- Facile and direct synthesis of symmetrical acid anhydrides using a newly prepared powerful and efficient mixed reagent
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An efficient mixed reagent for direct synthesis of symmetrical carboxylic anhydrides from carboxylic acids has been prepared. Carboxylic acids are converted to anhydrides using triphenylphosphine/ trichloroisocyanuric acid under mild reaction conditions at room temperature. Short reaction time, excellent yields of products, low cost, availability of reagents, simple experimental procedure, and easy work-up of the products are the main advantages of the presented method.
- Rouhi-Saadabad, Hamed,Akhlaghinia, Batool
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p. 479 - 485
(2015/01/30)
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- Syntheses of diacyltanshinol derivatives and their suppressive effects on macrophage foam cell formation by reducing oxidized LDL uptake
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A series of diacyltanshinol derivatives were synthesized by esterifying the corresponding o-hydroquinones of tanshinones. The suppressive effects of the synthesized compounds on oxidized low-density lipoprotein (oxLDL) uptake and oxLDL-induced macrophage-derived foam cell formation were evaluated. Our results indicated that the nicotinate derivatives 1a and 2a, modified from tanshinone IIA and cryptotanshinone, showed stronger suppressive activity on oxLDL uptake and the resultant foam cell formation relative to tanshinone IIA. Western Blot analysis indicated that derivatives 1a and 2a could dose-dependently inhibit the expression of oxLDL-induced LOX-1, implying that the suppressive effects of 1a and 2a on oxLDL uptake and foam cell formation could be at least partially attributed to the inhibition of LOX-1 expression in macrophages.
- Cheng, Xi,Zhang, Da-Li,Li, Xiao-Bing,Ye, Jian-Tao,Shi, Lei,Huang, Zhi-Shu,Gu, Lian-Quan,An, Lin-Kun
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- A versatile, practical, and inexpensive reagent, pyridine-3-carboxylic anhydride (3-PCA), for condensation reactions
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A highly useful method for the preparation of carboxylic esters and carboxamides from various carboxylic acids was established by using a novel condensing reagent, pyridine-3-carboxylic anhydride (3-PCA), in the presence of 4-(dimethylamino)pyridine as an activator. The reactions of various carboxylic acids with nucleophiles, such as alcohols or amines, afforded the corresponding carboxylic acids or carboxamides in good to high yields under mild conditions by using simple experimental procedure. In addition, it was confirmed that this protocol was applicable to a gram-scale synthesis and the by-products, including pyridine-3-carboxylic acid and pyridine-3-carboxylate (or pyridine-3- carboxamide) produced in situ, were easily removed by using a simple aqueous workup.
- Funasaka, Setsuo,Mukaiyama, Teruaki
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experimental part
p. 148 - 159
(2009/04/06)
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- Substrate activity screening: A fragment-based method for the rapid identification of nonpeptidic protease inhibitors
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A new fragment-based method for the rapid development of novel and distinct classes of nonpeptidic protease inhibitors, Substrate Activity Screening (SAS), is described. This method consists of three steps: (1) a library of N-acyl aminocoumarins with diverse, low molecular weight N-acyl groups is screened to identify protease substrates using a simple fluorescence-based assay, (2) the identified N-acyl aminocoumarin substrates are optimized by rapid analogue synthesis and evaluation, and (3) the optimized substrates are converted to inhibitors by direct replacement of the aminocoumarin with known mechanism-based pharmacophores. The SAS method was successfully applied to the cysteine protease cathepsin S, which is implicated in autoimmune diseases. Multiple distinct classes of nonpeptidic substrates were identified upon screening an N-acyl aminocoumarin library. Two of the nonpeptidic substrate classes were optimized to substrates with >8000-fold improvements in cleavage efficiency for each class. Select nonpeptidic substrates were then directly converted to low molecular weight, novel aldehyde inhibitors with nanomolar affinity to cathepsin S. This study demonstrates the unique characteristics and merits of this first substrate-based method for the rapid identification and optimization of weak fragments and provides the framework for the development of completely nonpeptidic inhibitors to many different proteases.
- Wood, Warren J. L.,Patterson, Andrew W.,Tsuruoka, Hiroyuki,Jain, Rishi K.,Ellman, Jonathan A.
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p. 15521 - 15527
(2007/10/03)
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