Erythromycins A through D, represented by formula (I) below,
______________________________________ ##STR3## (I) Erythromycin R.sup.a R.sup.b ______________________________________ A OH CH.sub.3 B H CH.sub. 3 C OH H D H H ______________________________________
are well-known and potent antibacterial agents. Erythromycin A in particular is widely used to treat and prevent bacterial infection. As with other antibacterials, however, bacterial strains having resistance or insufficient susceptibility to erythromycin have been identified. Another drawback of erythromycins is their poor acid stability, which sometimes results in poor or unpredictable oral absorption. Consequently, numerous investigators have sought to prepare chemical derivatives of erythromycin in an attempt to obtain analogs having modified or improved profiles of antibiotic activity.