Amides carbodiimide hydrochloride

Molecules of interest that contain free amino groups can be coupled in aqueous solution to /S-poIy(L-malate) as amides using carbodiimides such as the water-soluble l-ethyl-3(3-dimethyIaminopropyl)carbodiimide hydrochloride (EDC) [2,12,20,21]. By this method, the molecules are attached randomly. A selective amide bond formation at the carboxylate terminus can be achieved... 

The reactions involved in an EDC-mediated conjugation are discussed in Chapter 3, Section 1.1 (Note EDC is l-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride MW 191.7 and is sometimes referred to as EDAC). The carbodiimide first reacts with available carboxylic groups on either the carrier or hapten to form a highly reactive o-acylisourea intermediate. The activated carboxylic group then can react with a primary amine to form an amide bond, with release of the EDC mediator as a soluble isourea derivative. The reaction is quite efficient with no more than 2 hours required for it to go to completion and form a conjugated immunogen. 

A mixture of 4 -[(methylsulfonyl)amino]-y-oxobenzenebutanoic acid and 1-hydroxybenzotriazole in dimethylformamide (DMF) under nitrogen, is treated with dibutylamine in DMF. The mixture is cooled in an ice bath and l-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC) added in portions over 5 min. The mixture is stirred in the cold 1 h and overnight at room temperature. The solvent is removed in vacuo (bath temperature 35°C). The residue is treated with ice and ethyl acetate and the organic layer washed sequentially with 0.5 N monopotassium sulfate, cold 4% NaHC03, cold water and finally brine. The organic solution is dried (Na2S04) and concentrated in vacuo. The N,N-dibutyl-y-oxo-4-[(methylsulfonyl)amino]benzenebutan-amide (crystallized from ethyl acetate-hexane) is obtained. 

Abbreviations used Dde, N-[l-(4,4-dimethyl-2,6-dioxocyclohexadiene)]-ethyl DIEA, diisopropylethylamine DMF, N,N-dimethylformamide EDC, l-Ethyl-3-(3 -dimethylaminopropyl)carbodiimide hydrochloride HOBt, 1-hydroxybenzotriazole NHS, N-hydroxysuccinimide NMP, l-methyl-2-pyrroIidinone PAL, Peptide Amide Linker [5-(4-(9-fluorenylmethyloxycarbonyl) aminomethyl-3,5-dimethoxyphenoxy) valeric acid] PyBOP, Benzotriazole-l-yl-oxy-trispyrrolidino-phosphonium hexafluorophosphate TFA, trifluoroacetic acid. 

Acylation of 5-substituted 6//-l,3,4-thiadiazines 172 with the carboxylic group of carboxysulfonamides was mediated by a mixture of A -ethyl-A -(3-dimethylamino propyl)carbodiimide hydrochloride, 1-hydroxybenzotriazole (HOBT), and 4-methylmorpholine in DMF at 5°C to yield l,3,4-thiadiazin-2-yl-2-[(phenylsulfonyl)amino]propan-amides 173 (Equation 22) <2001JME3231>. Analogous dihydroorotic acid derivatives 174 were also prepared. Such... 

Aiming at demonstrating the potentialities of the hexameric capsule as a substrate selective nanoreactor, Scarso and coworkers extended the concept to a stoichiometric reaction. In particular, the steric hindrance due to the confined space within the cavity of the capsule was exploited in the substrate selective amide synthesis mediated by the cationic condensing agent 1-ethyl-3-(-3-dimethylaminopropyl) carbodiimide hydrochloride [47]. Similarly to the encapsulation of other cationic species, the cationic condensing agent that in... 

Ferritin and bovine serum albumin (BSA) proteins can also chemically bond to nitrogen-doped MWNTs (CNx-MWNTs) through a two-step process of diimide-activated amidation. Firstly, carboxylated CNx-MWNTs were activated by N-ethyl-N -(3-dimethylaminopropyl)carbodiimide hydrochloride (EDAC), forming a stable active ester in the presence of N-hydroxysuccinimide (NHS). Secondly, the active ester was reacted with the amine groups on the proteins of ferritin or BSA, fornting an antide bond between the CNx-MWNTs and proteins. This two-step process avoids the intermolecular conjugation of proteins, and guarantees the uniform attachment of proteins on NTs (Scheme 12.3) [44]. 

Another potential problem with DCC is that at the completion of the reaction some DCU remains in solution with the product, necessitating additional purification. Water-soluble carbodiimide derivatives such as l-Cyclohexyl-3-(2-morpholinoethyl)carbodiimide Metho-p-toluenesulffonate and l-Ethyl-3-(3 -dimethylaminopropyl)carbodiimide Hydrochloride (EDCI) obviate this problem, as they are removed by a simple extraction. Many newer coupling agents have been developed for peptide synthesis and other acylation reactions. These include Benzotriazol-l-yloxytris(dimethylamino)phosphonium Hexafluorophosphate (BOP)," 0-Benzotriazol-l-yl-N,N,N, N -tetramethyluronium Hexafluorophosphate (HBTU)," Bis(2-oxo-3-oxazolidinyl)phosphinic Chloride (BOP-Cl), and (1 //-1,2,3-benzotriazol-1 -yloxy)tris(pyrTolidino)phosphonium hexafluorophosphate (PyBOP). In addition to linear and polymeric amides, lactams of various ring sizes have been synthesized using these methods (eq 1)."... 

Carbodiimides are, in general, useful compounds for effecting certain dehydrative condensations, e.g., in the formation of amides, esters, and anhydrides. These two crystalline water-soluble carbodiimides are especially useful in the synthesis of peptides and in the modification of proteins. The excess of reagent and the co-product (the corresponding urea) are easily separated from products with limited solubility in water. The hydrochloride is best employed in nonaqueous solvents (methylene chloride, acetonitrile, dimethylformamide). The methiodide is relatively stable in neutral aqueous systems, and thus is recommended for those media. 

Despite continnons progress in amide bond formation, the acylation of hydroxylamine nnder carbodiimide promotion is often contaminated by Af,0-diacylation even with sub-stoichiometric amounts of acids. Appendino and colleagues have developed a practical solution to the problem by combining the in situ activation of carboxylic acids 102 with the cyclic phosphonic anhydride PPAA (103), and the generation of hydroxylamine from its corresponding hydrochloride to form 104 (Scheme 54). 

Derivatives of carboxylic acids such as amides are relatively stable to hydrolysis and can exist in aqueous solutions, at least at pH 7. However, the important modification of this reaction, namely rapid one-step formation of amides in aqueous media at room temperature, has been proposed only in 2007. " Besides the selected amine, 2,2,2-trifluoroethylamine hydrochloride (TFEA), special catalyst should be used ethyl-[3-(dimethylamino)propyl]carbodiimide, C2H5-N=C=N-... 

P-Ser -] P-corticotropin-(l-13)-tridecapeptlde amide (l). The synthesis of I, shown in Fig. 1, was carried out by Dr. M. Brugger. It followed closely the one reported from our laboratory (I5) for the preparation of a-MSH. Use of the carbodiimide method to couple the protected 1-D-serine decapeptide 1-10 with the hydrochloride of the trlpeptide amide 11-15 (15) yielded the protected sequence 1-15 which was purified by column chromatography on silica gel. Removal of the protecting groups by treatment with trifluoro-acetic acid and subsequent ion exchange led to the acetate salt of the free peptide I in pure form. 

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