3101-11-9Relevant academic research and scientific papers
Cyclodextrin trimers as receptors for arranging ester and catalyst at optimized location to achieve enhancement of hydrolytic activity
Nakajima, Hiroki,Sakabe, Yuzuru,Ikeda, Hiroshi,Ueno, Akihiko
, p. 1783 - 1786 (2004)
Two novel trimer receptor molecules (AC and AD trimers) consisting of two α-cyclodextrins (α-CDs) and one β-cyclodextrin (β-CD) have been designed and synthesized in order to make an optimum arrangement between a substrate and a catalyst. In the reaction
Synthesis and optimization of tri(propylene glycol) glycerolate diacrylate cross-linked polystyrene resin in polypeptide synthesis: Role of the macromolecular support in solid phase peptide synthesis
Sasikmnar,Kumar,Arnnan,Rajasekharaa Pillai
, p. 2886 - 2895 (2002)
A novel tri(propylene glycol) glycerolate diacrylate cross-linked polystyrene support for solid phase peptide synthesis was prepared by aqueous radical suspension polymerization. The peptides were grown from the hydroxy functionality of the cross-linker i
Rate-Controlling Step of Oxazolinone Formation. Secondary and Solvent Kinetic Isotope Effects
Matta, Michael S.,Andracki, Mark E.
, p. 6036 - 6039 (2007/10/02)
The β-deuterium secondary kinetic isotope effect for the formation of 2-phenyloxazolin-5-one in the alkaline hydrolysis of p-nitrophenyl n-benzoylglycinate (p-NO2C6H4O2CCL2NHOCC6H5, L = H or D) was determined to be kH/kD = 1.03 +/- 0.0.2 at temperatures between 10.5 and 40.0 deg C; activation parameters for the protium ester are ΔH(excit.) = 21.7 +/- 0.4 kcal mol-1 and ΔS(excit.)298 = 31.9 +/- 0.6 cal deg-1mol-1.These results, combined with those of previous studies, suggest that leaving-group expulsion is the only step contributing to rate limitation for conversion of the glycinate to the oxazolinone.The small, normal sec ondary isotope effect probably has complex origins, which may include relief of steric strain upon cyclization and hyperconjugative stabilization of the rate-controlling transition state.Apparent second-order rate constants for the formation of 2-phenyloxazolin-5-one in the alkaline hydrolysis of the isotopically unsubstituted ester were also obtained in aqueous solvent containing various mole fraction n of D2O (kn).The kinetic solvent effects (KSIE's) are inverse at all values of n with k1.0/k0 = 1.75.Analysis of the bowl-shaped plot of k1.0/k0 vs. n indicates that fractionation of the reactant lyoxide ion in the mixed isotopic waters predominates the KSIE.A small, normal transition-state effect of about 1.3 makes the KSIE less inverse than would be expected if the entire effect originated in lyoxide fractionation.
Acylaminoacetyl Derivatives of Active Methylene Compounds. 1. The Cyclization of the Benzoylaminoacetyl Derivatives to α-Substituted Tetramic Acids (1)
Igglessi-Markopoulou, Olga,Sandris, Constantine
, p. 883 - 890 (2007/10/02)
Hippuric acid was converted to α-Y-substituted tetramic acids (Y = -CN, -CO2R and -COCH3) according to the following general scheme of reactions: a) preparation of the hippuric acid chloride or of its p-nitrophenyl ester; b) C-acylation of an active methy
Structure-Reactivity Studies on the Equilibrium Reaction between Phenolate Ions and 2-Aryloxazolin-5-ones: Data Consistent with a Concerted Acyl-Group-Transfer Mechanism
Curran, Terence C,Farrar, Charles R.,Niazy, Omima,Williams, Andrew
, p. 6828 - 6837 (2007/10/02)
The rate and equilibrium constants for the reaction between phenolate anions and 2-aryloxazolin-5-ones have been measured as a function of the structures Ar and Ar'.The change in "effective" charge on both phenol-leaving oxygen and endocyclic oxygen from ground to transition state, as determined from the relevant Broensted parameters, is substantial and essentially additive consistent with a concerted displacement mechanism.The stepwise mechanism requires a small change in effective charge on the phenol oxygen because departure of phenolate ion from the tetrahedral intermediate cannot be rate limiting.Hydroxide ion attack on the C-5 atom of the oxazolinone to yield a benzoylglycine has a Hammett ?- dependence which can only arise from a concerted displacement; the rate-limiting step for the stepwise mechanism is the addition of hydroxide and the transition state of the rate-limiting step will therefore not involve much endocyclic C-O bond fission.An inverse deuterium oxide solvent isotope effect indicates that the observed general-acid catalysis has a specific-acid/nucleophilic mechanism; both hydroxide and oxonium ion catalysis are demonstrated by using 18O-labeling experiments to involve nucleophilic attack at the carbonyl (C-5) center.The equilibrium constant for reaction of azide ion with 2-phenyloxazolin-5-ones has been measured; it is suggested that the absence of racemization during azide coupling in peptide synthesis is related to the very unfavorable equilibrium constant for oxazolinone formation compared with that of activated oxygen esters.
The Mechanism of Hydrolysis and Ethylaminolysis of N-Benzoylglycine and N-Benzoylsarcosine Esters
Farrar, Charles R.,Williams, Andrew
, p. 181 - 187 (2007/10/02)
The hydrolysis and ethylaminolysis of N-benzoylglycine and N-benzoylsarcosine esters have been studied for a range of leaving hydroxy-functions with pKa from 5.45 to 15.5.Ethylaminolysis of N-benzoylglycinate esters involves kinetic terms in E
