On the active site for hydrolysis of aryl amides and choline esters by human cholinesterases
摘要:
Cholinesterases, in addition to their well-known esterase action, also show an aryl acylamidase (AAA) activity whereby they catalyze the hydrolysis of amides of certain aromatic amines. The biological function of this catalysis is not known. Furthermore, it is not known whether the esterase catalytic site is involved in the AAA activity of cholinesterases. It has been speculated that the AAA activity, especially that of butyrylcholinesterase (BuChE), may be important in the development of the nervous system and in pathological processes such as formation of neuritic plaques in Alzheimer's disease (AD). The substrate generally used to study the AAA activity of cholinesterases is N-(2-nitrophenyl)acetamide. However, use of this substrate requires high concentrations of enzyme and substrate, and prolonged periods of incubation at elevated temperature. As a consequence, difficulties in performing kinetic analysis of AAA activity associated with cholinesterases have hampered understanding this activity. Because of its potential biological importance, we sought to develop a more efficient and specific substrate for use in studying the AAA activity associated with BuChE, and for exploring the catalytic site for this hydrolysis. Here, we describe the structure-activity relationships for hydrolysis of anilides by cholinesterases. These studies led to a substrate, N-(2-nitrophenyl)trifluoroacetamide, that was hydrolyzed several orders of magnitude faster than N-(2-nitrophenyl)acetamide by cholinesterases. Also, larger N-(2-nitrophenyl)alkylamides were found to be more rapidly hydrolyzed by BuChE than N-(2-nitrophenyl)acetamide and, in addition, were more specific for hydrolysis by BuChE. Thus, N-(2-nitrophenyl)alkylamides with six to eight carbon atoms in the acyl group represent suitable specific substrates to investigate further the function of the AAA activity of BuChE. Based on the substrate structure-activity relationships and kinetic studies, the hydrolysis of anilides and esters of choline appears to utilize the same catalytic site in BuChE. (c) 2006 Elsevier Ltd. All rights reserved.
On the active site for hydrolysis of aryl amides and choline esters by human cholinesterases
摘要:
Cholinesterases, in addition to their well-known esterase action, also show an aryl acylamidase (AAA) activity whereby they catalyze the hydrolysis of amides of certain aromatic amines. The biological function of this catalysis is not known. Furthermore, it is not known whether the esterase catalytic site is involved in the AAA activity of cholinesterases. It has been speculated that the AAA activity, especially that of butyrylcholinesterase (BuChE), may be important in the development of the nervous system and in pathological processes such as formation of neuritic plaques in Alzheimer's disease (AD). The substrate generally used to study the AAA activity of cholinesterases is N-(2-nitrophenyl)acetamide. However, use of this substrate requires high concentrations of enzyme and substrate, and prolonged periods of incubation at elevated temperature. As a consequence, difficulties in performing kinetic analysis of AAA activity associated with cholinesterases have hampered understanding this activity. Because of its potential biological importance, we sought to develop a more efficient and specific substrate for use in studying the AAA activity associated with BuChE, and for exploring the catalytic site for this hydrolysis. Here, we describe the structure-activity relationships for hydrolysis of anilides by cholinesterases. These studies led to a substrate, N-(2-nitrophenyl)trifluoroacetamide, that was hydrolyzed several orders of magnitude faster than N-(2-nitrophenyl)acetamide by cholinesterases. Also, larger N-(2-nitrophenyl)alkylamides were found to be more rapidly hydrolyzed by BuChE than N-(2-nitrophenyl)acetamide and, in addition, were more specific for hydrolysis by BuChE. Thus, N-(2-nitrophenyl)alkylamides with six to eight carbon atoms in the acyl group represent suitable specific substrates to investigate further the function of the AAA activity of BuChE. Based on the substrate structure-activity relationships and kinetic studies, the hydrolysis of anilides and esters of choline appears to utilize the same catalytic site in BuChE. (c) 2006 Elsevier Ltd. All rights reserved.
Trifluoroacetylation of amines with trifluoroacetic acid in the presence of trichloroacetonitrile and triphenylphosphine
作者:Joong-Gon Kim、Doo Ok Jang
DOI:10.1016/j.tetlet.2009.11.105
日期:2010.1
We developed a mild and convenient trifluoroacetylation process for amines using a combination of trichloroacetonitrile and triphenylphosphine. The reaction that we designed is applicable to the trifluoroacetylation of a wide variety of amines, including amines with stereogenic centers, which underwent trifluoroacetylation without racemization.
A one-pot procedure for trifluoroacetylation of arylamines using trifluoroacetic acid as a trifluoroacetylating reagent
作者:Junpei Ohtaka、Takeshi Sakamoto、Yasuo Kikugawa
DOI:10.1016/j.tetlet.2009.01.088
日期:2009.4
procedure for the preparation of aryl trifluoroacetamides from aryl amines is described that employs 2–4 M equiv of trifluoroacetic acid in refluxing xylene as a trifluoroacetylating agent. Addition of an amount of pyridine that is equimolar to the amount of trifluoroacetic acid present in the reaction mixture facilitates the trifluoroacetylation of rather basic arylamines.
P
<sup>III</sup>
/P
<sup>V</sup>
=O Catalyzed Cascade Synthesis of N‐Functionalized Azaheterocycles
作者:Trevor V. Nykaza、Gen Li、Junyu Yang、Michael R. Luzung、Alexander T. Radosevich
DOI:10.1002/anie.201914851
日期:2020.3.9
the modular synthesis of diverse N-aryl and N-alkyl azaheterocycles (indoles, oxindoles, benzimidazoles, and quinoxalinediones) is reported. The method employs a small-ring organophosphorus-based catalyst (1,2,2,3,4,4-hexamethylphosphetane P-oxide) and a hydrosilane reductant to drive the conversion of ortho-functionalized nitroarenes into azaheterocycles through sequential intermolecular reductive C-N
A short synthesis of phenanthro[2,3- d ]imidazoles from dehydroabietic acid. Application of the methodology as a convenient route to benzimidazoles
作者:Tatiana Fonseca、Bárbara Gigante、Thomas L Gilchrist
DOI:10.1016/s0040-4020(00)01158-3
日期:2001.2
Methyl cis-deisopropyldehydroabietate was selectively nitrated at the 12-position by reaction with ‘claycop’, a montmorillonite clay impregnated with copper(II) nitrate. The 12-nitro compound was reduced to the corresponding amine and this was subjected to a combined acylation and ortho nitration. The compounds so produced were further converted into octahydro-1H-phenanthro[2,3-d]imidazoles by reductive
通过与“ claycop”(一种浸有硝酸铜(II)的蒙脱土)反应,在12位选择性地将顺式-异异丙基脱氢松香酸甲酯硝化。将12-硝基化合物还原为相应的胺,并将其进行酰化和邻硝化的组合。通过还原环化将如此产生的化合物进一步转化为八氢-1 H-菲并[2,3- d ]咪唑。结果表明,相同的酰化-邻硝化方法可从苯胺短时间合成2-取代的苯并咪唑。
Glycosylation with ulosonates under Mitsunobu conditions: scope and limitations
A systematic study was performed by using Mitsunobuconditions (diethyl azodicarboxylate, Ph3P or n-Bu3P in THF or CH3CN) for glycosylations with methyl 3,4,5,7-tetra-O-benzoyl-α-D-gluco-hept-2-ulopyranosonate. From a set of 47 O-, N-, S- and C-nucleophiles, phenols and N-hydroxy compounds with a pKa of 5–8, phthalimide, benzotriazole, 6-chloropurine, an oxazolidinedione and several tetrazoles with
通过使用Mitsunobu条件(在THF或CH 3 CN中的偶氮二羧酸二乙酯,Ph 3 P或n -Bu 3 P )进行甲基,3,4,5,7-四-O-苯甲酰基-α- D的糖基化研究-葡萄糖-庚-2- ulopyranosonate。选自47种O-,N-,S-和C-亲核试剂,酚和N-羟基化合物,其ap K a为5-8,邻苯二甲酰亚胺,苯并三唑,6-氯嘌呤,恶唑烷二酮和若干具有ap K a的四唑苯酚的比例为4-8,而苯酚以中等到非常高的产率提供了相应的产物,而C-亲核试剂则没有反应性。对三卤代乙酰苯胺进行O-糖基化反应,得到O-糖基-N-芳基三卤代乙酰亚胺酸酯,这是常规的O-亚氨基化无法制备的。所有反应都是高度立体选择性的,仅产生β(D)异构体。用甲基(5-乙酰氨基-4,7,8,9-四- ø -乙酰基-3,5-二脱氧d -甘油基- d -半乳-2-壬基吡喃二酮酸)酚和苯并三唑生成了预期的产物,但