55232-59-2Relevant articles and documents
Participation of two carboxyl groups in phosphodiester hydrolysis. 2. A kinetic, isotopic, and 31P NMR study of the hydrolysis of a phosphodiester with carboxyl groups fixed in an attack conformation
Bruice, Thomas C.,Blaskó, Andrei,Arasasingham, Ramesh D.,Kim, Jang-Seob
, p. 12070 - 12077 (1995)
The phosphodiesters of 4,4′-methylenebis(3-hydroxy-2-naphthoic acid) (4) and 3-carboxy-2,2′-dihydroxydiphenylmethane (5) are constrained into a cyclic structure such that the oxygens of the two o-carboxy groups of 4 and the single o-carboxy group of 5 have restricted stereospecific positions with an o-CO2- oxygen to phosphorus distance of 3.7 ?. In the hydrolysis of 4, 31P NMR and HPLC data show the existence of an intermediate cyclic acyl phosphate in the g,g conformation. The 18O isotopic effects on 31P chemical shifts show incorporation of two 18O atoms in the product H3PO4. This observation is consistent with intramolecular o-CO2- nucleophilic attack on phosphorus to provide an acyl phosphate intermediate which undergoes hydrolytic cleavage by HO-/H18O- attack on phosphorus {one 18O incorporation} to provide a phosphate monoester which also undergoes hydrolysis with a second 18O incorporation on phosphorus. For hydrolysis of 4, the pH vs log kobsd profile, the values of the deuterium solvent kinetic isotope effect, and the activation entropy accord a mechanism which involves intramolecular attack of o-CO2- on the phosphate phosphorus assisted by the o-CO2H as a general acid catalyst. The latter can involve o-CO2H hydrogen bonding to the -(PO2-)- oxygen(s) and/or leaving phenolic oxygen. At neutrality, 4 hydrolyzes ca. 104 fold faster than 5 which only has one o-carboxy group and 108-109-fold faster than diphenyl phosphate.
