Enantioselectivity effects in the hydrolytic cleavage of activated substrates with α- and β-cyclodextrins

Abstract

The kinetics of hydrolytic cleavage of the enantiomers of p- and m-nitrophenyl (Np) phenylacetate esters of general structure PhCR¹R²–CO₂–Np where R¹,R²= H,Me [(1), (2)], H,OMe [(3), (4)], or CF₃,OMe [(5), (6)], and of the carbonates PhCHMe–OCO₂–p-Np (7) and n-C₆H₁₃–CHMe–OCO₂–p-Np (8), have been measured in the presence of α- and β-cyclodextrins. The rates of intracomplex cleavage were found to be larger for the R- than for the S-enantiomers in almost all cases; the enantioselectivity factors range from unity to ca. 19 depending on the relative size of the pairs of substituents R¹ and R². The effects have been interpreted with the help of molecular models.