Anhydride mechanism

Oxyacids of sulphur and their anhydrides, mechanisms and reactivity in reactions of organic, 17, 65 Oxygen isotope exchange reactions of organic compounds, 3, 123... 

Add 200 g. of red lead In portions to 750 c.c. of pure glacial acetic acid + 20 c.c. of acetic anhydride mechanically stirred and kept at 65°, adding each portion only after the red colour produced by the preceding portion has disappeared. The tetra-acetate crystallises out on cooling. It can be recrystallised from glacial acetic aoid and is stable in the absence of moisture (O. Dimroth and R. Schweizer, Ber., 1923, 56, 1375). For the determination of lead tetra-acetate in solution, see R. Criegee, Ber., 1931, 64, 260. 

Orbital interactions and long-range electron transfer, 38, 1 Organic materials for second-order non-linear optics, 32, 121 Organic reactivity, electron-transfer paradigm for, 35, 193 Organic reactivity, structure determination of, 35, 67 Orotidine monophosphate decarboxylase, the mechanism of, 38, 183 Oxyacids of sulphur and their anhydrides, mechanisms and reactivity in reactions of organic, 17, 65... 

If the anhydride mechanism is correct, the water molecule bound to the Zn2+ probably provides an HCL ion necessary for the hydrolysis of the intermediate anhydride.417... 

Oxyacids of sulphur and their anhydrides, mechanisms and reactivity in reactions of... 

Circumstantial evidence against the anhydride mechanism comes from the observation of Christianson and Lipscomb (1986) that the tight-binding inhibitor [110] (Kt = 0.2 pM) binds as the hydrate, rather than as an adduct with Glu-270, as would be expected were Glu-270 a nucleophile rather than an acid/base catalyst. In the complex of carboxypeptidase and the hydrate of... 

In models for carboxypeptidase A we showed the intracomplex catalyzed hydrolysis of an ester by a metal ion and a carboxylate ion [106], which are the catalytic groups of carboxypeptidase A. Some mechanistic proposals for the action of carboxypeptidase involve an anhydride intermediate that then hydrolyzes to the product and the regenerated enzyme. Although we later found convincing evidence that the enzyme does not use the anhydride mechanism in cleaving peptides [96-99], it may well use such a mechanism with esters. In a mimic of part of this mechanism we showed [107], but see also Ref. 108, that we could achieve very rapid hydrolysis of an anhydride by bound Zn2+, which is the metal ion in the enzyme. In another model, a carboxylate ion and a phenolic hydroxyl group, which are in the enzyme active site, could cooperatively catalyze the cleavage of an amide by the anhydride mechanism [109]. 

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