And amide hydrolysis

The most widely used homogeneous catalysts are simple acids and bases which catalyse well-known reactions such as ester and amide hydrolysis, and esterification. Such catalysts are inexpensive enough that they can be neutralized, easily separated fi om organic materials, and disposed of. This, of course, is not a good example of green chemistry and contributes to the huge quantity of aqueous salt waste generated by industry. 

In general, tetrazolium salts are stable in mineral acids. This stability has allowed a number of synthetic transformations such as ester and amide hydrolysis and demethylation of ethers etc.209-212 This is not the case with tetrazolium salts containing a heterocyclic substituent in the 3-position. They tend to decompose in mineral acid to the corresponding tetrazoles.230 Tetrazolyl-substituted tetrazoliums (146) and mesoionic tetrazoles, e.g., 145, are unaffected by acids.228,232... 

Many hydrolysis reactions, e.g. of esters and some amides, switch from an A2 mechanism to an A1 mechanism as the acidity is increased, and we will see several of these under the A2 reaction and amide hydrolysis headings. 

Phenylcarbamates, or carbanilates, generally exhibit low water solubilities, and thus they are almost immobile in soil systems. Chlorpropham and Propham are readily volatilized from soil systems, but Terbutol and Carbaryl (Fig. 10, Table 3) are not. Ester- and amide-hydrolysis, N-dealkylation and hydroxylation are among the chemical reactions that carbamates undergo. The N-methylcar-bamate insecticides (Fig. 10, Table 3) commonly used in soils are Carbaryl, Methiocarb,Aldicarb,and Carbofuran [74,173]. 

Before discussmg the mechanism of cleavage of carboxylic acid esters and amides by hydrolases, some chemical principles are worth recalling. The chemical hydrolysis of carboxylic acid derivatives can be catalyzed by acid or base, and, in both cases, the mechanisms involve addition-elimination via a tetrahedral intermediate. A general scheme of ester and amide hydrolysis is presented in Fig. 3. / the chemical mechanisms of ester hydrolysis will be... 

Metal-ion Catalysis of Ester and Amide Hydrolysi Carboxyl Group Catalysis Mechanistic Conclusions... 

Since serine-195 is the site of acylation, a good deal of recent work has been directed towards determining the efficiency of neighboring alcohol and phenol groups as intramolecular nucleophiles in ester and amide hydrolysis. In comparison with acetamide and butyramide, the hydrolysis of 7-hydroxybutyramide [equation (17)] in the alkaline and neutral pH-range is accelerated 800-fold (Bruice and Marquardt, 1962). These reactions are attack of alkoxide ion on the neutral and protonated amide function,... 

What is the explanation for the large effective molarity of a neighbouring alcohol function in ester and amide hydrolysis ... 

There are three fundamental questions concerning the mechanism of action of carboxypeptidase (1) How do metal ions affect ester and amide hydrolysis (2) Under what conditions will a neighbouring carboxyl group participate in ester and amide hydrolysis emd what is the mechanism of such participation (3) How will a metal ion affect... 

Major hydrolysis reactions are ester and amide hydrolysis. These are catalyzed by a group of enzymes with overlapping substrate specificity and activity. Hydrazides can also undergo hydrolysis. Some of the newer drugs such as hormones, growth factors, and cytokines now being produced are peptides, and certain toxins are also peptides or proteins, so the role of peptidases may be important. 

The optically active N-aminoindoline (265) has been applied to the asymmetric synthesis of a variety of a-amino acids (70JA2476, 2488). Starting from TV-benzoyl-1,2,3,4-tetrahy-droquinaldine (257), the chloro amide (258) was prepared by von Braun cleavage. Thermolysis converted (258) to the rrans-unsaturated amide (259) which was epoxidized. On base treatment the epoxide (260) underwent intramolecular nucleophilic displacement and amide hydrolysis to afford indoline (261) stereospecifically. Resolution of (261) was accomplished via the brucine salt of the N-o-carboxybenzoyl derivative (262). Alkaline hydrolysis, N-nitrosation and reduction yielded the levorotatory 1-aminoindoline (265). Reaction of... 

A different type of stereoelectronic control has been found in the breakdown in solution of tetrahedral addition intermediates that arise in ester and amide hydrolysis and other reactions of carboxyl and carbonyl groups. In the case of an intermediate such as structure 8.47, in which there are two atoms with non-bonded electrons (generally O or N), the lowest-energy transition state for breakdown is a conformation in which nonbonded electrons of each are anti to the group being expelled (structures 8.48).50... 

Introduction of RLi-unreactive silicon substituents has advantages in protection of Ar-C-H and Ar-CH3 sites. Thus taking advantage of the cooperativity of amide and methoxy DMG, metalation-silylation followed by metalation-E+ quench affords, after fluoride-mediated desilylation and amide hydrolysis, a route 1,2,5-substituted benzoic acids, 18 —> 19 (Scheme 5). Lateral metalation, of considerable utility in post-DoM chain extension [19], followed by double silyla-tion and further DoM-E+ quench and the same fluoride and acid treatment steps, furnishes 1,2,3,4-tetrasubstituted aromatic compounds, 20 —> 21 [10, 20],... 

Figure 6.9 Metal hydroxides in nitrile hydration (8 and 9) and amide hydrolysis (9 and 10).

Proteases Ester and amide hydrolysis, peptide synthesis... 

Reversible 02-Binding and Mechanistic Insights into Cu(I)/02-Mediated Arene Hydroxylation and Amide Hydrolysis... 

---