Esters carbodiimide hydrochloride

Scheme 9. N-Ras peptide synthesis employing choline esters as C-terminal protecting group. EDC 1-ethyl-3 (dimethylamino)propyl-carbodiimide hydrochloride, HOBt 1-hydroxybenzo-tri azole...

Pyrazolooxazepine 153 was synthesized starting from the condensation of hydrazinol 151 with enaminoketone 150. When the isolated ester intermediate 152 (R = OMe) was saponified, ester hydrolysis afforded acid 152 (R = H), which cyclized on subsequent treatment with l-ethyl-3-[3-(dimethylamino)propyl] carbodiimide hydrochloride (EDC) and 1-hydroxybenzotriazole (HOBt) to form oxazepine 153 (Scheme 22) <2003TL5867>. 

DEHYDRATION Boron trioxide. p-CMoro-phenyl chlorothionoformate. Dicyclohexyl-carbodiimide. Diethyl(2-chloro-l,l,2-tri-fluoroethyOaminc. Phosphoryl chloride N -Dimethylformamide. Polyphosphate ester. Pyridine hydrochloride. 

Figure 2 Reaction scheme for the coupling of desaminotyrosine and tyrosine alkyl esters to obtain a diphenolic monomer which carries an alkyl ester pendent chain (Y). Four specific monomers having an ethyl, butyl, hex)4 and octyl ester pendent chain were investigated in detail. EDC = ethyl-3-(3 -dimethylamino)propyl carbodiimide hydrochloride salt (Hooper, 1995).

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]. 

PGIP, purified fi om P.vulgaris hypocotyls [11], was immobilized to the sensor ch via amine coupling. A continuous flow of HBS buffer (5 pl/min) was mantained over the sensor surface. The carboxylated dextran matrix of the sensor surface was first activated by a 6-min injection of a mixture of N-hydroxy-succinimide and N-ethyl-N - (3-diethylaminopropyl) carbodiimide, followed by a 7-min injection of PGIP (lOng/pl in 10 mM acetate, pH 5.0). Hie immobilization procedure was con leted by a 7-min injection of 1 M ethanolamine hydrochloride to block the remaining ester groups. 

The carbodiimide of choice used to couple cystamine to carboxylate- or phosphate-containing molecules is most often the water-soluble carbodiimide, EDC hydrochloride Chapter 3, Section 1.1). This reagent rapidly reacts with carboxylates or phosphates to form an active ester intermediate, which is highly reactive toward primary amines. The reaction is efficient from pH 4.7 to 7.5, and a variety of buffers may be used, providing they don t contain competing groups. 

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. 

CARBAMIC acid, krt-BUTYL ESTER, 48, 32 Carbazole, 2-nitro-, 46, 85 Carbazoles, from o-azidobiphenyls,46,SS from o-nitrobiphenyls and triethyl phosphite, 48, 115 2-Carbethoxycyclodecanone, 47, 22 2-Carbethoxycyclododecanone, 47, 22 2-Carbethoxycyclohexanone, 45, 82 2-Carbethoxycyclononanone, 47, 22 2-Carbethoxycyclooctanone, 47, 20 t-Carbinamines, see /-Alkylamines Carbodiimide, [3-(dimethylamino)-propyl]ethyl-, hydrochloride, 48, 83... 

Carbodiimides are known to react with primary amines to form guanidines.f In the case of amino acid esters, a subsequent elimination of alcohol is possible with formation of an imino-hydantoin species (Scheme 8). However, these reactions usually require higher temperatures or the occurrence of acid catalysis and therefore can be neglected when unprotonated amino acid derivatives are acylated using carbodiimides. On the other hand, this side reaction becomes more important when protonated amino acids (i.e., amino acid ester hydrochlorides) are coupledf and these byproducts may occur. 

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