Structure activity relationships of spiramycins.

Sixty-six derivatives of spiramycin I and neospiramycin I were synthesized and evaluated by four parameters, MIC, affinity to ribosomes (ID50), therapeutic effect in mice and retention time in HPLC. Among the derivatives, 3,3'',4''-tri-O-propionyl- and 3,4''-di-O-acetyl-3''-O-butyrylspiramycin I showed the highest therapeutic effect which was superior to acetylspiramycin. Structure activity relationships of spiramycins are discussed.