Preparation of active esters on solid support for aqueous-phase peptide couplings

TentaGel supported active esters analogous to those prepared from solution-phase reagents such as 1-hydroxybenzotriazole, N-hydroxysuccinimide, and pentafluorophenol were prepared and examined for their ability to effect aqueous-phase peptide couplings. HOBt esters showed high hydrolysis rates, relative to peptide coupling, while active esters derived from 4-hydroxy-2,3,5,6-tetrafluorobenzoic acid produced mainly dipeptide coupling products when treated with amino acids in water.