2440-79-1Relevant articles and documents
Concentration- and Structure-Dependent Effects of Amides on Protease Activity in Organic Solvents
Yamamoto, Yasuhito,Kise, Hideo
, p. 1367 - 1370 (1994)
The catalytic activity of α-chymotrypsin (CT) in the transesterification of N-acetyl-L-tyrosine methyl ester to its ethyl ester in aqueous-organic media was markedly enhanced by replacing a part of water with foramide.The activity of CT was strongly dependent on the formamide/water ratio, and excess formamide retarded the activity.Addition of formamide to reaction mixtures at constant water contents exhibited similar activation-deactivation profiles for CT.A kinetic study revealed that the rate acceleration is due to an increase in kcat rather than a change in Km.At a given concentration of amides (0.5 M, M = mol dm-3), propionamide and DMF were much less effective than formamide for activation of CT.The results suggest that foramide interacts with CT in a different way from water.
Effects of metal salts on the structure and activity of α-chymotrypsin in ethanol/water
Sasaki, Toshiya,Kise, Hideo
, p. 1321 - 1325 (1999)
The catalytic activity and circular dichroic (CD) spectra of α- chymotrypsin (CT) were measured in ethanol/water (95/5, v/v) solution containing small amounts of metal salts. Although the catalytic activity of CT increased upon the addition of all the metal salts used, the magnitude of activity increase was different for different metal salts. Especially, calcium acetate accelerated the transesterification of amino acid up to 6 fold at 100 μM. The secondary and tertiary structures of CT were also changed by metal salts, as studied by CD measurements. The effects of metal salts on the stability of CT in ethanol/water were also studied, and it was found that the residual activity of CT after 7 days in ethanol/water in the presence of Ca(OCOCH3)2 was about 20% of the initial activity. The change in activity was closely correlated with the change in the mean residue ellipticity of CT at 208 or 230 nm.
Increase of catalytic activity of alpha-chymotrypsin by metal salts for transesterification of an amino acid ester in ethanol.
Sasaki,Kise
, p. 1196 - 1197 (1997)
alpha-Chymotrypsin-catalyzed transesterification of N-acetyl-L-tyrosine methyl ester in ethanol was markedly accelerated by addition of small amounts of divalent metal salts. The reaction rate dependent not only on the nature of metal ions but also on the nature of anionic counter ions. Calcium acetate was the most effective among the metal salts used. The reaction followed Michaelis-Menten kinetics, and it was found that the reaction increase is due to the increase in kcat.
A Metal-Free Direct Arene C?H Amination
Wang, Tao,Hoffmann, Marvin,Dreuw, Andreas,Hasagi?, Edina,Hu, Chao,Stein, Philipp M.,Witzel, Sina,Shi, Hongwei,Yang, Yangyang,Rudolph, Matthias,Stuck, Fabian,Rominger, Frank,Kerscher, Marion,Comba, Peter,Hashmi, A. Stephen K.
supporting information, p. 2783 - 2795 (2021/04/05)
The synthesis of aryl amines via the formation of a C?N bond is an essential tool for the preparation of functional materials, active pharmaceutical ingredients and bioactive products. Usually, this chemical connection is only possible by transition metal-catalyzed reactions, photochemistry or electrochemistry. Here, we report a metal-free arene C?H amination using hydroxylamine derivatives under benign conditions. A charge transfer interaction between the aminating reagents TsONHR and the arene substrates enables the chemoselective amination of the arene, even in the presence of various functional groups. Oxygen was crucial for an effective conversion and its accelerating role for the electron transfer step was proven experimentally. In addition, this was rationalized by a theoretical study which indicated the involvement of a dioxygen-bridged complex with a “Sandwich-like” arrangement of the aromatic starting materials and the aminating agents at the dioxygen molecule. (Figure presented.).
Preparation method of rosastat key intermediate
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, (2020/09/09)
The invention provides a preparation method of a rosastat key intermediate. The intermediate I is 4-hydroxy-1-methyl-7-phenoxy isoquinoline-3-carboxylic ester. The preparation method comprises the following steps: with tyrosine as an initial raw material, sequentially carrying out esterification, acylation, etherification, cyclization, aromatization and oxidation rearrangement reaction to preparethe rosastat key intermediate. The preparation method has the advantages of cheap and easily available raw materials, environmental protection, avoiding of use of phosphorus oxychloride, polyphosphoric acid and other environmentally unfriendly reagents in the cyclization reaction, simple process, simple operation and mild reaction conditions; and the method has the advantages of less three wastesand higher product yield and purity, and is suitable for industrial production.