Novel rifamycins. III. Synthesis and antibacterial activity of 3-amidino- and of 4-aminoimidazolo[4,5-c]rifamycin derivatives.

A number of semisynthetic rifamycin derivatives modified at position 3 and/or 4, belonging to general structures 2 and 4 (see Scheme 1), have been obtained. The synthesis and the biological activities of the new compounds are described. Compounds 4p and 4q display very good antimycobacterial activity in mice.