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N-Hydroxysuccinimide (NHS) is an organic compound with the formula (CH 2 CO) 2 NOH. It is a white solid that is used as a reagent for preparing active esters in peptide synthesis. It can be synthesized by heating succinic anhydride with hydroxylamine or hydroxylamine hydrochloride. [2]
Active esters are mainly used as acylating agents. They undergo the same reactions as their unactivated analogues but do so more rapidly. They are prone to hydrolysis, for example. Of great interest is the enhanced reactivity of active esters toward amines to give amides. [1] [2]
An example of an ester formation is the substitution reaction between a carboxylic acid (R−C(=O)−OH) and an alcohol (R'OH), forming an ester (R−C(=O)−O−R'), where R and R′ are organyl groups, or H in the case of esters of formic acid.
The ester linkage is formed between the N-hydroxyphthalimide and a carboxylic acid by elimination of water, the coupling achieved with N,N′-dicyclohexylcarbodiimide (DCC). For peptide synthesis, the N-terminus of the growing peptide is protected with tert-butyloxycarbonyl while its C-terminus (Z–NH–CH(R)–COOH) is coupled to N ...
The Reformatsky reaction (sometimes transliterated as Reformatskii reaction) is an organic reaction which condenses aldehydes or ketones with α-halo esters using metallic zinc to form β-hydroxy-esters: [1] [2] The Reformatsky reaction. The organozinc reagent, also called a 'Reformatsky enolate', is prepared by treating an alpha-halo ester ...
An example is the reaction of benzophenone with diethyl succinate: [3] A reaction mechanism that explains the formation of both an ester group and a carboxylic acid group is centered on a lactone intermediate ( 5 ):
Krapcho decarboxylation is a chemical reaction used to manipulate certain organic esters. [1] This reaction applies to esters with a beta electron-withdrawing group (EWG).. The reaction proceeds by nucleophilic dealkylation of the ester by the halide followed by decarboxylation, followed by hydrolysis of the resulting stabilized carbanion.
Aside from the acid chloride substrate, three reagents are required: diazomethane, water, and a metal catalyst. Each has been well investigated. The diazomethane is required in excess so as to react with the HCl formed previously. [2] Not taking diazomethane in excess results in HCl reacting with the diazoketone to form chloromethyl ketone and ...