Hydrolysis of methyl ester

The TCBOC group is stable to the alkaline hydrolysis of methyl esters and to the acidic hydrolysis of r-butyl esters. It is rapidly cleaved by the supemucleophile lithium cobalt(I)phthalocyanine, by zinc in acetic acid, and by cobalt phthalocy-anine (0.1 eq., NaBH4, EtOH, 77-90% yield). 

The chloro atom of 2-[4-(6-chloronicotinoyl)benzyloxy]-3-methyl-4//-pyrido[l,2-n]pyrimidin-4-one, its 6-methyl derivative and 2-[4-(6-chlo-ronicotinoyl)benzylthio]-3-methyl-4//-pyrido[l,2-n]pyrimidin-4-one was replaced by a 4-piperidinopiperidino and 4-phenylpiperazino group with 4-piperidinopiperidine and 4-phenylpiperazine (96EUP733633). The carboxyl group of 2-[4-(4-carboxybenzoyl)benzyloxy]-3-methyl-4//-pyrido[l,2-n]pyrimidin-4-one, prepared by hydrolysis of methyl ester in DMF with 1 N NaOH, was reacted first with diethyl pyrocarbonate in DMF at room temperature and then with 4-phenylpiperazine and 4-piperidinopiperidine to give the appropriate amide derivatives (96EUP733633). 

For the delicate transesterification of a p-Lactam intermediate (for carbacephalosphorin skeleton), where originally hydrolysis of methyl ester was done homogeneously and then formation of the benzyl (or substituted benzyl) ester was done separately, Doecke et al. (1991) have devised a mild and efficient methodology using PTC. A dual use of a PT catalyst, Bu4NBr, in one pot was made in a CH2CI2 - H2O system. In the first step 5N NaOH was used, then the pH was adjusted to 7.2 to 7.8 and subsequently benzyl (or substituted benzyl) bromide was added. 

Neutralization Behavior after Hydrolysis of Methyl Esters [after Diehl (47)Y... 

By way of comparison, a very similar transformation has been accomplished without the use of the N-methoxy-A -methylamide. Hydrolysis of methyl ester (19) affords the corresponding carboxylic acid which was treated directly with methyllithium to afford a 70% overall yield of methyl ketone. ... 

Hopkinson, A.C. (1969). Unimolecular and Bimolecular Mechanisms in the Acid-catalyzed Hydrolysis of Methyl Esters of Aliphatic Monocarboxyilic Acids in Aqueous Sulphuric Add. 

Hydrolysis of methyl ester Hydrolysis of benzoate ester N-dealkylation... 

The alkaline hydrolysis of methyl esters of substituted benzoic acids has a Hammett p of 2.23. What would be the Bronsted 3 for the reaction when measured against the of the corresponding benzoic acid Comment on the magnitude of the effective charge at the reaction centre in the transition structure compared with that of the carboxylate anion product in the reference dissociation reaction ... 

Hopkinson, A.C. (1969) Unimolecular and bimolecular mechanisms in the acid-catalyzed hydrolysis of methyl esters of aliphatic monocarboxylic acids in aqueous sulphuric acid. J. Chem. Soc., B, 861-863. 

The dipeptide synthesis with free thermolysin (2 mg/ml) was carried out in water 10 mM of CLCa at pH 6,8 and 20 °C. The yield of peptide was below 10%, due to some reaction byproducts coming from the hydrolysis of methyl ester group of the peptide and consequent product hydrolysis as is shown in the following reactions ... 

Normally, one does not think of carbons as catalysts. However, carbons are sufficiently acidic or can be treated with nitric acid to be made acidic. These acidic carbons catalyze the hydrolysis of methyl esters. The carbons are more thermally robust than acidic sulfonic ion-exchange resins and can routinely operate at temperatures greater than 100°C. The nature of the acidic groups on... 

Example 3.3 The p value for alkaline hydrolysis of methyl esters of substituted benzoic acids is 2.38, and the rate constant for hydrolysis of methyl benzoate under the conditions of interest is 2 x 10 " s f Calculate the rate constant for the hydrolysis of methyl m-nitrobenzoate. 

Taft hypothesised that as the acid catalysed hydrolysis of methyl esters does not involve a change in overall charge between the ground state and the transition state, the reaction would be largely insensitive to the electronic nature of the substituent. By comparison, the base catalysed hydrolysis of the same series of methyl esters would involve the development of negative charge in the transition state relative to the ground state, hence the reaction would depend on both the steric and electronic effect of the substituent. Taft was also... 

Knochel s method provided the pentameric peptide 224. Hydrogenation followed by treatment of the resulting amino acid with EDC and HOBt afforded macrocycle 225. Hydrolysis of methyl ester 225, and imidazolone formation via the acid chloride, followed by Boc deprotection provided kapakahine F (219) in significant quantity. Final coupling of 219 with Boc-Phe-OH followed by Boc removal afforded kapakahine B (218) (Scheme 40). 

Table 16.5 Hydrolysis of methyl esters of a-amino acids attached to macronet isoporous polymer (CMDP, 5% - Support I) and styrene-0.8% DVB copolymer (Support II) [379]...

Taft Es Hydrolysis of methyl esters Steric size > I, more sensitive < 1, less sensitive... 

It has been shown that substituents and heterocyclic nitrogen are additive as regards their effects on the rates of alkaline hydrolysis of methyl esters of substituted pyridinecarboxylic acids (23). ... 

Pectinesterases (pectinmethylesterases or pectinpectyUiydro-lases) catalyse the hydrolysis of methyl esters to low esterified pectins, also known as pectic acids (Figure 4.20). The resulting acids react with the naturally present divalent ions, which may... 

Neighbouring group effect of thioacetal caused facile hydrolysis of methyl ester)... 

Geometrical isomeric mixtures of steroidal oxime esters have been evaluated for the enzymatic transformations. In this respect, the work by Adamczyk and co-workers [27] describes the use of lipase from CCL in the diastereoselective hydrolysis of 3-(0-carbox-ymethyl)oxime methyl esters, 17a-hydroxyprogesterone 122, progesterone 124, testosterone 126, and cortisol 128. CCL proved to be effective in carrying out hydrolysis of methyl esters of steroidal 3-carboxymethyl oximes in a mild manner affording the E and Z dia-stereoisomers 123/122, 125/124, 127/126, and 129/128 in different ratios. The enzyme exhibited a preference for the anti isomer (Table 11). The faster rate and greater selectivity observed for 128 is probably due to the cortisol derivative s better solubility in the reaction media. 

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