1-HYDROXYBENZOTRIAZOLE

PRODUCT IDENTIFICATION

H.S. CODE

TOXICITY

CLASSIFICATION

EXTRA NOTES

PHYSICAL AND CHEMICAL PROPERTIES

5 g/l at 30 C

AUTOIGNITION

NFPA RATINGS

Health hazard: 0, Fire: 0, Reactivity Hazard: 4

REFRACTIVE INDEX

Stable under ordinary conditions

EXTERNAL LINKS & GENERAL DESCRIPTION

Wikipedia Linking

Google Scholar Search

Drug Information Portal (U.S. National Library of Medicine) - HOBt

PubChem Compound Summary - HOBt

http://www.arkat-usa.org/
Coupling Additives: Ideally, peptide bond formation should be fast, quantitative and carried out under mild conditions without affecting adjacent stereogenic centers, without side reactions and with easily removable side products. Although much progress has been achieved, some problems still remain. A recent comprehensive review of all coupling reagents and their acronyms is available. While the cyclization of homo- or heterodetic peptides is not addressed directly in this report, it is an important application of coupling reagents. In such cases, it should be remembered that intramolecular cyclizations are best carried out in highly diluted media (10-3 to 10-4 M) and as a result the coupling reaction will be slow. Therefore, the activated intermediate should not undergo unimolecular or solvent-induced decomposition. The amino group is best protected as a carbamate and special conditions may be needed for sterically hindered and N-methylated amino acids. Tetramethyluronium derivatives have been reported to be used in end-capping the amino group involved in the macrocyclization. Additives are used in coupling reactions to inhibit side reactions and reduce racemization. The rate of racemization of an alpha-amino acid derivative depends on temperature, reaction conditions and its substituents. A considerable increase in ease of racemization is also due to the activating acyl substituent. An increase in acylating efficiency (measured by the rate constant) is achieved by thermodynamic activation of the acyl function and this activation increases the vulnerability to racemization. Epimerization occurs as an activated acyl derivative is formed or when it is reacted with the amino function.

Local:
Carbodiimides are a group of organic compounds which have the resonance formula  N=C=N. Carbodiimide is formed by dehydration of urea or from thiourea. Carbodiimides are readily reacts with various form of amines and hydroxyl functional groups. Carbodiimides are used as dehydration agents and as activating agent of carboxylic acids to form esters or amides. The disubstituted carboxyl activating agents are used for crosslinking proteins to nucleic acids and formation of immunoconjugates in peptide synthesis. N,N'-dicyclohexylcarbodiimide (DCC) is one of the most common peptide coupling agents. It is a low melting point waxy solid; insoluble in water but highly soluble in common organic solvents like acetonitrile dichloromethane, dimethylformamide, and tetrahydrofuran. DCC is a potent allergen. N,N'-diisopropylcarbodiimide (DIC) is an alternative to DCC, DIC is a liquid and is not an allergen. 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) is a water-soluble activating agent for amide bonding with primary amines. It also activates phosphate groups. Typically, it is utilized in the pH range 4.0-6.0 without buffers. In particular, amine and carboxylate buffers should be avoided. Carbodiimides are so active and cause racemization of the amino acid. Active esters are less reactive and less in danger of racemization. 1-Hydroxybenzotriazole (HOBt) and 1-hydroxy-7-aza-benzotriazole (HOAt) are substances that react with the O-acylurea to form active esters. HOAt is a condensation additive in peptide synthesis. It efficiently speeds up coupling process, reduces the loss of chiral integrity, and provides a visual indication (yellow to colorless) of the reaction course. Other active esters exit as non-nucleophilic anionic salts of uronium or phosphonium such as O-(Benzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate(HBTU), O-(7-Azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate (HATU), (Benzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate (PyBOP).

APPEARANCE

PURITY (HPLC)

98.0% min

WATER

6.0 - 12.0% max

157 C min

APPEARANCE

PURITY (HPLC)

98.0% min

WATER

1.0% max

157 C min

Hazard OVERVIEW

Flammable solid

GHS

PICTOGRAMS

HAZARD STATEMENTS

H228  Causes serious eye irritation

PRECAUTIONARY STATEMENTS

P210 Keep away from heat/sparks/open flames/hot surfaces. - No smoking.

F Highly Flammable

RISK PHRASES

5  Heating may cause an explosion
11  Highly Flammable

SAFETY PHRASES

15 Keep away from heat
16  Keep away from sources of ignition - No smoking
35  This material and its container must be disposed of in a safe way