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. 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 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 molecules and to improve the efficiency of peptide synthesis.

Use in peptide synthesis

Automated peptide synthesis 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, 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 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