Chemical modification of spiramycins. III. Synthesis and antibacterial activities of 4''-sulfonates and 4''-alkylethers of spiramycin I.

Among the derivatives protected with t-butyldimethylsilylether of spiramycin I, 2'-O-acetylspiramycin I 3,18-(O-t-butyldimethylsilyl)acetal was found to be a suitable intermediate for 4''-modification of spiramycin I. Seven 4''-sulfonates and four 4''-alkylethers were synthesized, which were more active against bacteria in vitro than spiramycin I. 4''-Substituted derivatives with relatively small sulfonyl and alkyl groups were comparable in therapeutic effect to spiramycin I.