Rate and enantioselectivity with complexes of activated substrates and simply modified cyclodextrins

Abstract

The rate of hydrolytic cleavage of a number of enantiomeric activated substrates, nitrophenyl esters or carbonates, was measured in the presence of some modified β-cyclodextrins: heptakis-[6-deoxy-6-(N-methylacetamido)]cyclohepta-amylose (9), heptakis-(2,6-di-O-methyl)cyclohepta-amylose (10), and heptakis-(2,3,6-tri-O-methyl)cyclohepta-amylose (11). In the presence of (9) the rate enhancements were considerably larger and enantioselectivities only slightly smaller than those observed with native β-cyclodextrin. With (10) and (11) inhibition was observed, the effects being substantially larger in the case of (10) than in that of the permethylated cyclodextrin (11), and enantioselectivity was virtually absent.