COMPLEX OF 7-DIMETHYLAMINO-6-DEMETHYL-6-DEOXYTETRACYCLINE HYDROCHLORIDE

1382766 Purifying 7-dimethylamino-6-demethyl-6-deoxytetracycline AMERICAN CYANAMID CO 13 Feb 1973 [11 May 1972] 7044/73 Heading C2C The invention comprises (i) a novel complex of minocycline hydrochloride (i.e. 7-dimethylamino - 6 - demethyl - 6 -deoxytetracycline hydrochloride) and calcium chloride, having the formula wherein n is an integer from 7 to 13; and (ii) a process for purifying minocycline hydrochloride by reacting it in aqueous solution with calcium chloride in a ratio of 0À3 to 1À2 moles of calcium chloride per mole of minocycline hydrochloride at a pH of 3À1 to 4À2 to precipitate the aforesaid complex, separating the complex from the solution and regenerating the minocycline hydrochloride by subjecting the complex to a metathesis reaction. The formation of the complex is preferably effected in the presence of 15-20% w/v. of an ionizable chloride salt (e.g. NaCl) which depresses the solubility of the complex and improves its yield. The metathesis reaction employs an acid forming an insoluble calcium salt (e.g. oxalic, lauric, palmitic, hydrofluoric or tartaric acid), which is removed to leave the purified minocycline solution. Reference has been directed by the Comptroller to Specification 1,003,474.