Alfa Farmaceutici S.p.a.

Lauretta Montecchi

Egidio Marchi

New rifamicyn derivatives of the following general formula ##STR1## wherein: A may be the structure ##STR2## --x-- is a chemical bond or nil; R is hydrogen or acetyl

Imidazo-rifamycin derivatives with antibacterial utility

8-amino and 8-iminorifamycins S and SV are prepared by reacting 8-methoxyrifamycin S with ammonia in an inert polar and hydrophillic solvent, converting the 8-iminorifamycin S into 8 aminorifamycin S by reaction with ammonium hydroxide in a mixture of chloroform and methanol and, if so desired, reducing the S forms to SV forms by reduction.

Rifamycin derivatives and process for their preparation

A process is disclosed for the preparation of 3 iodo-3 bromorifamycin S which consists in reacting rifamycin S with at least 2 equivalents of the corresponding halogen in the presence of at least one mole of pyridine for each equivalent of halogen. The reaction is carried out in inert, polar, hydrofillic solvents at a temperature not above the room temperature. The yields are very high and the products obtained have a high degree of purity.

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Casalecchio Di Reno, Italy

Lauretta Montecchi