Hydroxybenzo-triazoles

Starting with the tetraethyl ester of DOTA the potassium salt of the triester 31 has been obtained by a partial saponification. To the solution of this compound in anhydrous tetrahydrofuran dicyclohexylcarbodiimide and 1-hydroxybenzo-triazole has been added followed by tris(2-aminoethyl)amine. Subsequent hydrolysis of the ester groups yielded the nonaacid 32. 

FIGURE 7.14 Acylation of N-nucleophiles using polymer supported 1-hydroxybenzo-triazole derivative. 

Koenig W, Geiger R, New methods for the synthesis of peptides Activation of the carboxyl group with dicyclohexylcarbodiimide by using 1 -hydroxybenzo-triazoles as additives, Chem. Ber., 103 788-798, 1970. 

In another vessel, a mixture consisting of A-f-butoxycarbonylalanine (6.5 mmol), l-(3-dimethyl-aminopropyl)-3-ethylcarbodiimide (6.5mmol), and 1-hydroxybenzo-triazole (6.5 mmol) dissolved in 10 ml DMF was stirred 1 hour and then concentrated. This residue was then added to the first vessel and stirred 3 days. The reaction was quenched with aqueous KHS04, then diluted with EtOAc, washed with water, aqueous NaHC03, and brine, and dried over Na2S04. The mixture was concentrated, triturated with diethyl ether to remove residual DMF, and the product isolated as a white solid in 73% yield. 

Aminocarboxylic ester, 9-cascade aminomethane [3] (2-aza-oxopentylidyne) t-butyl propionate (4.58 g), 4-benzyloxybutyric acid (0.61 g), dicyclohexylcarbodiimide (0.66 g) and 1-hydroxybenzo-triazole (0.43 g) were dissolved in 50 ml DMF and stood 24 hours at ambient temperature. The solvent was removed in vacuo, the residue taken up in EtOAc, washed with 10% cold HCl, water, 10% NaHC03, and concentrated brine. Thereafter the material was dried, purified by chromatography on silica using hexane/EtOAc, 1 1, and the product isolated in 60% yield. 

Protection of carboxylic acids. The 2-(2-pyridyl)ethyl group is useful for protection of amino acids. The esters are obtained by reaction with 1 and DCC/1-hydroxybenzo-triazole. The group provides higher solubility in protic solvents, and is stable to both acids and bases. It is removed by treatment with methyl iodide and a weak base. 

The salt is prepared by reaction of hydroxybenzo-triazole with tetramethyluronium chloride hexafluorophosphate. 

W-(3-dimethylaminopropyl)-W -ethylcarbodiimide (EDCI) and 1-hydroxybenzo-triazole (HOBt) in CH2CI2 (63) [48], Ester derivatives were also prepared from 2-epi-Sl by alkylating with appropriate acid chloride or anhydrides and Et3N in CH2C12 [34], In addition, 57 was treated with a mixture of formic acid and acetic anhydride (Ac20) to yield the C-2 formate (64) [49]. 

PEPTIDE SYNTHESIS r-Amyl chloro-formate. f-Butyl azidoformate. Diethyl methyleneraalonate. N-Ethoxycarbonyl-2-ethoxy-l,3-dihydroquinoline. Hexamethylphosphoric triamide. 1-Hydroxybenzo triazole. Triphenylphosphine—2,2 -Dipyridyl disulfide. Triphenyl phosphite. 

Obviously, the incorporation of an electron-withdrawing substituent in the polymer-supported benzotriazole ring should enhance its reactivity. Thus, the sulfonamide-substituted HOBt resin 34 (Section 7.3) has been obtained by reaction of aminomethylated divinylbenzene cross-linked polystyrene with the sulfonyl chloride 116 to give supported sulfonamide 117, followed by typical hydroxybenzo-triazole formation (Scheme 7.37) [128]. The effect induced by the sulfonamide group was determined by measuring the acidity of non-polymeric analogues, showing a pKa of 3.59 for the sulfonamide-substituted HOBt, and a pKa of 4.64... 

The sulfonate (1) is prepared by the reaction of 6-chloro-N-hydroxybenzo-triazole with p-chlorobenzenesulfonyl chloride under Schotten-Baumann conditions. ... 

UV absorbers transform high-energy UV radiation into comparatively harmless heat. Examples of UV absorbers include hydroxybenzophenones, hydroxybenzo-triazoles, and cinnamic acid ester. 

Polystyrene Olive oil and aqueous extraction liquids, sunflower oil, linseed oil Santonox R antioxidant and hydroxybenzo-triazoles Spectrophotometric and polarographic techniques [151- 153]... 

Previously, we clarified the complexation of chitosan with hydroxybenzo triazole, resulting in a water soluble system of chitosan (27-25). The system is attractive since it provides the reaction, and especially the conjugation, in aqueous media. Based on this approach, the present work, thus, (i) demonstrates a simple but effective crosslink reaction by using poly(ethylene glycol) as the crosslinker to obtain a superabsorbent gel in aqueous, and (ii) proposes... 

In the dicyclohexylcarbodi-imide method of peptide-bond formation, the problems of racemization and rearrangement to A-acylureas can be avoided by interception of the intermediate activated ester with 1-hydroxybenzo-triazole. The ester so produced functions efficiently in amide-bond formation similar beneficial properties have already been noted with iV-hydroxy-succinimide. 

PMB = pentamethylbenzyl. First step N,N -dicydohexylcarbodiimide/4-dimethyl-aminopyridine (DCC/DMAP). Second step HBr/Acetic acid. Third step Triethylamine, N,N -dicyclohexylcarbodiimide/ 1-hydroxybenzo-triazole (DCC/HOBt). 

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