| 摘要 |
<p>1386662 Bromo-tetracycline derivatives PLIVA PHARMACEUTICAL & CHEMICAL WORKS 5 April 1972 [5 April 1971] 15688/72 Heading C2C 6 - Demethyl - 6 - deoxy - 6 - methylene - 11α-bromo-tetracyclines (III) and 9-bromo-anhydrotetracyclines (IV) are prepared according to the following reaction sequence, wherein R represents -H or -OH In the reaction sequence, tetracycline (I, R = H) or oxytetracycline (I, R = OH) is reacted with bromine in the presence of pyridine or morpholine to give an 11a-bromo-tetracycline- 6,12-hemiketal (II). The latter is then dehydrated with either a mixture of sulphuric acid and acetonitrile resulting in the 6-demethyl-6- deoxy - 6 - methylene - 11a - bromo - tetracycline (III), or a mixture of sulphuric acid and glacial acetic acid resulting in the 9-bromoanhydrotetracycline (IV). When sulphuric acid alone or containing 30% water is used, a mixture of (III) and (IV) are obtained, the proportion of the anhydro-derivative IV increasing with the concentration of the sulphuric acid. In a comparative example, tetracycline is brominated to 11a-bromotetracycline-6,12-hemiketal with N-bromosuccinimide.</p> |
