Studies on Orally Active Cephalosporin Esters. II. : Chemical Stability of Pivaloyloxymethyl Esters in Phosphate Buffer Solution

概要

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The degradation kinetics of pivaloyloxymethyl (POM) esters of cephalosporins in phosphate buffer solution (pH6-8) were investigated. The degradation of the starting Δ^3 cephalosporin ester proceeded mainly via isomerization to the Δ^2 ester and subsequent hydrolysis to the Δ^2 acid. Hydrolysis to the Δ^3 acid (the parent acid) was very slow. Analysis of the rate constants indicated that the isomerization rate k_<12> was approximately equal to the apparent degradation rate of the Δ^3 ester k_<deg>, and slower than the hydrolysis rate of the Δ^2 ester k_<24>. The isomerization process to the Δ^2 ester was found to be the rate-determining step in the degradation of cephalosporin esters. The substituent at the C-3 position of the cephalosporins affected the degradation kinetics. The degradation was accelerated by increase of pH, buffer concentartion and added protein.
公益社団法人日本薬学会の論文
1989-09-25