Recovery of doxycycline and products thereof

Claim 1

A process for the recovery of α-6-deoxy-5-hydroxytetracycline in high purity from the crude reaction mixture resulting from the conversion of an intermediate into said α-6-deoxy-5-hydroxytetracycline and having the same as well as reaction by-products, degradation products and the β-isomer as impurities, said crude reaction mixture being the initial reaction mixture in which the α-6-deoxy-5-hydroxytetracycline is present prior to the institution of any recovery procedures, which consists essentially of the steps of (1) first acidifying said crude reaction mixture with a concentrated aqueous solution of methanesulfonic acid, sulphuric acid or hydrochloric acid, (2) then heating to a temperature of 60° to 90° C until said impurities are further degraded, (3) cooling said reaction mixture and then (4) precipitating said α-6-deoxy-5-hydroxytetracycline from said reaction mixture thus treated and cooled, in the form of water insoluble acid addition salts and molecular complexes selected from the group consisting of 5-sulfosalicylate, N,N'-dibenzylethylenediamine- and N,N'-dibenzylethylenediimine molecular complexes, N,N'-dibenzylethylenediamine alkaline earth metal and, N,N'dibenzylethylenediimine alkaline earth metal molecular complexes by adding the corresponding acid or molecular complex to said treated and cooled reaction mixture, said steps (1) - (4) being carried out sequentially without any intervening steps.