| abstract |
A process for the preparation of alpha -6-deoxy-tetracyclines by the stereoselective heterogeneous hydrogenation of a 6-demethyl-6-deoxy-6-methylene-tetracycline or an acid addition salt thereof, in the presence of a tertiary phosphine, or the simultaneous dehalogenation and stereo-selective heterogeneous hydrogenation of an 11a-halo-6-demethyl-6-deoxy-6-methylene-tetracycline or an acid addition salt thereof, in the presence of a tertiary phosphine, characterized by the use of a rhodium salt catalysts, wherein the rhodium is bonded to a polysiloxane carrier, having the following formulae: Rh Cl3[N{(CH2)3 SiO3/2}3]10 Rh Cl3[N{(CH2)3 SiO3/2}3]12 Rh Cl3[N{(CH2)3 SiO3/2}3]15 Rh Cl3[HN{(CH2)3 SiO3/2}2]4 Rh Cl3[HN{(CH2)3 SiO3/2}2]8 permitting easy recovery of the rhodium, by simple filtration. |