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HBTU (2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexauorophosphate), a coupling reagent commonly used in solid phase peptide synthesis. After being introduced in 1978, this agent shows popularity in chemistry and industry use due to its mild activating properties. Moreover, it also shows resistance against racemization. Low tendency for racemization is a key requirement for peptide synthesis. Especially for solid phase peptide synthesis, quantitative yields with short reaction times are crucial in order to make the synthesis of large peptides feasible. [1]

In vitro: Peptide synthesis relied mostly on efficient and safe coupling reagents. HBTU was proved to transform carboxylic acids into azides efficiently and practically. The process might be applied to a wide range of carboxylic acids including N-protected amino acids. In addition, HBTU was of great value in one-pot synthesis of dipeptidyl urea esters, ureas, and carbamates from acids. The advantages of HBTU included the following points: 1) Non-explosive and therefore more suitable for solution/solid phase peptide synthesis. 2) High solubility and stability in classical solvents. 3) Feasible for colorimetric reaction monitoring. [2]

In vivo: So far, no in vivo data has been reported.

Clinical trial: So far, no clinical trial has been conducted.

References:
[1]Adam S.  HBTU: a mild activating ageiw of muramic acid. Bioorg Med Chem Lett. 1992 Mar; 2(6): 571-4.
[2]Knorr R, Trzeciak A, Bannwarth W and Gillessen D.  New coupling reagents in peptide chemistry. Tetrahedron Lett. 1989; 30(15): 1927-30.