Chymotrypsin-catalyzed phenyl ester hydrolysis. Evidence for electrophilic assistance on carbonyl oxygen

Biochemistry ◽  
1970 ◽  
Vol 9 (17) ◽  
pp. 3383-3390 ◽  
Author(s):  
Andrew Williams
Keyword(s):  
Carbonyl Oxygen ◽  
Ester Hydrolysis ◽  
Phenyl Ester

Carbonyl oxygen exchange of glycol monoesters. Rate and equilibrium constants for the formation of a tetrahedral intermediate

1979 ◽  
Vol 57 (12) ◽  
pp. 1531-1540 ◽  
Author(s):  
R. A. McClelland ◽  
M. Ahmad ◽  
J. Bohonek ◽  
S. Gedge
Keyword(s):  
Equilibrium Constant ◽  
Rate Constants ◽  
Equilibrium Constants ◽  
Carbonyl Oxygen ◽  
Ester Hydrolysis ◽  
Oxygen Exchange ◽  
Ortho Ester ◽  
Kinetic Investigations ◽  
Relationship Of ◽  
The Relationship

Kinetic investigations of the hydrolysis of the 2-phenyl-4,4,5,5-tetramethyl-1,3-dioxolenium ion and 2-phenyl-2-methoxy-4,4,5,5-tetramethyl-1,3-dioxolane furnish rate constants for all three reaction stages of the ortho ester hydrolysis: (1) generation of the dioxolenium ion, (2) hydration of this ion to form hydrogen ortho ester, and (3) breakdown of this species to pinacol monobenzoate. The equilibrium constant for stage (2) can also be obtained. This study complements a previous investigation of 2-phenyl-2-alkoxy-1,3-dioxolanes where similar information was obtained.The rate constants for carbonyl oxygen exchange of the ester products of these reactions, pinacol monobenzoate and ethylene glycol monobenzoate, have been measured. This reaction is shown to proceed by a different mechanism to that normally associated with exchange of carboxylic acid derivatives: cyclization of the glycol monoester to form hydrogen ortho ester, followed by loss of the labelled exocyclic OH group to give 1,3-dioxolenium ion. Reversal of these steps, initiated by an unlabelled water molecule, results in exchange. The relationship of this mechanism with that of the ortho ester hydrolysis is obvious; it is shown that the exchange provides rate constants for the reverse of stage (3). This means that both the forward and reverse rates of this process have been obtained, and this provides the equilibrium constant.

Kinetic and Theoretical Studies on the Mechanism of Intramolecular Catalysis in Phenyl Ester Hydrolysis

2006 ◽  
Vol 71 (20) ◽  
pp. 7650-7656 ◽  
Author(s):  
Gabriel O. Andrés ◽  
Adriana B. Pierini ◽  
Rita H. de Rossi
Keyword(s):  
Ester Hydrolysis ◽  
Theoretical Studies ◽  
Phenyl Ester ◽  
Intramolecular Catalysis

Dimethyl-Carbamic Acid 2,3-Bis-Dimethylcarbamoyloxy-6-(4-Ethyl-Piperazine- 1-Carbonyl)-Phenyl Ester: A Novel Multi-Target Therapeutic Approach to Neuroprotection

2010 ◽  
Vol 6 (3) ◽  
pp. 123-140 ◽  
Author(s):  
Laurent Lecanu ◽  
Laurent Tillement ◽  
Althea McCourty ◽  
Georges Rammouz ◽  
Wenguo Yao ◽  
...  
Keyword(s):  
Therapeutic Approach ◽  
Carbamic Acid ◽  
Phenyl Ester

Participation of 19-ester groups in the cleavage of 2α,3α- and 5α,6α-steroid epoxides. A case of competition between participation and external nucleophile attack

1979 ◽  
Vol 44 (5) ◽  
pp. 1496-1509 ◽  
Author(s):  
Pavel Kočovský ◽  
Václav Černý
Keyword(s):  
Perchloric Acid ◽  
Hydrobromic Acid ◽  
Ester Group ◽  
Carbonyl Oxygen ◽  
Cyclic Carbonate ◽  
Cyclic Ether ◽  
Normal Reaction ◽  
Neighboring Group ◽  
Ether Oxygen ◽  
The Difference

Acid cleavage of the acetoxy epoxide IIIa with aqueous perchloric acid or hydrobromic acid gave two types of products, i.e. the diol Va or the bromohydrin VIa, and the cyclic ether VIII. The latter compound arises by participation of ether oxygen of the ester group. On reaction with perchloric acid the epoxide IVa gave the diol XIIIa as a product of a normal reaction and the isomeric diol Xa as a product arising by intramolecular participation of the carbonyl oxygen of the 19-acetoxy group. Participation of the 19-ester group is confirmed by the formation of the cyclic carbonate XI when the 19-carbonate IVb is treated analogously. On reaction with hydrobromic acid, the epoxide IVa gave solely the bromohydrin XIVa as a product of the normal reaction course. Discussed is the similarity of these reactions with electrophilic additions to the related 19-acetoxy olefins I and II, the mechanism, the difference in behavior of both epoxides III and IV, the dependence of the product ratio on the nucleophility of the attacking species, and the competition between participation of an ambident neighboring group and an external nucleophile attack.

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