N-hydroxysuccinimide: Difference between revisions
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'''N-hydroxysuccinimide''' (NHS) is chemical used to form semi-stable, but reactive, [[ester]]s from [[carboxylic acid]]s. Such NHS esters can be stored for a relatively long time if kept cold and dry. NHS is typically used in conjunction with a dehydrating reactent, often a [[carbodiimide]] such as [[EDAC]], [[DCC]] or [[DIC]]. A very similar compound, sulfo-NHS, which contains an SO<sub>3</sub><sup>-</sup> group on one of the two aliphatic carbons, is often used instead. | '''N-hydroxysuccinimide''' (NHS) is chemical used to form semi-stable, but reactive, [[ester]]s from [[carboxylic acid]]s. Such NHS esters can be stored for a relatively long time if kept cold and dry. NHS is typically used in conjunction with a dehydrating reactent, often a [[carbodiimide]] such as [[EDAC]], [[DCC]] or [[DIC]]. A very similar compound, sulfo-NHS, which contains an SO<sub>3</sub><sup>-</sup> group on one of the two aliphatic carbons, is often used instead. | ||
== Carboxylate Activation with Carbodiimide and NHS == | |||
{{Image|Carbodiimide coupling via NHS ester.png|left|350px|'''Scheme 1''':Coupling of a carboxylic acid and a primary amine via O-acylisourea ester and NHS ester intermediates.}} | |||
As depicted in '''Scheme 1''', the carbodiimide-mediated coupling of a carboxylic acid ('''1''') with a primary amine first progresses through an unstable intermediate, an O-acylisourea ester ('''3''') compound formed by the reaction of the carbodiimide ('''2''') with the carboxylic acid ('''1'''). Because this intermediate is unstable, it is often the case that either NHS ([[N-hydroxysuccinimide]]) '''4''' or sulfo-NHS is added to the carboxylic acid together with the carbodiimide, in order to form an NHS-ester ('''5'''), which is a much more stable compound that remains reactive with amines. Upon the final addition of an amine ('''6'''), the final desired coupling product, an amide ('''7'''), is formed by displacement of the NHS. | |||
Revision as of 08:27, 7 October 2009
N-hydroxysuccinimide (NHS) is chemical used to form semi-stable, but reactive, esters from carboxylic acids. Such NHS esters can be stored for a relatively long time if kept cold and dry. NHS is typically used in conjunction with a dehydrating reactent, often a carbodiimide such as EDAC, DCC or DIC. A very similar compound, sulfo-NHS, which contains an SO3- group on one of the two aliphatic carbons, is often used instead.
Carboxylate Activation with Carbodiimide and NHS
As depicted in Scheme 1, the carbodiimide-mediated coupling of a carboxylic acid (1) with a primary amine first progresses through an unstable intermediate, an O-acylisourea ester (3) compound formed by the reaction of the carbodiimide (2) with the carboxylic acid (1). Because this intermediate is unstable, it is often the case that either NHS (N-hydroxysuccinimide) 4 or sulfo-NHS is added to the carboxylic acid together with the carbodiimide, in order to form an NHS-ester (5), which is a much more stable compound that remains reactive with amines. Upon the final addition of an amine (6), the final desired coupling product, an amide (7), is formed by displacement of the NHS.