- Catalytic Staudinger Reduction at Room Temperature
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We report an efficient catalytic Staudinger reduction at room temperature that enables the preparation of a structurally diverse set of amines from azides in excellent yields. The reaction is based on the use of catalytic amounts of triphenylphosphine as a phosphine source and diphenyldisiloxane as a reducing agent. Our catalytic Staudinger reduction exhibits a high chemoselectivity, as exemplified by reduction of azides over other common functionalities, including nitriles, alkenes, alkynes, esters, and ketones.
- Lenstra, Danny C.,Wolf, Joris J.,Mecinovi?, Jasmin
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p. 6536 - 6545
(2019/05/24)
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- Sustainable organophosphorus-catalysed Staudinger reduction
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A highly efficient and sustainable catalytic Staudinger reduction for the conversion of organic azides to amines in excellent yields has been developed. The reaction displays excellent functional group tolerance to functionalities that are otherwise prone to reduction, such as sulfones, esters, amides, ketones, nitriles, alkenes, and benzyl ethers. The green nature of the reaction is exemplified by the use of PMHS, CPME, and a lack of column chromatography.
- Lenstra, Danny C.,Lenting, Peter E.,Mecinovi?, Jasmin
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supporting information
p. 4418 - 4422
(2018/10/17)
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- Asymmetric transfer hydrogenation of β,γ-alkynyl α-lmino esters by a bronsted acid
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Asymmetric synthesis of trans-alkenyl α-amino esters was realized by chiral phosphoric acid catalyzed transfer hydrogenatlon of β,γ- alkynyl α-imino esters. Utilizing Hantzsch esters as the hydrogen donor, both the alkyne and Imine moieties of β,γ-alkynyl
- Kang, Qiang,Zhao, Zhuo-An,You, Shu-Li
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scheme or table
p. 2031 - 2034
(2009/04/10)
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- Unprecedented effects of additives and ligand-to-metal ratio on the enantiofacial selection of copper-catalyzed alkynylation of a-imino ester with arylacetylenes
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The first catalytic asymmetric addition of arylacetylenes to α-imino esters was carried out using chiral copper(I) complexes as catalysts under mild reaction conditions, providing the corresponding alkynylation products in good yields with 67-74% ee value
- Shao, Zhihui,Wang, Jun,Ding, Kai,Chan, Albert S. C.
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p. 2375 - 2379
(2008/09/19)
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- Ethyl 2,4-dioxo-4-phenylbutyrate: A versatile intermediate for the large-scale preparation of enantiomerically pure α-hydroxy and α-amino acid esters
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Starting from ethyl 2,4-dioxo-4-phenylbutyrate, both enantiomers of six enantiomerically pure α-hydroxy and α-amino acid esters (homophenylalanine derivatives) were prepared on >100 g scale. The key step involves a Pt-cinchona catalyzed enantioselective hydrogenation followed by enrichment via crystallization. All derivatives are commercially available.
- Blaser, Hans-Ulrich,Burkhardt, Stephan,Kirner, Hans Juerg,Moessner, Tanja,Studer, Martin
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p. 1679 - 1682
(2007/10/03)
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- Reduction of azides to amines or amides with zinc and ammonium chloride as reducing agent
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Alkyl azides and acyl azides were reduced to the corresponding amines and amides with zinc and ammonium chloride as reducing agent under mild conditions in good to excellent yield.
- Lin, Wenqing,Zhang, Xiaomei,He, Ze,Jin, Yi,Gong, Liuzhu,Mi, Aiqiao
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p. 3279 - 3284
(2007/10/03)
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- Amino Acid Anhydride Hydrochlorides as Acylating Agents in Friedel-Crafts Reaction: A Practical Synthesis of L-Homophenylalanine
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The use of amino acid hydrochlorides as acylating agents in Friedel-Crafts reaction is presented for the first time. A practical and convenient route to L-homophenylalanine from L-aspartic acid in 3 steps in 80 percent overall yield with >99 percent ee is thus achieved.
- Lin, Wenqing,He, Ze,Zhang, Haile,Zhang, Xiaomei,Mi, Aiqiao,Jiang, Yaozhong
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p. 1007 - 1009
(2007/10/03)
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- Studies on Angiotensin Converting Enzyme Inhibitors. 4. Synthesis and Angiotensin Converting Enzyme Inhibitory Activities of 3-Acyl-1-alkyl-2-oxoimidazolidine-4-carboxylic Acid Derivatives
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(4S)-1-Alkyl-3-acyl>-2-oxoimidazolidine-4-carboxylic acid derivatives (3) were prepared by two methods.Their angiotensin converting enzyme (ACE) inhibitory activities and antihypertensive effects were evaluated, and the structure-activity relationships were discussed.The dicarboxylic acids 3a-n possessing S,S,S configuration showed potent in vitro ACE inhibitory activities with IC 50 values of 1.1x10-8-1.5x10-9 M.The most potent compound in this series, monoester 3p, had an ID 50 value of 0.24 mg/kg, po for inhibition of angiotensin I induced pressor response in normotensive rats and produced a dose-dependent decrease in systolic blood pressure of spontaneously hypertensive rats (SHRs) at doses of 1-10 mg/kg, po.
- Hayashi, Kimiaki,Nunami, Ken-ichi,Kato, Jyoji,Yoneda, Naoto,Kubo, Masami,et al.
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p. 289 - 297
(2007/10/02)
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- Novel sulfonic acid esters and their preparation
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The invention relates to novel sulfonic acid esters of formula I STR1 wherein R 1 is C 5 -C 6 cycloalkyl which is unsubstituted or substituted by C 1 -C 7 alkyl, unsubstituted or substituted phenyl, R 2 is C 1 -C 7 alkyl, R 3 is phenyl which is substituted by halogen or nitro, and the asterisk denotes a carbon atom that is either present in the preponderant number of molecules in the S configuration or in the preponderant number of molecules in the R configuration.These compounds can be prepared by enantio-selective reduction of 4--R 1 --substituted α-oxobutyric acid compounds and subsequent conversion of the resultant α-hydroxy group into the --OSO 2 --R 3 group. The compounds of formula I are suitable intermediates for the preparation of ACE inhibitors or precursors thereof.
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- Synthesis and Pharmacology of the Potent Angiotensin-Converting Enzyme Inhibitor N--(S)-alanyl-(S)-pyroglutamic Acid
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Structure 3a, a potent angiotensin-converting enzyme inhibitor, was prepared in five steps from L-(+)-α-amino-4-phenylbutyric acid by construction of the activated side-chain ester 16, displacement with L-pyroglutamate ester anion, and deblocking.Diastereomer separation was accomplished by chromatography at the diester stage, 17.Pharmacological assays established that 3a parallels enalapril in its ability to inhibit converting enzyme and lower blood pressure.
- Johnson, Alexander L.,Price, William A.,Wong, Pancras C.,Vavala, Robert F.,Stump, John M.
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p. 1596 - 1602
(2007/10/02)
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- Process for preparing antihypertensive 1-substituted cyclic lactam-2-carboxylic acids and their derivatives
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Certain antihypertensive 1-substituted cyclic lactam-2-carboxylic acids and their derivatives are prepared by reacting an ester of the formula STR1 with a suitable derivative of the formula STR2
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