在四种季铵表面活性剂的胶束溶液中,已经研究了含组氨酸的三肽对氨基酸苯丙氨酸衍生的手性对硝基苯酯的裂解。酶样对映体选择性高达k I / k D观察到= 131(在0℃下)。通过假设在反应的过渡态下酯的I.对映异构体和三肽之间的疏水性驱动的稳定氢键可以使对映选择性合理化。与酯的D对映体反应中不存在该氢键。过渡态具有两极特性,并被胶束环境稳定。通过改变三肽的组成以及三肽和底物中N-保护基的长度,可以优化影响过渡态的反应物的亲水-疏水平衡。活性和对映选择性取决于季铵表面活性剂头基的结构。该头基的尺寸增加导致L酯的水解速率增加,并因此导致对映选择性增加。该作用归因于肽中存在的具有羧酸根基团的离子对形成程度的变化。与以前的研究相比,结果表明不需要手性表面活性剂即可获得高对映选择性。
METHOD FOR SYNTHESIZING 2-ALKYL-4-TRIFLUOROMETHYL-3-ALKYLSULFONYLBENZOIC ACIDS
申请人:Bayer CropScience Aktiengesellschaft
公开号:US20180305302A1
公开(公告)日:2018-10-25
A process for preparing 2-alkyl-4-trifluoromethyl-3-alkylsulfonylbenzoic acids of the formula (I) is described.
Here, the substituents are radicals such as alkyl and substituted phenyl.
The effect of micellar phase on the state and dynamics of some excited state charge transfer complexes
作者:B. Katusin-Razem、M. Wong、J. K. Thomas
DOI:10.1021/ja00474a007
日期:1978.3
different sites in micelles are also selected as e/sup -/ acceptors to investigate the effect of separation between P* and DMA on the forward and back e/sup -/ transfer processes. Similar studies were carried out with the molecule P-(CH/sub 2/)/sub 3/-DMA which forms intramolecular exciplexes. Here neither ion canmore » escape from the exciplex owing to the restraint of the propyl chain. The physical
METHOD FOR PRODUCING 3-ALKYLSULFANYL-2-CHLORO-N-(1-ALKYL-1H-TETRAZOL-5-YL)-4-TRIFLUOROMETHYL-BENZAMIDES
申请人:Bayer CropScience Aktiengesellschaft
公开号:US20190233382A1
公开(公告)日:2019-08-01
The invention relates to a method for producing 3-alkylsulfanyl-2-chloro-N-(1-alkyl-1H-tetrazol-5-yl)-4-trifluoromethyl-benzamides of formula (I). In said formula, the substituents R
1
and R
2
represent residues such as alkyl and substituted phenyl.
Fluorinated thermoset polyurethane elastomers prepared from polyether prepolymers formed mono-substituted fluorinated oxetane monomers
申请人:——
公开号:US20040087759A1
公开(公告)日:2004-05-06
This application is directed to novel fluorinated polymers and prepolymers derived from mono-substituted oxetane monomers having fluorinated alkoxymethylene side-chains and the method of making these compositions. The mono-substituted fluorinated oxetane monomers having fluorinated alkoxymethylene side-chains are prepared in high yield by the reaction of a fluorinated alkoxides with either 3-halomethyl-3-methyloxetane premonomers or aryl sulfonate derivative of 3-hydroxymethyl-3-methyloxetane premonomers. Preparation of a mono-substituted 3-bromomethyl-3-methyloxetane premonomer via a simple, high yield process amenable to commercial scaleup is also disclosed. The fluorinated oxetane monomers of this invention can be readily homo/co-polymerized in the presence of a Lewis acid and polyhydroxy compounds to obtain hydroxy-terminated polyether prepolymers having fluorinated alkoxymethylene side chains. Additionally, the fluorinated oxetane monomers can be copolymerized with non-fluorinated monomers such as tetrahydrofuran to give polyether prepolymers with improved hydrocarbon compatibility. These prepolymers are polydisperse and exhibit number average molecular weights from 5,000 to about 50,000. These prepolymers are amorphous oils with primary hydroxy end-groups and thus function efficiently as the soft block for the synthesis of a variety of thermoset/thermoplastic elastomers and plastics having the characteristics of very low surface energy, high hydrophobicity, low glasss transition temperature and low coefficient of friction. The polyurethanes derived from the prepolymers of this invention are elastomeric and, in addition to the above characteristics, exhibit high moisture resistance, high tear strength and excellent adhesion to a variety of substrates.
Amorphous polyether glycols based on bis-substituted oxetane monomers
申请人:Malik A. Aslam
公开号:US20060135729A1
公开(公告)日:2006-06-22
This invention is directed to mono- and bis-substituted oxetane monomers having fluorinated alkoxymethylene side chains, hydroxy-terminated prepolymers derived from these mono- and bis-substituted oxetane monomers and tetrahydrofuran (THF), and polymers produced from these prepolymers, as well as the synthesis processes associated with each, and the use of the monomers, prepolymers and ultimate polymers, both directly and as components of numerous compositions.