STERIC CONTROL FOR THE HYDROLYSIS OF ENANTIOMERIC AND DIASTEREOMERIC ESTERS - A NEW DEVELOPMENT OF SUPRAMOLECULAR ASSEMBLIES

The remarkably high enantioselectivity (k(a,obsd)(L)/k(a,obsd)(D)=1000 ) was attained for the hydrolysis of amino acid eaters (N-dodecanoyl-D (L)-phenylalanine p-nitrophenyl eater : C-12-D(L)-Phe-PNP) catalyzed b y the active tripeptide loxycarbonyl)-L-phenylalanyl-L-histidyl-L-leuc ine; Z-Phe-His-Leu) in the coaggregate systems composed of 41 mol% hex adecyltrimethylammonium bromide (CTAB) and 59 mol% ditetradecyldimethy lammonium bromide (2C(14)Br) at the specific ionic strength (mu=0.02). With respect to the temperature dependence of hydrolysis in the coagg regate systems composed of native lipid (L-alpha-dipalmitoylphosphatid ylcholine; DPPC) and nonionic surfactant (alpha-[4-(I,1,3,3-tetramethy lbutyl) phenyl]-omega-hydroxydecakis(oxyethylene);Triton X-100), the e nantioselectivity was maximized at the phase transition temperature (T -e) and the hydrophobic microenvironment of coaggregates could be eval uated on the basis of isokinetic temperature (beta). On the other hand , in the stereoselective hydrolysis of dipeptide esters as mediated by cyclodextrins (CyD), a high diastereoselectivity (k(2)(DL)/k(2)(LL)=4 6) and preferential binding property (K-b(DL)/K-b(LL)=2.4) were obseve d for the hydrolysis of N-(benzyloxycarbonyl)-D (L)-phenylalanyl-L-phe nylalanine p-nitrophenyl ester (Z-D(L)-Phe-L-Phe-PNP) by gamma-CyD. Fu rthermore, the computer modeling (MOPAC calculation) study suggests th at a favorable molecular recognition between the substrate and catalys t through the effective hydrophobic interactions and hydrogen bonds sh ould be very important for the enhancement of stereoselectivity.