Catalysis of Ester Aminolysis by Cyclodextrins. The Reaction of Alkylamines with p-Nitrophenyl Alkanoates

Abstract

The effects of four cyclodextrins (alpha-CD, beta-CD, hydroxypropyl-beta-CD, and gamma-CD) on the aminolysis of p-nitrophenyl alkanoates (acetate to heptanoate) by primary amines (n-propyl to n-octyl, isobutyl, isopentyl, cyclopentyl, cyclohexyl, benzyl) in aqueous solution have been investigated. Rate constants for amine attack on the free and CD-bound esters (k(N) and k(cN)) have ratios (k(cN)/k(N)) varying from 0.08 (retardation) to 180 (catalysis). For the kinetically equivalent process of free ester reacting with CD-bound amine (k(Nc)), the ratios k(Nc)/k(N) vary from 0.2 to 28. Either way, there is evidence of catalysis in some cases and retardation in others. Changes in reactivity parameters with structure indicate more than one mode of transition state binding to the CDs. Short esters react with short alkylamines by attack of free amine on the ester bound by its aryl group, but for longer amines, free ester reacts with CD-bound amine. Reaction of long esters with long amines, which is catalyzed by beta-CD and gamma-CD, involves inclusion of the alkylamino group and possibly the ester acyl group. The larger cavity of gamma-CD may allow the inclusion of the ester aryl group, as well as the alkylamino group, in the transition state. Reaction between an ester bound to the CD by its acyl group and free amine appears not to be important.

Factors controlling flavors binding constants to cyclodextrins and their applications in foods

“…Several classes of compounds, that can form inclusion complexes with natural cyclodextrin, have been subjected to systematic studies. These cover almost every class of compounds such aliphatic alcohols (Cabaleiro-Lago, García-Río et al, 2005), amines and acids (Gadosy, Boyd, & Tee, 2000), aminoacids (Tee, Gadosy, & Giorgi, 1997), ketones (Iglesias, 2003), surfactants (Dorrego et al, 2000;Fernández et al, 2000;Garcia-Rio et al, 2004) and other compounds Rekharsky & Inoue, 1998).…”

In Vivo Assay Reveals Microbial OleA Thiolases Initiating Hydrocarbon and β-Lactone Biosynthesis

“…On the basis of published reports (24-26), we expected that the long-chain p-nitrophenyl acyl esters would generally not enter E. coli cells without a permeabilizing agent. Following the general protocol for a highthroughput assay for oxygenases that used p-nitrophenyl ethers, polymyxin B sulfate was used as an E. coli cell permeabilizer (24,25,27). With this additive, rates for hydrolysis of C 4 to C 16 chain length p-nitrophenyl esters were significantly higher than the background, allowing a determination of OleA activity (Fig.…”

Stabilization of the pesticide Fenitrothion towardOandNnucleophiles in the presence of cyclodextrins

“…Considering that Pip forms inclusion complexes with CDs, the nucleophilic attack to organic substrates in the presence of CD may take place by different pathways. In the case of Fenitrothion and an amine (A) as Pip, these reactions are as follows: (i) the free 1 with the free amine; (ii) the free amine with the complexed 1 ; (iii) the complexed amine with the free 1 ; and (iv) the complexed amine with the complexed 1 (each of them complexed by one CD) . Figure illustrates the possible reactions of 1 when the amine is Pip with its second‐order rate constant expression, respectively.…”

“…In the case of Fenitrothion and an amine (A) as Pip, these reactions are as follows: (i) the free 1 with the free amine; (ii) the free amine with the complexed 1; (iii) the complexed amine with the free 1; [27][28][29] and (iv) the complexed amine with the complexed 1(each of them complexed by one CD).…”