Abstract: A process is provided for preparing alpha-6-deoxytetracyclines depicted by the formula: ##STR1## wherein Y is H, F, Cl, Br or I; and R is H, OH or --O--CO--(C.sub.1-6 alkyl);which comprises: contacting a 6-demethyl-6-deoxy-6-methylene tetracycline or salt thereof having the formula ##STR2## in which Y and R are as given above, with hydrogen at a temperature of between 15.degree. C. and 80.degree. C. in the presence of a catalyst soluble in a polar solvent, said catalyst being a complex of rhodium with electron donor ligands of a tertiary phosphine selected from the group consisting of triphenylphosphine, tributylphosphine, triethylphosphine, diethylphenylphosphine and diphenylethylphosphine and said polar solvent being a mono- or polyhydric alcohol with from 1 to 4 carbon atoms, N,N-dimethylformamide, N,N-dimethylacetamide, dioxan, tetrahydrofuran, methoxyethanol, ethoxyethanol, acetonitrile or pyridine.

Abstract: This invention relates to a novel water soluble derivatives of 6-deoxy-tetracyclines, particularly of doxycycline, in which a methionine group is linked to the tetracycline group through a methylene bridge, thus obtaining a derivative which is not only water soluble at neutral pH, but also endowed with outstanding properties from the point of view of the therapeutical use.

Abstract: This invention relates to a process for the preparation of .alpha.-6-deoxytetracyclines, by the simultaneous reductive dehalogenation and reduction by hydrogen, in a polar solvent of the corresponding 11a-halo-6-demethyl-6-deoxy-6-methylene-tetracycline, in presence of a suitable member of the group of the tertiary phosphines, arsines and stibines, as regards the dehalogenation and of a catalyst, selected from amongst the complexes of noble metals with electron-donor ligands, soluble in the reaction medium, whereby the reaction is carried out according to the mechanism of the homogeneous catalysis.

Abstract: The invention relates to the preparation of 6-demethyl-6-deoxy-6-methylene-tetracycline by means of reductive dehalogenation of the corresponding 11a-halo-6-demethyl-6-deoxy-6-methylene-tetracycline, the reaction being carried out in presence of the stoichiometric quantity of a tertiary phosphine, arsine or stibine and in a polar solvent. The time and temperature of the reaction are controlled within specified limits to obtain a complete conversion.