chiral α-alkylated analogues of (+)-RP66803, as potential CCK antagonists.
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Highly Enantioselective Total Synthesis of (+)-Isonitramine
Organic Letters, 2012Co-Authors: Yo-han Park, Suckchang Hong, Hyeung-geun ParkAbstract:A new efficient enantioselective synthetic method of (+)-isonitramine is reported. (+)-Isonitramine was obtained in 12 steps (98% ee and 43% overall yield) from δ-valerolactam via enantioselective phase-transfer Catalytic Alkylation, Dieckman condensation, and diastereoselective reduction as key steps.
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New synthetic route to N-tocopherol derivatives: synthesis of pyrrolopyridinol analogue of α-tocopherol from pyridoxine
Organic and Biomolecular Chemistry, 2011Co-Authors: Jin-mo Ku, Hyeung-geun Park, Ned A. Porter, Byeong-seon JeongAbstract:A new synthetic route to pyrrolopyridinol antioxidants from easily accessible pyridoxine was developed which includes phase-transfer Catalytic Alkylation and intramolecular Cu(I)-catalyzed amination as key steps.
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Synthesis of (-)-Paroxetine via Enantioselective Phase-Transfer Catalytic MonoAlkylation of Malonamide Ester.
ChemInform, 2010Co-Authors: Yo-han Park, Byeong-seon Jeong, Hyeung-geun ParkAbstract:The synthesis is achieved with the enantioselective phase-transfer Catalytic Alkylation to yield (III) and the diastereoselective Michael addition affording (VI) with 96% d.e.
Byeong-seon Jeong - One of the best experts on this subject based on the ideXlab platform.
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New synthetic route to N-tocopherol derivatives: synthesis of pyrrolopyridinol analogue of α-tocopherol from pyridoxine
Organic and Biomolecular Chemistry, 2011Co-Authors: Jin-mo Ku, Hyeung-geun Park, Ned A. Porter, Byeong-seon JeongAbstract:A new synthetic route to pyrrolopyridinol antioxidants from easily accessible pyridoxine was developed which includes phase-transfer Catalytic Alkylation and intramolecular Cu(I)-catalyzed amination as key steps.
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Synthesis of (-)-Paroxetine via Enantioselective Phase-Transfer Catalytic MonoAlkylation of Malonamide Ester.
ChemInform, 2010Co-Authors: Yo-han Park, Byeong-seon Jeong, Hyeung-geun ParkAbstract:The synthesis is achieved with the enantioselective phase-transfer Catalytic Alkylation to yield (III) and the diastereoselective Michael addition affording (VI) with 96% d.e.
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Synthesis of (-)-paroxetine via enantioselective phase-transfer Catalytic monoAlkylation of malonamide ester.
Organic Letters, 2010Co-Authors: Yo-han Park, Byeong-seon Jeong, Hyeung-geun ParkAbstract:A new enantioselective synthetic method of (−)-paroxetine is reported. (−)-Paroxetine could be obtained in 15 steps (95% ee and 9.1% overall yield) from N,N-bis(p-methoxyphenyl)malonamide tert-butyl ester via the enantioselective phase-transfer Catalytic Alkylation and the diastereoselective Michael addition as the key steps.
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Solid-phase synthesis of α-alkylserines via phase-transfer Catalytic Alkylation of polymer-supported 2-phenyl-2-oxazoline-4-carboxylate
Tetrahedron, 2009Co-Authors: Min Woo Ha, Hyeung-geun Park, Jin-mo Ku, Byeong-seon JeongAbstract:Described is the development of a new solid-phase synthetic method for α-alkylserines in which phase-transfer Catalytic Alkylation of polymer-supported 2-phenyl-2-oxazoline-4-carboxylate (12) is the key step. The easy preparation of the polymer-supported substrate 12, the high chemical yield (up to 93%), and the mild cleavage conditions could make this method very practical for the synthesis of α-alkylserines.
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Highly Enantioselective Synthesis of (S)-α-Alkyl-α,β-diaminopropionic Acids via Asymmetric Phase-Transfer Catalytic Alkylation of 2-Phenyl-2-imidazoline-4-carboxylic Acid tert-Butyl Esters
Organic Letters, 2009Co-Authors: Yo-han Park, Byeong-seon Jeong, Sukhoon Kang, Hyeung-geun ParkAbstract:An efficient enantioselective synthetic method for (S)-α-alkyl-α,β-diaminopropionic acid is reported. The asymmetric phase-transfer Catalytic Alkylation of N(1)-Boc-2-phenyl-2-imidazoline-4-carboxylic acid tert -butyl ester in the presence of chiral quaternary ammonium catalyst gave the corresponding alkylated products (93−98% ee) which could be transformed to enantioenriched α-alkyl-α,β-diaminopropionic acids.
Yo-han Park - One of the best experts on this subject based on the ideXlab platform.
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Asymmetric synthesis and evaluation of α-quaternary chiral lactam derivatives as novel anticancer agents
Archives of Pharmacal Research, 2014Co-Authors: Su Jung Hwang, Hyeung-geun Park, Suckchang Hong, Jisung Jung, Yo-han ParkAbstract:Asymmetric synthesis of α-quaternary chiral lactam derivatives as novel anticancer agents and evaluation of their cytotoxic potentials and spectrums are reported. Among the developed lactam derivatives, the most active new compounds ( S )- 4m and ( S )- 4n synthesized via asymmetric phase-transfer Catalytic Alkylation in very high optical yields (98 % ee) show promising in vitro anticancer activities with low micromolar IC_50 values against colon, uterus, lung, and breast human cancer cells.
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Highly enantioselective synthesis of 5-phenyl-2-alkylprolines using phase-transfer Catalytic Alkylation
Organic and Biomolecular Chemistry, 2013Co-Authors: Eun Young Park, Yo-han Park, Min Woo Ha, Suckchang Hong, Hyeung-geun ParkAbstract:An efficient enantioselective synthetic method for the synthesis of (2R)-5-phenyl-2-alkylproline tert-butyl esters was reported. The phase-transfer Catalytic Alkylation of tert-butyl-5-phenyl-3,4-dihydro-2H-pyrrole-2-carboxylate in the presence of chiral quaternary ammonium catalysts gave the corresponding alkylated products (up to 97% ee). The following diastereoselective reductions afforded chiral 5-phenyl-2-alkylprolines which can be applied to asymmetric synthesis as organocatalysts or synthesis of biologically active proline based compounds, such as chiral α-alkylated analogues of (+)-RP66803, as potential CCK antagonists.
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Highly Enantioselective Total Synthesis of (+)-Isonitramine
Organic Letters, 2012Co-Authors: Yo-han Park, Suckchang Hong, Hyeung-geun ParkAbstract:A new efficient enantioselective synthetic method of (+)-isonitramine is reported. (+)-Isonitramine was obtained in 12 steps (98% ee and 43% overall yield) from δ-valerolactam via enantioselective phase-transfer Catalytic Alkylation, Dieckman condensation, and diastereoselective reduction as key steps.
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Synthesis of (-)-Paroxetine via Enantioselective Phase-Transfer Catalytic MonoAlkylation of Malonamide Ester.
ChemInform, 2010Co-Authors: Yo-han Park, Byeong-seon Jeong, Hyeung-geun ParkAbstract:The synthesis is achieved with the enantioselective phase-transfer Catalytic Alkylation to yield (III) and the diastereoselective Michael addition affording (VI) with 96% d.e.
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Synthesis of (-)-paroxetine via enantioselective phase-transfer Catalytic monoAlkylation of malonamide ester.
Organic Letters, 2010Co-Authors: Yo-han Park, Byeong-seon Jeong, Hyeung-geun ParkAbstract:A new enantioselective synthetic method of (−)-paroxetine is reported. (−)-Paroxetine could be obtained in 15 steps (95% ee and 9.1% overall yield) from N,N-bis(p-methoxyphenyl)malonamide tert-butyl ester via the enantioselective phase-transfer Catalytic Alkylation and the diastereoselective Michael addition as the key steps.
Robert R. Knowles - One of the best experts on this subject based on the ideXlab platform.
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Catalytic Alkylation of remote c h bonds enabled by proton coupled electron transfer
Nature, 2016Co-Authors: Gilbert J. Choi, David C. Miller, Carol J. Gu, Robert R. KnowlesAbstract:Catalytic Alkylation of C–H bonds is achieved via homolysis of N–H bonds of N-alkyl amides through proton-coupled electron transfer. In two separate reports, Robert Knowles and colleagues, and John Chu and Tomislav Rovis report the selective homolysis of selected amidyl N–H bonds through a photoCatalytic proton-coupled electron-transfer process. The resulting radical enables C–H abstraction and radical Alkylation at the unactivated 5 position on the aliphatic chain of the N-alkyl amide. As this method does not rely on pre-activation of the amidyl N–H bond or the use of haloamides, it offers a potentially simpler solution than previous approaches to radical amidyls. Additionally, the subsequent 1,5-hydrogen-atom transfer offers a route to selective C–C bond formation in the presence of alkyl amides. Despite advances in hydrogen atom transfer (HAT) catalysis1,2,3,4,5, there are currently no molecular HAT catalysts that are capable of homolysing the strong nitrogen–hydrogen (N–H) bonds of N-alkyl amides. The motivation to develop amide homolysis protocols stems from the utility of the resultant amidyl radicals, which are involved in various synthetically useful transformations, including olefin amination6,7,8,9,10,11 and directed carbon–hydrogen (C–H) bond functionalization12,13,14,15,16. In the latter process—a subset of the classical Hofmann–Loffler–Freytag reaction—amidyl radicals remove hydrogen atoms from unactivated aliphatic C–H bonds17,18,19,20,21. Although powerful, these transformations typically require oxidative N-prefunctionalization of the amide starting materials to achieve efficient amidyl generation. Moreover, because these N-activating groups are often incorporated into the final products, these methods are generally not amenable to the direct construction of carbon–carbon (C–C) bonds. Here we report an approach that overcomes these limitations by homolysing the N–H bonds of N-alkyl amides via proton-coupled electron transfer. In this protocol, an excited-state iridium photocatalyst and a weak phosphate base cooperatively serve to remove both a proton and an electron from an amide substrate in a concerted elementary step. The resultant amidyl radical intermediates are shown to promote subsequent C–H abstraction and radical Alkylation steps. This C–H Alkylation represents a Catalytic variant of the Hofmann–Loffler–Freytag reaction, using simple, unfunctionalized amides to direct the formation of new C–C bonds. Given the prevalence of amides in pharmaceuticals and natural products, we anticipate that this method will simplify the synthesis and structural elaboration of amine-containing targets. Moreover, this study demonstrates that concerted proton-coupled electron transfer can enable homolytic activation of common organic functional groups that are energetically inaccessible using traditional HAT-based approaches.
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Catalytic Alkylation of remote C–H bonds enabled by proton-coupled electron transfer
Nature, 2016Co-Authors: Gilbert J. Choi, David C. Miller, Carol J. Gu, Robert R. KnowlesAbstract:Catalytic Alkylation of C–H bonds is achieved via homolysis of N–H bonds of N-alkyl amides through proton-coupled electron transfer.
Jin-mo Ku - One of the best experts on this subject based on the ideXlab platform.
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New synthetic route to N-tocopherol derivatives: synthesis of pyrrolopyridinol analogue of α-tocopherol from pyridoxine
Organic and Biomolecular Chemistry, 2011Co-Authors: Jin-mo Ku, Hyeung-geun Park, Ned A. Porter, Byeong-seon JeongAbstract:A new synthetic route to pyrrolopyridinol antioxidants from easily accessible pyridoxine was developed which includes phase-transfer Catalytic Alkylation and intramolecular Cu(I)-catalyzed amination as key steps.
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Solid-phase synthesis of α-alkylserines via phase-transfer Catalytic Alkylation of polymer-supported 2-phenyl-2-oxazoline-4-carboxylate
Tetrahedron, 2009Co-Authors: Min Woo Ha, Hyeung-geun Park, Jin-mo Ku, Byeong-seon JeongAbstract:Described is the development of a new solid-phase synthetic method for α-alkylserines in which phase-transfer Catalytic Alkylation of polymer-supported 2-phenyl-2-oxazoline-4-carboxylate (12) is the key step. The easy preparation of the polymer-supported substrate 12, the high chemical yield (up to 93%), and the mild cleavage conditions could make this method very practical for the synthesis of α-alkylserines.
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Enantioselective synthesis of (-)-cis-clavicipitic acid.
Journal of Organic Chemistry, 2007Co-Authors: Jin-mo Ku, Byeong-seon Jeong, Hyeung-geun ParkAbstract:An enantioselective synthetic method for (−)-cis-clavicipitic acid (1) was reported. 1 was obtained in 10 steps (99% ee and 20% overall yield) from 1H-indole-3-carboxylic acid methyl ester (9) via asymmetric phase-transfer Catalytic Alkylation and diastereoselective Pd(II)-catalyzed intramolecular aminocyclization as key steps.
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Total Synthesis of (+)-Hygrine via Asymmetric Phase-Transfer Catalytic Alkylation
Journal of Organic Chemistry, 2006Co-Authors: Byeong-seon Jeong, Jin-mo Ku, Hyeung-geun ParkAbstract:The first enantioselective synthesis of (+)-hygrine (1) is reported. 1 was obtained in 12 steps with 29% overall yield and 97% ee via asymmetric phase-transfer Catalytic Alkylation and ring-closing metathesis as key steps. The absolute configuration of (+)-hygrine could be directly confirmed as R.
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Enantioselective Synthetic Method for α-Alkylserine via Phase-Transfer Catalytic Alkylation of 2-Phenyl-2-oxazoline-4- carbonylcamphorsultam
Journal of Organic Chemistry, 2005Co-Authors: Myoung Joo Kang, Byeong-seon Jeong, Jin-mo Ku, Ji-yeon Choi, Hveung-geeun ParkAbstract:An enantioselective synthetic method for α-alkylserines by the phase-transfer Catalytic Alkylation of 2-phenyl-2-oxazoline-4-carbonylcamphorsultam (4a) was developed. The phase-transfer Catalytic α-Alkylation of 4a using P2-Et at −78 °C gave α-Alkylation (75∼99%, 90∼97% de), which could be easily hydrolyzed to α-alkylserines.