TentaGel supported active esters analogous to those prepared from solution-phase 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. (C) 2002 Elsevier Science Ltd. All rights reserved.