Abstract: A process for the hydrogenation of a 6-methylenetetracycline in the production of alpha-6-deoxytetracycline, particularly the antibiotic doxycycline, in the presence of a transition metal complex of the formula MCl.sub.x (PPh.sub.3).sub.y wherein M is Cu, Co or Ni, x is 1 or 2 and y is 1-3, and a trace of rhodium either as the supported metal or as a rhodium salt, as a hydrogenation catalyst. The desired alpha-6-deoxytetracycline product is produced in high yields and stereospecificities. The process requires the use of substantially cheaper transition metal complexes and only traces of rhodium in the hydrogenation catalyst per mole of the 6-methylene tetracycline hydrogenated.

Abstract: A coordination compound useful as a hydrogenation catalyst, having the formula: ##STR1## wherein Ph is phenyl; R is hydrogen or C.sub.1 -C.sub.4 alkyl; and X is chloro, bromo or iodo. This compound is particularly useful as a homogeneous hydrogenation catalyst in the production of alpha-6-deoxytetracyclines, particularly the antibiotic doxycycline. The desired alpha-6-deoxy product is produced in high yields and stereospecificities, the process requiring the use of minimal quantities of rhodium metal in the hydrogenation catalyst per mole of the 6-methylenetetracycline hydrogenated.

Abstract: A coordination compound useful as a hydrogenation catalyst, having the formula: ##STR1## wherein Ph is phenyl; R is hydrogen or C.sub.1 -C.sub.4 alkyl; and X is chloro, bromo or iodo. This compound is particularly useful as a homogeneous hydrogenation catalyst in the production of alpha-6-deoxytetracyclines, particularly the antibiotic doxycycline. The desired alpha-6-deoxy product is produced in high yields and stereospecificities, the process requiring the use of minimal quantities of rhodium metal in the hydrogenation catalyst per mole of the 6-methylenetetracycline hydrogenated.

Abstract: A process for the hydrogenation of a 6-methylenetetracycline in the production of alpha-6-deoxytetracyclines, particularly the antibiotic doxycycline, in the presence of hydriodotetrakis (triphenylphosphine) rhodium (I) as a homogenous hydrogenation catalyst. The desired alpha-6-deoxy product is produced in high yields and stereospecificities, the process requiring the use of minimal quantities of rhodium metal in the hydrogenation catalyst per mole of the 6-methylenetetracycline hydrogenated.

Abstract: A coordination compound useful as a hydrogenation catalyst, having the formula: ##STR1## wherein Ph is phenyl; R is hydrogen or C.sub.1 -C.sub.4 alkyl; and X is chloro, bromo or iodo. This compound is particularly useful as a homogeneous hydrogenation catalyst in the production of alpha-6-deoxytetracyclines, particularly the antibiotic doxycycline. The desired alpha-6-deoxy product is produced in high yields and stereospecificities, the process requiring the use of minimal quantities of rhodium metal in the hydrogenation catalyst per mole of the 6-methylenetetracycline hydrogenated.