Efficient stereoselective hydrolysis of enantiomeric amino acid esters by bilayer vesicular systems which include di- or tri-peptide histidine catalysts

Abstract

When the stereoselective hydrolysis of enantiomeric amino acid esters, Me[CH₂]_nCONH[graphic omitted]H(R)CO₂C₆H₄NO₂-p[R = PhCH₂(6a), Me₂CHCH₂(6b), or Me (6c); n= 0–12], by the bilayer vesicular systems of histidine catalysts (L-histidine or di- or tri-peptide L-histidine derivatives) and a double-chain surfactant, (Me[CH₂]₁₁)₂NMe₂Br (5), was carried out at 4–25 °C in Tris buffer (pH 7.68) in 3%(v/v) MeCN–H₂O, the efficient stereoselective reaction was realized with dipeptide histidine catalysts such as Z-L-Phe-L-His (2a) and Z-L-Leu-L-His (2c) and the surfactant (5) through the two stereoselective processes (viz., binding and hydrolysis of the L-substrate by the catalytic vesicular system). In the hydrolysis of the substrates (6a; n= 8) possessing an appropriately long N-acyl chain and a hydrophobic substituent R (R = PhCH₂) by the gel-phase vesicular catalyst composed of (2c) and (5) at 4 °C, the stereoselection of the enantiomeric substrate was considerably enhanced by the close proximity of the catalyst and the substrate, giving an enantiomer rate ratio (L/D) of 148.2. The mode of interaction between the catalyst and the substrate is discussed in relation to the preferential attack of the histidine catalyst on the L-substrate in the vesicle–substrate complex.