Novel rifamycin derivatives of formula I (both hydroquinone and
corresponding quinone (C.sub.1-C.sub.4) forms): ##STR00001## or their
salts, hydrates or prodrugs thereof, wherein: a preferred R comprises
hydrogen, acetyl; L is a linker, a preferred linker group elements
selected from any combination of 1 to 5 groups shown FIG. 1, provided L
is not ##STR00002## wherein R.sub.1 is H, methyl or alkyl. The inventive
compounds exhibit valuable antibiotic properties. Formulations having
these compounds can be used in the control or prevention of infectious
diseases in mammals, both humans and non-humans. In particular, the
compounds exhibit a pronounced antibacterial activity, even against
multiresistant strains of microbes.