(Ph3P)2Rh(OMe)NHNH2 is prepd. as a stereospecific catalyst for the hydrogenation of 6-demethyl-6-deoxy-6-methylene-5-hydroxytetracycline (I) into doxycycline. Thus, the catalyst was prepd. by refluxing .48 g (Ph3P)3RdCl with 76 .mu.L H2NNH2 in 20 mL MeOH for 90 min. I.HCl (7.38 g), 25 mg catalyst, and 0.1 g Ph3P in 40 mL MeOH were hydrogenated at 89.degree. and 8 kg/cm2, for 5.5 h to give doxycycline, isolated as the p-toluenesulfonate, in 99.5% purity.