| 摘要 |
Hydrogenation of the exocyclic methylene gp. of a 6-deoxy-6-demethyl-6-methylene-tetracycline (I), or its acid addition salt, in a stereoselective manner giving the alpha-isomer in preference to the beta-isomer, is carried out at 20-100 degrees C and 1-100 atmos. under neutral conditions, or using a weakly acidic acid addn. salt, in the presence of a catalytic amt. of a cpd. of formula Rh(OCOR)2(P C6H5 3) (II) (where R = H, 1-6C alkyl, ClCH2, Cl2CH, Cl3C, FCH2, F2CH, F3C, phenyl, chlorphenyl, tolyl, anisyl). The ratio of alpha-isomer to beta-isomer is >=9:1. Known methods give a less favourable ratio e.g. 1:1. |
