- Electrochemical Dimethyl Sulfide-Mediated Esterification of Amino Acids
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Dimethyl sulfide-mediated electrochemical synthetic strategy for esterification of amino acids has been reported. A series of amino acids could react smoothly with alcohols, affording the desired esterification products with good efficiency. Importantly, the tolerance of peptides and gram-scale synthesis shed light on the utility of this protocol. Mechanistically, the dimethyl sulfide as a mediator plays an essential role in the transformation of amino acids.
- Li, Yongli,Wang, Huamin,Zhang, Heng,Lei, Aiwen
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supporting information
p. 3023 - 3028
(2021/08/30)
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- Scandium(III) triflate-promoted serine/threonine-selective peptide bond cleavage
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The site-selective cleavage of peptide bonds is an important chemical modification that is useful not only for the structural determination of peptides, but also as an artificial modulator of peptide/protein function and properties. Here we report site-selective hydrolysis of peptide bonds at the Ser and Thr positions with a high conversion yield. This chemical cleavage relies on Sc(iii)-promoted N,O-acyl rearrangement and subsequent hydrolysis. The method is applicable to a broad scope of polypeptides with various functional groups, including a post-translationally modified peptide that is unsuitable for enzymatic hydrolysis. The system was further extended to site-selective cleavage of a native protein, Aβ1-42, which is closely related to the onset of Alzheimer's disease.
- Ni, Jizhi,Sohma, Youhei,Kanai, Motomu
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supporting information
p. 3311 - 3314
(2017/03/22)
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- Enantioselective synthesis of anti-β-hydroxy-α-amido esters by asymmetric transfer hydrogenation in emulsions
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Herein, we present two methods for an asymmetric transfer hydrogenation through the dynamic kinetic resolution of α-amido-β-ketoesters. These procedures yield the corresponding anti-β-hydroxy-α-amido esters in good yields and with good diastereo- and enantioselectivities. First, the scope of the reduction of α-amido-β-ketoesters by using triethylammonium formate azeotrope is examined. Then, an emulsion technology with sodium formate is explored, which allows for broader substrate scope, faster reaction times, and lower catalyst loading. Furthermore, these reactions are operationally simple and can be set up in air.
- Seashore-Ludlow, Brinton,Villo, Piret,Somfai, Peter
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supporting information; experimental part
p. 7219 - 7223
(2012/07/13)
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- On the reactivity of imidazole carbamates and ureas and their use as esterification and amidation reagents
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The optimization, substrate scope, and mechanism of esterification and amidation of carboxylic acids mediated by imidazole-based reagents are discussed. The innate reactivity of carbonylimidazole reagents with a range of nucleophiles is also explored. New reagents developed for the synthesis of α,β-unsaturated esters are described, as are reagents for the preparation of tertiary amides directly from carboxylic acids.
- Heller, Stephen T.,Sarpong, Richmond
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experimental part
p. 8851 - 8859
(2011/12/02)
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- Palladium-catalysed enantioselective α-hydroxylation of β-ketoesters
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Highly enantioselective α-hydroxylation of cyclic and acyclic 1,3-ketoesters can be achieved with up to 98% ee using a dicationic palladium(ii) catalyst and dimethyldioxirane as oxidant.
- Smith, Alexander M.R.,Billen, Denis,Hii, King Kuok
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supporting information; experimental part
p. 3925 - 3927
(2010/01/06)
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- PYRIMIDINE HYDRAZIDE COMPOUNDS AS PGDS INHIBITORS
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This invention is directed to a compound wherein R1, R2, R3, R4 and L1 are as defined herein, a pharmaceutical composition comprising the compound, and the use of the compound to treat allergic and/or
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Page/Page column 70
(2008/12/04)
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- Novel inhibitor compounds specific of secreted non-pancreatic human a2phospholipase of group II
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The present invention relates to a compound of the following formula (I) and pharmaceutical compositions containing the compound of formula (I): wherein D, Y, A, B, p, q, W and R have the same meanings as defined in the specification.
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Page/Page column 10
(2010/02/11)
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- A facile new method for selective deprotection of N- (tertbutoxycarbonyl)-protected carboxamides with Yb(OTf)3 supported on silica gel
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A selective new method for the deprotection of N-Boc carboxamides was achieved by using Yb(OTf)3 supported on silica gel trader solvent-free conditions.
- Kotsuki, Hiyoshizo,Ohishi, Takeshi,Araki, Tomohiro,Arimura, Koji
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p. 4869 - 4870
(2007/10/03)
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- New facile alkoxycarbonylating agent, alkyl pyrazole-1-carboxylates. The preparation and the utilities
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Alkyl pyrazole-1-carboxylates (2), which were readily prepared from alkyl chloroformate or carbazate in good yields, were provided as the new facile alkoxycarbonylating agents toward the Grignard reagents for the synthesis of one carbon higher carboxylic esters. Also amines were alkoxycarbonylated by 2 to produce the corresponding urethanes even in an aqueous medium. Benzyl 3,5-dimethylpyrazole-1-carboxylate (2d) could be utilized for the Cbz-protection of amino acids and esters in good yield without any racemization.
- Kashima, Choji,Tsuruoka, Shiro,Mizuhara, Saori
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p. 14679 - 14688
(2007/10/03)
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- Papain-catalyzed esterification of N(α)-protected amino acids and dipeptides with ethanol in different organic systems
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The papain-catalyzed esterification of N(α)-protected amino acids and dipeptides with ethanol in mostly hydrophobic organic solvent systems containing low amounts of water has been investigated. The influence of various parameters, such as the amount of added water, reaction time, temperature and pH of added buffer, on the yield of ester was studied first on the model substrate Z-Ala. The optimized reaction conditions were then used for esterification of a series of N(α)-protected amino acids and dipeptides.
- Braun,Kuhl
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p. 203 - 206
(2007/10/03)
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- A Total Synthesis of Horsfiline via Aryl Radical Cyclisation
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Cyclisation of 15 via the derived aryl radical leads to spiropyrrolidinyl-oxindole 16, which is converted in three steps into the oxindole alkaloid horsfiline 3.
- Jones, Keith,Wilkinson, James
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p. 1767 - 1769
(2007/10/02)
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- A novel and versatile route to mixed p-toluenesulphonic carboxylic anhydrides
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A versatile route to the mixed p-toluenesulphonic carboxylic anhydrides (1) via the reaction of tetra-n-butylammonium carboxylate (2) with p-toluenesulphonyl chloride in a neutral medium is described.Some of the synthetic applications of the proposed method are described.
- Kumar, Arvind,Srivastava, Nivedita,Mital, Alka
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p. 606 - 607
(2007/10/02)
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- Novel esterifying agents, and their production and use
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A process for esterifying organic carboxylic acids which comprises reacting an organic carboxylic acid with a carbonic acid ester of the formula: EQU1 wherein R is an organic group and X and Y are each a negative group in the presence of a basic substance to make esterified the carboxyl group in the organic carboxylic acid. The process is advantageous in affording the objective carboxylic ester in a good yield within a short time by a simple operation under a mild reaction condition.
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