Year-end Sale % OFF 
Abstract
The reactions of p-nitrophenyl acetate, 1, with both enantiomers of the following α-amino acids: alanine (2a), methionine (2b), leucine (2c), and tryptophan (2d), were studied in the presence of p-cyclodextrin (β-CD). All the reactions were catalyzed by β-CD and no chiral discrimination was observed. The reactions of 1 with the D isomers of 2a and 2d were also studied in the presence of α- and γ-CD. In both cases the catalysis increased in the order α < γ < β-CD. Also, to analyze the influence of the polar nature of the nucleophile, the reactions of 1 with both enantiomers of the methyl esters of 2a, 2c, and 2d were studied in the presence of β-CD. The catalysis observed was significantly smaller than that for the reactions with the amino acids. It is suggested that the catalysis by CDs is due to the formation of a ternary hydrogen-bonding complex that results from the association of the amino acid with the complexed substrate. The effect of the size of the CD cavity on the observed catalysis is attributed to the geometrical requirements for the reaction. The decrease in catalysis in the reactions with the methyl esters is due to a weaker hydrogen-bonding association with these neutral nucleophiles. Key words: cyclodextrins, catalysis, ester aminolysis.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
