Degradation of mecillinam in aqueous solution.

The hydrolysis of mecillinam in aqueous solution (37 degrees) was studied at pH 2-10. The degradation products observed by TLC and NMR were identified and quantified. Several of these compounds were synthesized. Mecillinam and the key degradation product, (6R)-6-formamidopenicillanic acid, underwent reversible 6-epimerization in basic solution. Some of the thiazolidine derivatives formed epimerized at position 2. In contrast to penicillins, the degradation pattern of mecillinam becomes more complex with increasing pH. Rate constants for some processes are given.