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Nucleophilic groups

The amino acids serine and cysteine are common inhabitants of active sites. These amino acids have nucleophilic residues (OH and SH respectively) which are able to participate in the reaction mechanism. They do this by reacting with the substrate to form intermediates which would not be formed in the uncatalysed reaction. These intermediates offer an alternative reaction pathway which may avoid a high-energy transition state and hence increase the rate of the reaction. [Pg.39]

Normally, an alcoholic group such as that on serine is not a good nucleophile. However, there is usually a histidine residue close by to catalyse the reaction. For example, the mechanism by which chymotrypsin hydrolyses peptide bonds is shown in Fig. 4.20. [Pg.39]

The presence of a nucleophilic serine residue means that water is not required in the initial stages of the mechanism. This is important since water is a poor nucleophile and may also find it difficult to penetrate a hydrophobic active site. Secondly, a water molecule would have to drift into the active site, and search out the carboxyl group before it could attack it. This would be something similar to a game of blind man s buff. The enzyme, on the other hand, can provide a serine OH group, positioned in exactly the right spot to react with the substrate. Therefore, the nucleophile has no need to search for its substrate. The substrate has been delivered to it. [Pg.39]

Water is required eventually to hydrolyse the acyl group attached to the serine residue. However, this is a much easier step than the hydrolysis of a peptide link since esters are more reactive than amides. Furthermore, the hydrolysis of the peptide link means that one half of the peptide can drift away from the active site and leave room for a water molecule to enter. [Pg.40]

As far as the medicinal chemist is concerned, an understanding of the mechanism can help in the design of more powerful inhibitors. [Pg.40]


Monochloroacetamides are cleaved (by assisted removal ) by reagents that contain two nucleophilic groups (e.g., o-phenylenediamine, thiourea, 1-piperi-dinethiocarboxamide, 3-nitropyridine-2-thione, 2-aminothiophenol ) ... [Pg.352]

Several chemical compounds may cause inflammation or constriction of the blood vessel wall (vasoconstriction). Ergot alkaloids at high doses cause constriction and thickening of the vessel wall. Allylamine may also induce constriction of coronary arteries, thickening of their smooth muscle walls, and a disease state that corresponds to coronary heart disease. The culprit is a toxic reactive metabolite of allylamine, acrolein, that binds covalently to nucleophilic groups of proteins and nucleic acids in the cardiac myocytes. [Pg.297]

The substitution of fairly labile nucleophilic groups (halogen, methoxy group) in the 3- and 5-positions, and the noncatalytic substitution of the diazonium group at C-4, are to be considered as nucleophilic substitution reactions. As in the benzenoid series, these reactions are believed to proceed in the former case by the Sx2 mechanism and in the latter by the SnI mechanism. [Pg.390]

An artificial metalloenzyme (26) was designed by Breslow et al. 24). It was the first example of a complete artificial enzyme, having a substrate binding cyclodextrin cavity and a Ni2+ ion-chelated nucleophilic group for catalysis. Metalloenzyme (26) behaves a real catalyst, exhibiting turnover, and enhances the rate of hydrolysis of p-nitrophenyl acetate more than 103 fold. The catalytic group of 26 is a -Ni2+ complex which itself is active toward the substrate 1, but not toward such a substrate having no metal ion affinity at a low catalyst concentration. It is appearent that the metal ion in 26 activates the oximate anion by chelation, but not the substrate directly as believed in carboxypeptidase. [Pg.153]

The processes of complex-ion formation referred to above can be described by the general term complexation. A complexation reaction with a metal ion involves the replacement of one or more of the coordinated solvent molecules by other nucleophilic groups. The groups bound to the central ion are called ligands and in aqueous solution the reaction can be represented by the equation ... [Pg.51]

Substitution reactions where the nucleophilic group was a single free hydroxyl group of a saccharide, the other ones being protected, were also studied. The expected ether-amides or glycoside-amides were obtained from... [Pg.162]

Regardless of the way in which polydichlorophosphazene is prepared (vide supra), this polymer should be handled almost immediately because of the extreme reactivity of the chlorine atoms attached to the phosphorus of the poly-phosphazene chain toward nucleophilic groups and water. [Pg.178]

The most convenient route for introducing organo-ligands which do not contain strongly nucleophilic groups (e.g., -SH or -NH2), is from the organic halide (Section l,a, below) in most cases -SH and -NHj groups... [Pg.384]

Cyclic structures can form as a result of side reactions. One of the most common examples is the formation of diketopiperazines during the coupling of the third amino acid onto the peptide chain (Fig. 7). Intramolecular amide bond formation gives rise to a cyclic dipeptide of a six-membered ring structure, causing losses to the sequence and regeneration of the hydroxyl sites on the resin. The nucleophilic group on the resin can lead to fiuther unwanted reactions [14]. [Pg.36]

The displacement is effected preferentially by a nucleophilic group already in the molecule. Thus, in the above reaction there is no evidence that OTs- is displaced by the external ion, OMe-, under the conditions used, nor is there ahy displacement of OTs- of a sugar sulfonate by OAc-, Buch as was found to occur when the sulfonate of a monohydric aliphatic alcohol was treated with potassium acetate.11... [Pg.59]


See other pages where Nucleophilic groups is mentioned: [Pg.110]    [Pg.87]    [Pg.266]    [Pg.34]    [Pg.488]    [Pg.268]    [Pg.248]    [Pg.189]    [Pg.154]    [Pg.161]    [Pg.135]    [Pg.162]    [Pg.225]    [Pg.698]    [Pg.368]    [Pg.314]    [Pg.698]    [Pg.254]    [Pg.311]    [Pg.319]    [Pg.1176]    [Pg.358]    [Pg.137]    [Pg.86]    [Pg.220]    [Pg.62]    [Pg.259]    [Pg.128]    [Pg.59]    [Pg.238]    [Pg.238]    [Pg.307]    [Pg.104]    [Pg.205]    [Pg.59]    [Pg.60]    [Pg.80]    [Pg.179]    [Pg.43]    [Pg.176]   
See also in sourсe #XX -- [ Pg.20 , Pg.21 , Pg.29 , Pg.35 ]




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ALDEHYDES AND KETONES NUCLEOPHILIC ADDITION TO THE CARBONYL GROUP

Acyl group nucleophilic substitution

Acylation hydroxyl groups nucleophilic

Acylation of Nucleophilic Oxygen and Nitrogen Groups

Addition of Carbon Nucleophiles to Carbonyl Groups

Alcohols with Additional Nucleophilic Groups

Alkoxy groups, nucleophilic displacement

Alkyl groups steric hindrance to nucleophilic substitution

Alkyl groups, nucleophilic attack

Alkylation hydroxyl groups nucleophilic

Amines with Additional Nucleophilic Groups

Aryl groups, nucleophilic attack

By nucleophilic attack onto carbonyl groups

Carbohydrates hydroxyl group nucleophilicity

Carbonyl group nucleophilic addition

Carbonyl group nucleophilic addition reactions

Carbonyl group nucleophilic attack

Carbonyl group nucleophilicity

Carbonyl group, nucleophilic addition cyclization

Carboxyl groups, electronic effects by cationic nucleophiles

Coupling nucleophiles, carboxylic groups

Deacylation hydroxyl groups nucleophilic

Displacement reactions, nucleophilic on 5 -methylene group of ATP

Displacement reactions, nucleophilic on carbonyl groups

Effects of Solvent, Leaving Group, and Nucleophile on Unimolecular Substitution

Electron withdrawing groups aromatic fluonne by nucleophiles

Electron-withdrawing groups nucleophilic additions, carbanion intermediates

Electron-withdrawing groups nucleophilic substitution

Electron-withdrawing groups, effect nucleophilic substitutions

Enantiotopic leaving group, nucleophilic substitution

Enzymes nucleophilic groups

Fibre-reactive Groups Reacting by Nucleophilic Addition

Fibre-reactive Groups Reacting by Nucleophilic Substitution

Functional Group Interconversion by Nucleophilic Substitution

Functional Group Transformation by Nucleophilic Substitution Reactions

Functional Groups by Nucleophilic Substitution at Saturated Carbon

Functional group nucleophilic

Functional groups transformation, by nucleophilic

Functional groups transformation, by nucleophilic substitution

Group 14 atoms nucleophilic substitution, intramolecular

Group 15 Nucleophiles. Nitrogen

Group 16 Nucleophiles. Oxygen

Group 16 atoms, nucleophilic substitution

Group 16 atoms, nucleophilic substitution alkene-alcohol reactions

Group 16 atoms, nucleophilic substitution proposed mechanism

Group 16 atoms, nucleophilic substitution recent studies

Group nucleophilic Fukui function

Group transfer, nucleophilic

Hydroxyl group nucleophilicity

Leaving group in nucleophilic aromatic substitutio

Leaving group, in nucleophilic

Leaving groups compared with nucleophiles

Leaving groups for nucleophilic

Leaving groups in aliphatic nucleophilic

Leaving groups in aromatic nucleophilic

Leaving groups in nucleophilic aromatic substitution

Leaving groups in nucleophilic substitution

Leaving groups in nucleophilic substitution reactions

Leaving groups nucleophilic substitution, asymmetric allylation

Leaving groups, reactivity in nucleophilic

Leaving groups, reactivity in nucleophilic aromatic substitution

Leaving-group effects in nucleophilic substitution

Metal groups nucleophilic substitution

Methyl group nucleophilic attack

Methylthio groups, nucleophilic substitution

Neighboring group effect, nucleophilic substitutions

Neighbouring-group in nucleophilic aliphatic

Nitro group in nucleophilic aromatic substitutio

Nitro groups nucleophilic addition, substitution

Nucleophile functional group

Nucleophile functional group Subject

Nucleophile substitution, neighboring group

Nucleophile to carbonyl groups

Nucleophiles Derived from Group 15 N, P, As, and Sb

Nucleophiles Derived from Group 16 O, S, Se, and Te

Nucleophiles addition to carbonyl groups

Nucleophiles and Leaving Groups

Nucleophiles and leaving groups compared

Nucleophiles and leaving groups reversible addition reactions

Nucleophiles and the leaving group

Nucleophiles from Group 14 C and Sn

Nucleophiles groups

Nucleophiles groups

Nucleophiles, electrophiles, and leaving groups

Nucleophiles, reactions with carbonyl group

Nucleophilic Addition of Allylic Groups from Boron Compounds

Nucleophilic Addition to Carbonyl Groups An Overview

Nucleophilic Attack on a Carbonyl Group

Nucleophilic Attack on a Temporarily Formed Imino Group

Nucleophilic Reactions of OH Groups

Nucleophilic Substitution with Displacement of Good Leaving Groups

Nucleophilic acyl substitution reactions leaving groups

Nucleophilic addition leaving-group effects

Nucleophilic addition to carbonyl groups

Nucleophilic addition to carbonyl groups aldehydes and ketones

Nucleophilic addition to the carbonyl group

Nucleophilic additions groups

Nucleophilic aliphatic leaving-group effects

Nucleophilic aromatic nitro-group displacement

Nucleophilic aromatic substitution activating groups, effects

Nucleophilic aromatic substitution leaving groups

Nucleophilic aromatic substitution nitro-group activated

Nucleophilic aromatic substitution nitro-group displacement

Nucleophilic attack at the carbonyl group

Nucleophilic attack on carbonyl groups

Nucleophilic displacement, leaving group

Nucleophilic displacement, of leaving groups

Nucleophilic displacement, sulfonyloxy group

Nucleophilic group, definition

Nucleophilic groups formation

Nucleophilic groups ketone functionalization

Nucleophilic groups phase-transfer-catalyzed

Nucleophilic groups polymerizations

Nucleophilic imidazole ring groups

Nucleophilic on carbonyl group

Nucleophilic reactions of carbonyl groups

Nucleophilic substitution allyl-based protecting groups

Nucleophilic substitution at a carbonyl group

Nucleophilic substitution at the carbonyl group

Nucleophilic substitution group

Nucleophilic substitution leaving groups

Nucleophilic substitution nucleofugal groups

Nucleophilic substitution of other groups

Nucleophilic substitution on carbonyl groups carboxylic acid derivatives

Nucleophilic substitution reactions groups

Nucleophilic substitution reactions leaving groups

Nucleophilic substitution reactions, aliphatic leaving group effects

Nucleophilic substitution reactions, haloalkanes leaving group

Protecting Groups Cleaved by Nucleophilic Substitution

Protecting groups nucleophile properties

Protecting groups nucleophilic substitution

Protective Groups Cleavable by Nucleophiles or Other Reagents

Proteins nucleophilic groups

Reaction of Carbon Nucleophiles with Carbonyl Groups

Reaction of amino and imino groups with nucleophiles

Stereochemistry of nucleophilic addition at carbonyl groups

Substitution nucleophilic, leaving group effects

Sulfonyl groups, substitution nucleophilic

Sulfonyloxy group reaction with nucleophiles

Sulfur nucleophiles Group

Sulphinyl group nucleophilicity

Sulphonyl group nucleophilicity

The Reactions of Stable Nucleophilic Carbenes with Main Group

Thiocarbonyl group, nucleophilicity

Trends in Nucleophilicity Within a Group

Trialky lsilyl groups nucleophilic addition reactions

Trialkylsilyl groups nucleophilic addition reactions

Trichloromethyl groups, nucleophilic displacement

Triisopropylsilyl protecting groups nucleophilic addition reactions

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