EDCI 1 -Ethyl-3- carbodiimide

Eledroosmotic flow (EOF) conditions were applied and yielded only 10% conversion with constant reactant movement [9]. The use of stopped-flow techniques, which periodically push and mix the flow, led to a 50% increase in yield. A change in the coupling agent from l-(3-dimethylaminopropyl)-3-ethyl-carbodiimide hydrochloride (EDCI) to dicyclohexylcarbodiimide (DCC) for reasons of limited solubility resulted in a 93% yield of the dipeptide. Batch P-dipeptide synthesis using EDCI gave a yield of 50% [6]. 

Boc-D-alanine and (S)-a-methylbenzylamine react to give the corresponding dipep tide via an EDCI [3-ethyl-l-(3-dimethylaminopropyl)-carbodiimid] coupling [86], control experiment, Boc-t-alanine and (S)-a-methylbenzylamine also reacted. 

Well established carbodiimide-based methods for esterifying carboxylic acids can be used to prepare te/7-butyl esters. In the example shown in Scheme 638, dicydohexylcarbodiimide (DCC) served as the dehydrating agent,94 but 1-ethyl-3-[3-dimethylamino)propyl]carbodiimide (EDCI) works equally well and the by-product urea is water soluble in the latter case 95... 

EDCI N-ethyl-lV -(3-dimethylaminopropyl)carbodiimide HOBt 1-hydroxy-l//-benzotriazole LDA lithium diisopropylamide... 

Polystyrene-supported tethered l-ethyl-3-(3-dimethylamino-propyl)carbodiimide hydrochloride (PS-EDC or PS-EDCI, 11) is also a commercially available, frequently used resin-supported carbodiimide [25], which is highly effective in the coupling of carboxylic acids and amines, in the absence of any additive the use of chloroform as solvent is essential. 

Miller, M.M. and Boger, D.S. (2005) Polystyrene-1-ethyl-3-(3 -dimethylaminopropanej-carbodiimide Hydrochloride (PS-EDCI), in Handbook of Reagents for Organic Synthesis, Reagents for Glycoside, Nucleotide and Peptide Synthesis (ed. D. Crich), John Wiley Sons Ltd, Chichester, pp. 529-33. 

Key i) EDCI, CeFsOH, rt EDCI = l-ethyl-3-(3-dimethylaminopropyl)carbodiimide. 

Derivatization of acids with 2-nitrophenylhydrazine has been described in a number of publications [111-115]. N,N -Dicyclohexylcarbodiimide (DCCI) [111] or 1-ethyl-3-(dimethylaminopropyl)carbodiimide (EDCi) (114,115) was used for the activation of the carboxylic acid function. Normally the derivatives were detected at 550 nm. Miwa and Yamamoto [115] applied this method to the determination of urinary dicarboxylic acids, which reacted with 2-nitrophenylhydrazine to form monohydrazides. The adds were extracted from acidified urine with ethyl acetate and dried. After derivatization, the monohydrazides of the dicarboxylic acids were first separated from the hydrazides of monocarboxylic acids and other interfering substances by a two-step extraction. The recoveries varied from 27.6-103.1%, depending on the polarity and the water solubility of the acids. The separation of monohydrazides of 11 straight- and branched-chain dicarboxylic acids was performed on an ODS column at 40 °C by isocratic elution with acetonitrile-phosphate buffer containing counter-ions such as tetramethylammonium as mobile phase. Detection was at 400 nm. 

Figure 5 The palindromic hexadeoxynucleotide 3 is capable of templating its own formation from a nucleophilic trideoxynucleotide 1 and an electrophilic trideoxynucleotide 2. EDCI = l-ethyl-3-(3 -dimethylaminopropyl)carbodiimide.

The MAf -dicyclohexylurea that is produced in peptide couplings with DCCI is soluble in the same solvents as the product, making it more difficult to separate the by-products during purification. An alternative carbodiimide used in peptide synthesis is l-ethyl-3-(3-dimethylaminopropyl) carbodiimide, known as EDCI. Both EDCl and the urea that is produced from it are water-soluble and can be more easily separated from the peptide product. EDCI can also be used in organic solvents. 

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