Stereoselective inhibition of butyrylcholinesterase by enantiomers of exo- and endo-2-norbornyl-N-n-butylcarbamates

Abstract

Enantiomers of exo- and endo-2-norbornyl-N-n-butylcarbamates were characterized as pseudo substrate inhibitors of butyrylcholinesterase. These inhibitions discriminate enantiomers of the inhibitors and therefore show stereoselectivity for the enzyme. For inhibitions by (R)-(+)- and (S)-(-)-exo-2-norbornyl-N-n-butylcarbamates, R-enantiomer is a more potent inhibitor than S-enantiomer. But, for inhibitions by (R)-(+)- and (S)-(-)-endo-2-norbornyl-N-n-butylcarbamates, S-enantiomer is a more potent inhibitor than R-enantiomer. Optically pure (R)-(+)-exo-, (S)-(-)-exo-, (R)-(+)-endo-, and (S)-(-)-endo-2-norbornyl-N-n-butylcarbamates were synthesized from condensations of optically pure (R)-(+)-exo-, (S)-(-)-exo-, (R)-(+)-endo-, and (S)-(-)-endo-2-norborneols with n-butyl isocyanate, respectively. Optically pure norborneols were obtained from kinetic resolution of their racemic esters by lipase catalysis in organic solvent.