Replacing carboxylate group with

Another reaction that is occasionally used for conversion of carboxylic acids to the corresponding amine with loss of carbon dioxide is the hypobromite oxidation of amides. The iV-bromoamide is presumably an intermediate. This reaction is known as the Hofmann rearrangement. The migration is believed to be concerted, with elimination of bromide ion. It can be used to replace carboxyl groups with... 

Amidation refers to the replacement of a protein s C-terminal carboxyl group with an amide group (COOH — CONH2). This PTM is usually characteristic of peptides (very short chains of amino acids), as opposed to the longer polypeptides, but one therapeutic polypeptide (salmon calcitonin, Chapter 11) is amidated, and amidation is required for full functional activity. Overall, the function(s) of amidation is not well understood, although in some cases at least it appears to contribute to peptide/polypeptide stability and/or activity. 

FI GURE 4.3 Structures of allocholic acid (petromyzonol sulfate is identical apart from replacement of the carboxyl group with sulfate), taurine-conjugated bile acid, and geosmin. 

Heterocyclic sulfonamide 36 is thermally decarboxylated in low to modest yields to give 44 (Equation 9). Inclusion of other electrophiles in the solution also allowed the replacement of the carboxylate group with Br, NO2, and COCl as well as H <2005HCA1208>. 

Replace the carboxyl group with a hydrogen and you have the structure of cadaverine. Interestingly, the voodoo lily transforms its lysine into cadaverine in order to attract pollinators, usually those that normally dine on the carcasses of dead animals. 

Formal replacement of the hydroxyl moiety of the carboxyl group with a halogen (X), an acyloxy group (R-CO-O—), an alkoxy group (RO—), or an amino group (NH2) leads to ... 

We therefore altered Asp76 of aspergillopepsin I to Asn in order to replace the carboxyl group with an uncharged side chain very similar in size to that of Asp, and to Glu so that the... 

The incoming monomer unit would then be forced, either because of steric interactions, or by the interaction of its carboxyl group with lithium at the chain-end, to add in a specific manner to re-form the same loose ring structure present initially. One variant of this mechanism [192] involves a covalently bonded six membered ring formed by enolization of the active chain end followed by alkoxide ion attack on the penultimate carboxyl group. In polar solvents, or in the presence of moderate amounts of them, competition for solvation of the counter-ion would be produced and the intramolecular solvation producing the stereospecificity would be reduced in effectiveness as the ether concentration is increased. Replacing the lithium counter-ion with sodium or other alkali metal would be... 

Electrolysis of a-sulfenyl carboxylic acids in protic solvents gives ketones, presumably via replacement of the carboxyl group with alkoxyl or acetoxyl groups and a subsequent two-electron oxidation of the sulfenyl moiety [Eq. (32)]. (This discussion is postponed to Sec. IV.D.)... 

This explanation is supported by the inhibitory activities of the series of adamantanes shown in Figure 4. The simplest compound, adamantane-l-carboxylic acid, is a potent inhibitor, but introduction of a second carboxyl group results in substantially weaker inhibition. Activity is partially restored by the replacement of either or both carboxyl groups with acetic acid functions, in which the additional methylene groups may serve to reduce repulsive interactions. The inhibitory activity of these analogues thus emphasizes the importance of correct substituent orientation in the design of transition state analogues. 

Carboxylic acids are one of the most fundamental and important groups of compounds in organic chemistry. Chalcogenocarboxylic acidsy RCEE H (E, E =0, S, Se, Te), are derived from carboxylic acids by replacing one or both oxygen atoms of the carboxyl group with S, Se or Te. 

Breaking cystine residue disulfide cross-links [13], or breaking peptide bonds in the protein main-chains, increases the equilibrium water content of wool at RHs above 80%. Acetylation of amino and hydroxyl groups, or esterification of carboxylic add groups in amino add side-chains, decreases the EWC of wool at low RHs because each treatment replaces hydrophilic groups with less hydrophilic groups. 

This technique based on the derivatization of the samples by phosphytUation allows both quantitative and qualitative characterization of all the labile OH groups, namely, the aliphatic OH, different phenohc OH, and carboxylic OH. This method is based on the replacement of the acidic hydrogens of the hydroxyl and carboxyl groups with the phosphorus reagent 2-chloro-4,4,5,5-tetramethyphospholane and the use of P-NMR spectroscopy to identify the phosphitylated compounds [142, 144,145]. 

By replacing the carboxyl group with a tetrazole system, the bio-availability is substantially increased while maintaining a similar acidity ... 

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