US3637654A - Purification of erythromycin thiocyanate - Google Patents

Abstract

ERYTHROMYCIN THIOCYANATE CAN BE PURIFIED EFFECTIVELY AND ITS POTENCY CAN BE INCREASED SIGNIFICANTLY BY TREATING IT WITH TRICHLOROETHYLENE.

Description

United States Patent 6 3,637,654 PURIFICATION OF ERYTHROMYCIN THIQCYANATE Gerald George Post, Kenosha County, Wis., assiguor to Abbott Laboratories, North Chicago, Ill. No Drawing. Filed Apr. 3, 1969, Ser. No. 813,327 Int. Cl. C07c 47/18 US. Cl. 260-210 E 4 Claims ABSTRACT OF THE DISCLOSURE Erythromycin thiocyanate can be purified effectively and its potency can be increased significantly by treating it with trichloroethylene.

Erythromycin thiocyanate is prepared from erythromycin which, in turn, is prepared by fermentation and subsequent extraction. Unfortunately, the extraction methods most practical and most commonly used produce an erythromycin solution which contains a minor amount of fats and oils. These fats and oils find their way into erythromycin thiocyanate from where they cannot be easily removed.

Erythromycin thiocyanate is used as an antibiotic and, in larger amounts, for the preparation of erythromycin base from which various medicinal preparations are made, for instance erythromycin ethylsuccinate. Thus, large quantities of erythromycin thiocyanate are produced continuously and unless a substantially pure material is available, it cannot be used in the medicinal field. Furthermore, standard processes for the transformation of erythromycin thiocyanate to erythromycin base do not always remove all the fats or oils which sometimes accompany the thiocyanate so that special procedures have to be followed subsequently for their removal.

It is therefore an object of the present invention to provide a method for the purification of erythromycin thiocyanate; it is a further object of this invention to provide a simple, inexpensive and fast purification method for erythromycin thiocyanate; it is another object of this invention to provide a method for the removal of fats and oils from erythromycin thiocyanate.

These and other objects are accomplished by slurrying one part by weight of erythromycin thiocyanate in at least two parts by volume of trichloroethylene for a period sufficiently long to provide intimate contact between the liquid phase and the solid phase, and recovering the erythromycin thiocyanate from the slurry. Intimate contact between trichloroethylene and erythromycin thiocyanate can be provided by a number of known means, for instance, the erythromycin salt can be contacted with said solvent in a shaking apparatus or by stirring where batch operation is desired; however, since the necessary contact time is very short for effective removal of fats and oils from the erythromycin thiocyanate, a continuous washing method can be devised whereinthe solid erythromycin thiocyanate is forwarded in counter-current flow through trichloroethylene by mechanical or gravitational force.

The simple process of the present invention can be carried out at temperatures between and 50 C. or even higher. Excellent results can be obtained at room temperature and therefore heating or cooling are not required and can be omitted for most economical operation. The volume of trichloroethylene is preferably selected between two and three times the weight of the crude erythromycin thiocyanate; however, larger amounts of trichloroethylene may be used without materially changing the efiiciency of the present process.

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For better understanding of the process of this invention, reference is made to the following examples which are merely added as illustrations and are not intended to limit the invention in any respect.

EXAMPLES 14 Example Before After All numbers given in the above table are measured as international units per mg. of erythromycin thiocyanate (u./mg.). As seen in the table, the potencies of the samples improved materially by the method used to remove the fats and oils.

EXAMPLE 5 A batch of 10 kg. of erythromycin thiocyanate assaying 690 u./mg. was slurried in 25 liters of trichloroethylene for 30 minutes, centrifuged and subsequently washed with 20 liters of trichloroethylene. The material was dried, resulting in 9.5 kg. of purified material assaying 771 u./mg. The obtained material produced a clear 10% solution in methanol.

EXAMPLE 6 In a repetition of Example 5, 10 kg. of erythromycin thiocyanate assaying 705 u./mg. were treated with tri chloroethylene, producing 9.2 kg. of the purified material assaying 761 units per mg.

Samples of this same batch of erythromycin thiocyanate were treated in the above manner prior to drying of the crude precipitate obtained when an erythromycin solution in isoamyl acetate was precipitated by adding an aqueous solution of ammonium thiocyanate and acetic acid. One hundred grams of the material obtained after filtration but prior to drying was slurried in 250 ml. of trichloroethylene, filtered, washed on the filter with 50 ml. of trichloroethylene and dried. The material thus ob tained produced a clear 10% solution in methanol while the material prior to slurrying with trichloroethylene gave a very cloudy solution.

EXAMPLE 7 Erythromycin thiocyanate was prepared by the addition of an aqueous solution of ammonium thiocyanate and acetic acid to an amyl acetate extract of the erythromycin fermentation broth. The precipitate was allowed to settle and the clear solution was decanted. To 400 ml. of the resulting slurry was added ml. of trichloroethylene and the mixture was stirred for 15 minutes before being filtered, washed with 50 ml. of trichloroethylene and, in turn, with 50 m1. of water. The product was dried in vacuo at 45 C.; it produced a clear 10% solution in methanol Whereas a control sample which had no trichloroethylene added and was washed only with an amyl acetate gave a cloudy solution. The potency of the treated product was 801 u./mg., while the untreated sample had a potency of 740 u./ mg.

The process of the present invention is specific to trichloroethylene; many other solvents were found to either remove none or only insufiicient amounts of fats and oils to produce a clear 10% methanol solution, or they resulted in large losses of product due to the solubility of the erythromycin thiocyanate therein. Trichloroethylene readily dissolves substantially all oils and fats found in erythromycin thiocyanate prepared in the usual manner; it is inexpensive, relatively non-toxic, non-inflammable and can be easily recovered by distillation. Trichloroethylene has the further advantage of being easily removable from the final product by drying or by washing it out therefrom.

As seen above, the simple procedure of the present invention can be carried out on the dry, crude erythromycin thiocyanate as well as from the crude material just precipitated, i.e., without necessitating the complete removal of the solvent from the precipitation step in the erythromycin thiocyanate preparation method. The solvents most commonly used in that step are butyl acetate. methyl isobutyl ketone or isoamyl acetate. Remnants of any of these solvents with the crude product do not interfere with the procedure of the present invention.

I claim:

1. The process of purifying erythromycin thiocyanate consisting essentially of contacting one part by weight of erythromycin thiocyanate with at least two parts by volume of trichloroethylene for a period sufliciently long to provide intimate contact between the liquid phase and the solid phase and separating the liquid phase from the solid phase.

2. The process of claim 1 wherein trichloroethylene is used in an amount between 2 and 3 parts by volume per part by weight of erythromycin thiocyanate.

3. The process of claim 1 wherein said erythromycin thiocyanate is slurried in said trichloroethylene for a period of between 5 minutes and 1 hour.

4. The process of claim 1 wherein said liquid phase is separated from said solid phase by filtration.

References Cited UNITED STATES PATENTS 2,653,899 9/1953 Bunch et a1. 2602l0 E 2,791,531 5/1957 Bellard 26021O E 2,806,024 9/1957 Bird, Jr. et a1. 260210 E 2,864,817 12/1958 Croley 2602l0 E 2,870,138 1/1959 Murray 260210 E ELBERT L. ROBERTS, Primary Examiner J. R. BROWN, Assistant Examiner