Chemical modification of erythromycin: synthesis and preliminary bioactivity of selected amides and esters

Enhancement of the properties of a drug by mono-deuteriation: reduction of acid-catalysed formation of a gut-motilide enol ether from 8-deuterio-erythromycin B

An efficient synthesis of 8-d-erythromycin B was achieved. A deuterium isotope effect suppresses formation of the corresponding enol ether, which may result in reduced gut-motilide effects.

Mechanism for the degradation of erythromycin A and erythromycin A 2'-ethyl succinate in acidic aqueous solution

A major drawback of the antibiotic erythromycin A is its extreme acid sensitivity, leading to rapid inactivation in the stomach. The accepted model for degradation in aqueous acidic solution has erythromycin A in equilibrium with erythromycin A enol ether and degrading to anhydroerythromycin A. We report a detailed kinetic study of the acidic degradation of erythromycin A and of erythromycin A 2'-ethyl succinate (the market-leading pediatric prodrug), investigating the reaction rates and degradation products via NMR. This reveals that the accepted mechanism is incorrect and that both the enol ether and the anhydride are in equilibrium with the parent erythromycin. By implication, both the anhydride and enol ether are antibacterially inactive reservoirs for the parent erythromycin. The actual degradation pathway is the slow loss of cladinose from erythromycin A (or erythromycin A 2'-ethyl succinate), which is reported here for the first time in a kinetic study. The kinetic analysis is based on global, nonlinear, simultaneous least-squares fitting of time course concentrations for all species across multiple datasets to integrated rate expressions, to provide robust estimates of the rate constants.

Pediatric Erythromycins: a Comparison of the Properties of Erythromycins A and B 2‘-Ethyl Succinates

The antibiotic erythromycin A is generally administered to children as a suspension of the pro-drug erythromycin A 2'-ethyl succinate. The success of the pro-drug depends on (a) elimination of the unacceptably bitter taste of free erythromycin, (b) its stability against stomach acid, and (c) its smooth (base-catalyzed) hydrolysis in the body to yield active erythromycin. We have investigated the rates and pathways of acid-catalyzed degradation and base-catalyzed hydrolysis of the 2'-ethyl succinates of erythromycins A and B. Esterification does not protect the drugs against acid-catalyzed degradation in solution; however, erythromycin B 2'-ethyl succinate is much more stable than the corresponding erythromycin A ester, degrading nearly 40 times more slowly. The rates of base-catalyzed hydrolysis in conditions mimicking the blood stream are similar for the two pro-drugs. We conclude that erythromycin B 2'-ethyl succinate is an attractive prospect as a pediatric erythromycin pro-drug.