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Alkaline hydrolysis of esters is also known as saponification. A base such as sodium hydroxide is required in stochiometric amounts. Unlike acid-catalyzed ester hydrolysis, it is not an equilibrium reaction and proceeds to completion. Hydroxide ion attacks the carbonyl carbon to give a tetrahedral intermediate, which then expels an alkoxide ion.
Reaction of the product with hydrogen chloride then cleaves the tert-butyl group to give the half acid (3). [19] Coupling of that acid to the secondary amine on tetrahydroisoquinoline (4) gives the corresponding amine. The tert-butyl ester in this product is again cleaved with hydrogen chloride to afford moexipril (5).
In pharmacology, the term mechanism of action (MOA) refers to the specific biochemical interaction through which a drug substance produces its pharmacological effect. [2] A mechanism of action usually includes mention of the specific molecular targets to which the drug binds, such as an enzyme or receptor . [ 3 ]
Reaction between acetic acid and salicylic acid can also form aspirin but this esterification reaction is reversible and the presence of water can lead to hydrolysis of the aspirin. So, an anhydrous reagent is preferred. [27] Reaction mechanism Acetylation of salicylic acid, mechanism
The hydrolysis reaction of the carboxyl ester leads to the formation of an acyl-enzyme and free choline. Then, the acyl-enzyme undergoes nucleophilic attack by a water molecule, assisted by the histidine 440 group, liberating acetic acid and regenerating the free enzyme. [18] [19]
Pig liver esterase (PLE) is a widely used enzyme for asymmetric ester hydrolysis. Although it was originally used for the desymmetrizing hydrolysis of glutarate esters, [3] PLE also hydrolyzes malonates, cyclic diesters, monoesters, and other substrates. Active site models have been advanced to explain the selectivity of PLE. [4]
Ortho esters are readily hydrolyzed in mild aqueous acid to form esters: . RC(OR ′) 3 + H 2 O → RCO 2 R ′ + 2 R ′ OH. For example, trimethyl orthoformate CH(OCH 3) 3 may be hydrolyzed (under acidic conditions) to methyl formate and methanol; [5] and may be further hydrolyzed (under alkaline conditions) to salts of formic acid and methanol.
The enzyme carboxylesterase (or carboxylic-ester hydrolase, EC 3.1.1.1; systematic name carboxylic-ester hydrolase) catalyzes reactions of the following form: [1] a carboxylic ester + H 2 O ⇌ {\displaystyle \rightleftharpoons } an alcohol + a carboxylate