Complexes of tetracyclines with N,N'-dibenzylideneethylenediimine and alkaline earth ions
In the production of tetracyclines it is possible to eliminate the org. solvents, increase the yields, and shorten the manufg. process by formation of complexes including tetracyclines, alk.-earth ions and N,N'-dibenzylideneethylenediamine (I). The sp. rotations and uv and ir data for these complexes are reported. The addn. of I to the culture medium during the fermentation is followed by the adjustment of pH at the end of fermentation; the broth is then filtered and pH corrected again with NH4OH or alk. earth hydroxides. Further amts. of I are added up to 0.5 mole per mole of tetracycline, oxytetracycline, chlortetracycline, and 1.5 mole per mole of demethylchlortetracycline. The broth is then treated with addnl. base until the pH is 8-9.5 and the complex (II) ppts. By acidification with HCl of an aq. suspension of II, it is possible to obtain the pure base of the tetracycline involved when its isolelec. point is reached. For example, a fermentation medium contg. starch, corn steep liquor, CaCO3, (NH4)2SO4, NH4Cl, and Cu, Fe, or Zn sulfates is inoculated with Streptomyces alboflavus and then 400 mg. of I/l. is added after 0, 36, 72, and 96 hrs. of fermentation. After 150 hrs., fermentation is stopped when the concn. of oxytetracycline is 7.6 g./l., H2SO4 (25%) is added to the broth until the pH is 1.5, and then mycelium removed by filtration; by treatment with 12% NH4OH, the pH is adjusted to 6, then 140 g. I is added and more 12% NH4OH until the pH reaches 9.5. After stirring for 3 hrs. and filtering, the solid complex, I-tetra-Ca oxytetracycline, is washed several times and then suspended in H2O. The suspension is treated with 10% oxalic acid until the pH is 1.5. Then the soln. is filtered and, when its pH is adjusted to 5, the pure oxytetracycline base is sepd. by crystn. The yield is 87%.