Cyclodextrin-mediated deacylation of amino acid esters with marked stereoselectivity.

With respect to the hydrolysis (deacylation) of Z-D(L)-amino acid esters (N-(benzyloxycarbonyl)-D(L)-amino acid p-nitrophenyl esters) mediated by alpha-, beta- and gamma-cyclodextrins (CyDs), a remarkably high enantioselectivity (L/D=9.0) was observed for the deacylation of Ala substrate with gamma-CyD. The kinetic results on the basis of the Michaelis-Menten principle indicate that the enantioselectivity should be mainly originated in the deacylation process of substrates following the formation of gamma-CyD-substrate (1 : 1) complexes. The computer modeling (molecular mechanics) studies on the inclusion complexes are also described.