Hydroxybenzotriazole (abbreviated HOBt) is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...

that is a derivative of

benzotriazole Benzotriazole (BTA) is a heterocyclic compound with the chemical formula C6H5N3. Its five-membered ring contains three consecutive nitrogen atoms. This bicyclic compound may be viewed as fused rings of the aromatic compounds benzene and triazole. ...

. It is a white crystalline powder, which as a commercial product contains some water (~11.7% wt as the HOBt monohydrate crystal). Anhydrous HOBt is explosive. It is mainly used to suppress the

racemization In chemistry, racemization is a conversion, by heat or by chemical reaction, of an optically active compound into a racemic (optically inactive) form. This creates a 1:1 molar ratio of enantiomers and is referred too as a racemic mixture (i.e. con ...

of single-

enantiomer In chemistry, an enantiomer ( /ɪˈnænti.əmər, ɛ-, -oʊ-/ ''ih-NAN-tee-ə-mər''; from Ancient Greek ἐνάντιος ''(enántios)'' 'opposite', and μέρος ''(méros)'' 'part') – also called optical isomer, antipode, or optical ant ...

chiral Chirality is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is distinguishable from ...

molecules and to improve the efficiency of

peptide synthesis In organic chemistry, peptide synthesis is the production of peptides, compounds where multiple amino acids are linked via amide bonds, also known as peptide bonds. Peptides are chemically synthesized by the condensation reaction of the carboxyl ...

Use in peptide synthesis

Automated

involves the condensation of the amino group of protected

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

s with the activated ester. HOBt is used to produce such

activated ester In organic chemistry, an active ester is an ester functional group that is highly susceptible toward nucleophilic attack. Activation can be imparted by modifications of the acyl or the alkoxy components of a normal ester, say ethyl acetate. Typical ...

s. These esters are insoluble (like the N-hydroxysuccinimide esters) and react with amines at ambient temperature to give amides. HOBt is also used for the synthesis of amides from

carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxylic ...

s aside from amino acids. These substrates may not be convertible to the

acyl chloride In organic chemistry, an acyl chloride (or acid chloride) is an organic compound with the functional group . Their formula is usually written , where R is a side chain. They are reactive derivatives of carboxylic acids (). A specific example o ...

s. For instance amide derivatives of ionophoric

antibiotics An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention o ...

have been prepared in this way.{{cite journal, last=Łowicki, first=Daniel, author2=A. Huczyński , author3=M. Ratajczak-Sitarz , author4=A. Katrusiak , author5=J. Stefańska , author6=B. Brzezinski , author7=F. Bartl , title=Structural and antimicrobial studies of a new N-phenylamide of monensin A complex with sodium chloride, journal=

Journal of Molecular Structure Journal of Molecular Structure is a scientific journal published by Elsevier ScienceDirect since 1968. Its articles discuss molecular structure in chemistry. After the 2022 Russian invasion of Ukraine it said that it would no longer consider ma ...

, year=2009, volume=923, issue=1–3, pages=53–59, doi=10.1016/j.molstruc.2009.01.056, bibcode=2009JMoSt.923...53L

Safety

Due to reclassification as UN0508, a class 1.3C explosive, hydroxybenzotriazole and its monohydrate crystal are no longer allowed to be transported by sea or air as per 49CFR (

USDOT The United States Department of Transportation (USDOT or DOT) is one of the executive departments of the U.S. federal government. It is headed by the secretary of transportation, who reports directly to the President of the United States and ...

hazardous materials Dangerous goods, abbreviated DG, are substances that when transported are a risk to health, safety, property or the environment. Certain dangerous goods that pose risks even when not being transported are known as hazardous materials ( syllabi ...

regulations). However,

UNECE The United Nations Economic Commission for Europe (ECE or UNECE) is one of the five regional commissions under the jurisdiction of the United Nations Economic and Social Council. It was established in order to promote economic cooperation and i ...

draft proposal ECE/TRANS/WP.15/AC.1/HAR/2009/1 has been circulated to UN delegates and, if implemented, would amend current regulations thus allowing for the monohydrate crystal to be shipped under the less-stringent code of UN3474 as a class 4.1 desensitized explosive.

References

Peptide coupling reagents Benzotriazoles Biochemistry Reagents for biochemistry Biochemistry methods Hydroxylamines