L-aspartate of erythromycin A cyclic 11,12-carbonate, a new semisynthetic erythromycin derivative.

Erythromycin A cyclic 11,12-carbonate, a compound with high antibacterial activity, forms with L-aspartic acid a salt possessing valuable properties as a potential chemotherapeutic agent. The L-aspartate of erythromycin A cyclic 11,12-carbonate exhibits strong anti-bacterial activity, especially against Gram-positive bacteria and shows low toxicity. The serum and the lung tissue levels of the discussed salt after a single dose administration to a rat were measured in comparison with those of erythromycin, its L-aspartate, erythromycin cyclic 11,12-carbonate and its L-glutamate. The new erythromycin derivative showed definitely superior characteristics to those of the other substances tested. The activity of the L-aspartate of erythromycin A cyclic 11,12-carbonate in chemotherapy of experimental staphylococcal infection and experimental pneumococcal bronchopneumonia in mice is superior to that of the parent carbonate and erythromycin itself.