Alfa Farmaceutici S.p.a.

Gian F Tamagnone

Vincenzo Cannata

A new process for the synthesis of pyrido-imidazo-rifamycins of formula ##STR1## wherein R is hydrogen or acetyl, R.sub.1 and R.sub.2 independently represent hydrogen, (C.sub.1-4)-alkyl, benzyloxy, mono- or di-(C.sub.1-3)-alkylamino-(C.sub.1-4)-alkyl, (C.sub.1-3)-alkoxy-(C.sub.1-4)-alkyl, hydroxymethyl, hydroxy-(C.sub.2-4)-alkyl, cyano, halogen, nitro, mercapto, (C.sub.1-4)-alkylthio, phenylthio, carbamoyl, mono- or di-(C.sub.1-4)-alkyl-carbamoyl, or R.sub.1 and R.sub.2 taken together with two consecutive carbon atoms of the pyridine nucleus form a benzene ring optionally substituted by one or two methyl or ethyl groups. The process comprises reacting the rifamycin O of formula ##STR2## with a 2-aminopyridine of formula ##STR3## wherein R.sub.1 and R.sub.2 have the same meanings as before.

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Casalecchio di Reno, Italy

Gian F Tamagnone