The 5,6- and 4,5-benzo derivatives of 1-hydroxy-7-azabenzotriazole.
[structure: see text]. Syntheses of the two benzo derivatives of HOAt are described. Conversion of the two isomers to the corresponding onium-style coupling reagents gave in one case a guandinium species 14 and in the other, presumably as a result of steric factors, a uronium species 15. The two systems are compared as to their effectiveness in peptide coupling processes.