Stereoselective micellar catalysis. Part 4. Catalytic hydrolyses of enantiomeric esters by dipeptide derivatives containing a histidyl residue

Abstract

The rate constants for hydrolyses of the enantiomers of various amino acid p-nitrophenyl esters catalysed by optically active dipeptide catalysts containing a histidyl residue have been determined at pH 7.30, 0.02M-phosphate buffer, and 25°C in the presence of cetyltrimethylammonium bromide micelles. The dipeptide catalysts demonstrate greater stereoselectivity than simple optically active catalysts. The structural effects of catalysts and substrates are examined by investigation of the rate constants and stereoselectivities. The role of their hydrophobicity and their stereoselective reaction mechanism are discussed.