Intramolecular Catalysis. IX.1Intramolecular General Base-General Acid Catalysis of Ester Solvolysis2,3

1966 ◽  
Vol 88 (2) ◽  
pp. 347-350 ◽  
Author(s):  
S. Morris Kupchan ◽  
Stuart P. Eriksen ◽  
Y.-T. S. Liaug
Keyword(s):  
Acid Catalysis ◽  
Intramolecular Catalysis ◽  
General Base ◽  
General Acid

Deuterium exchange of C-methyl protons in lumazine derivatives

1970 ◽  
Vol 48 (2) ◽  
pp. 263-270 ◽  
Author(s):  
J. M. McAndless ◽  
Ross Stewart
Keyword(s):  
Proton Magnetic Resonance ◽  
Proton Magnetic Resonance Spectroscopy ◽  
Acid Catalysis ◽  
Deuterium Exchange ◽  
Base Catalysis ◽  
Resonance Spectroscopy ◽  
Methyl Group ◽  
General Base ◽  
General Acid ◽  
Acid Catalyzed

Proton magnetic resonance spectroscopy has been used to examine the deuterium exchange of the methyl protons in two lumazine derivatives. The exchange occurs at the C-7 methyl group in 6,7,8-trimethyllumazine (2) and at the C-6 methyl group in 1,7-dihydro-6,7,8-trimethyllumazine (3). The former reaction is subject to both general acid- and general base-catalysis but the latter only to general acid-catalysis. Plausible mechanisms for the reactions of both compounds are advanced, involving in the case of 3, acid-catalyzed addition of water across the C6—N5 double bond.

Intramolecular Bifunctional General Base-General Acid-Catalysis of Ester Solvolysis

1963 ◽  
Vol 85 (3) ◽  
pp. 350-351 ◽  
Author(s):  
S. Morris. Kupchan ◽  
Stuart P. Eriksen ◽  
Yun-Teh. Shen
Keyword(s):  
Acid Catalysis ◽  
General Base ◽  
General Acid

Intramolecular amine-catalyzed ketone enolization. A search for concerted intramolecular general-base, general-acid catalysis

1969 ◽  
Vol 91 (19) ◽  
pp. 5339-5345 ◽  
Author(s):  
James K. Coward ◽  
Thomas C. Bruice
Keyword(s):  
Acid Catalysis ◽  
General Base ◽  
General Acid

scholarly journals pH-dependence and structure–activity relationships in the papain-catalysed hydrolysis of anilides

1971 ◽  
Vol 124 (1) ◽  
pp. 117-122 ◽  
Author(s):  
G. Lowe ◽  
Y. Yuthavong
Keyword(s):  
Acid Catalysis ◽  
Ph Dependence ◽  
Base Catalysis ◽  
General Base ◽  
Structure Activity ◽  
Equilibrium Binding ◽  
General Acid ◽  
Leaving Group ◽  
Hydrolysis Of ◽  
Equilibrium Binding Constant

The pH-dependence of the Michaelis–Menten parameters for the papain-catalysed hydrolysis of N-acetyl-l-phenylalanylglycine p-nitroanilide was determined. The equilibrium binding constant, Ks, is independent of pH between 3.7 and 9.3, whereas the acylation constant, k+2, shows bell-shaped pH-dependence with apparent pKa values of 4.2 and 8.2. The effect of substituents in the leaving group on the acylation constant of the papain-catalysed hydrolysis of hippuryl anilides and N-acetyl-l-phenylalanylglycine anilides gives rise in both series to a Hammett ρ value of -1.04. This indicates that the enzyme provides electrophilic, probably general-acid, catalysis, as well as the nucleophilic or general-base catalysis previously found. A mechanism involving a tetrahedral intermediate whose formation is general-base-catalysed and whose breakdown is general-acid-catalysed seems most likely. The similarity of the Hammett ρ values appears to exclude facilitated proton transfer as a means through which the specificity of papain is expressed.

General Base-General Acid-Catalysis of Ester Solvolysis

1962 ◽  
Vol 84 (21) ◽  
pp. 4159-4160 ◽  
Author(s):  
S. Morris. Kupchan ◽  
Stuart P. Eriksen ◽  
Mendel. Friedman
Keyword(s):  
Acid Catalysis ◽  
General Base ◽  
General Acid

scholarly journals THE NATURE OF GENERAL BASE-GENERAL ACID CATALYSIS IN SERINE PROTEASES

1969 ◽  
Vol 64 (4) ◽  
pp. 1335-1342 ◽  
Author(s):  
L. Polgar ◽  
M. L. Bender
Keyword(s):  
Serine Proteases ◽  
Acid Catalysis ◽  
General Base ◽  
General Acid

Intramolecular Catalysis. VIII.1General Base-General Acid Catalysis of Ester Solvolysis2,3

1966 ◽  
Vol 88 (2) ◽  
pp. 343-346 ◽  
Author(s):  
S. Morris Kupchan ◽  
Stuart P. Eriksen ◽  
Mendel Friedman
Keyword(s):  
Acid Catalysis ◽  
Intramolecular Catalysis ◽  
General Acid

Concerted general base and bifunctional general acid catalysis of the aminolysis of phenyl acetate by pyrazole

1987 ◽  
Vol 109 (19) ◽  
pp. 5790-5800 ◽  
Author(s):  
James C. Fishbein ◽  
Howard Baum ◽  
Michael M. Cox ◽  
William P. Jencks
Keyword(s):  
Acid Catalysis ◽  
Phenyl Acetate ◽  
General Base ◽  
General Acid
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