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Title:
IMPROVED METHOD OF MAKING AMPHETAMINE FREE BASE
Document Type and Number:
WIPO Patent Application WO/2007/041571
Kind Code:
A1
Abstract:
An improved method of making amphetamine free base.

Inventors:
BUENGER, Greg, S. (1947 Gil Avenue, Charles City, Iowa, 50616, US)
HUMPHREY, Judi, C. (407 Howard Street, Charles City, Iowa, 50616, US)
Application Number:
US2006/038606
Publication Date:
April 12, 2007
Filing Date:
October 03, 2006
Export Citation:
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Assignee:
CAMBREX CHARLES CITY, INC. (1205 11th Street, Charles City, Iowa, 50616, US)
BUENGER, Greg, S. (1947 Gil Avenue, Charles City, Iowa, 50616, US)
HUMPHREY, Judi, C. (407 Howard Street, Charles City, Iowa, 50616, US)
International Classes:
C07B57/00; C07C209/00; C07C211/00
Foreign References:
US20040220277A12004-11-04
US3028430A1962-04-03
Attorney, Agent or Firm:
HEMMENDINGER, Lisa, M. (BANNER & WITCOFF LTD, 1001 G Street, N.W., Eleventh Floo, Washington DC, 20001-4597, US)
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Claims:
CLAIMS

1. A method of preparing amphetamine free base, comprising:

(a) contacting an aqueous solution of amphetamine salt having a pH of not less than 10 with a first organic solvent to form an aqueous phase and an organic phase; and

(b) withdrawing the aqueous phase from the organic phase, wherein the organic phase comprises the amphetamine free base.

2. The method of claim 1 wherein the amphetamine salt is a ^-amphetamine salt.

3. The method of claim 1 wherein the amphetamine salt is a ^-amphetamine salt.

4. The method of claim 1 further comprising a step of exchanging the first organic solvent for a second organic solvent.

5. The method of claim 1 further comprising exposing the first or second organic solvent to a dessicant.

6. The method of claim 1 wherein the organic solvent is selected from the group consisting of an alkyl ester of an organic acid, an ether, a hydrocarbon, an amine; a pyrrolidine, and an alcohol.

7. The method of claim 6 wherein the organic solvent is an alkyl ester of an organic acid and the alkyl ester of the organic acid is selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, n-propyl acetate, and n-butyl acetate.

8. The method of claim 6 wherein the organic solvent is an ether and the ether is methyl tert-butyl ether.

9. The method of claim 6 wherein the organic solvent is a hydrocarbon and the hydrocarbon is selected from the group consisting of an aliphatic hydrocarbon, an aromatic hydrocarbon, and a halogenated hydrocarbon.

10. The method of claim 9 wherein the hydrocarbon is an aromatic hydrocarbon and the aromatic hydrocarbon is toluene.

11. The method of claim 9 wherein the hydrocarbon is an aliphatic hydrocarbon and the aliphatic hydrocarbon is selected from the group consisting of octane, heptane, hexane, and pentane.

12. The method of claim 9 wherein the hydrocarbon is a halogenated hydrocarbon and the halogenated hydrocarbon is dichloromethane.

13. The method of claim 6 wherein the organic solvent is an amine and the amine is selected from the group consisting of a cyclic amine and an alkylamine.

14. The method of claim 13 wherein the amine is a cyclic amine and the cyclic amine is selected from the group consisting of pyridine, l,5-diazabicyclo[5.4.0]undec-7-ene (DBU), l,4-diazabicyclo[2.2.2]octane (DABCO), and pyrrolidine.

15. The method of claim 13 wherein the amine is an alkyl amine and the alkyl amine is selected from the group consisting of a primary alkyl amine, a secondary alkyl amine, and a tertiary alkyl amine.

16. The method of claim 5 wherein the organic solvent is an alcohol and the alcohol is n-butanol.

17. The method of claim 6 wherein the organic solvent is in an amount which provides between 1 to 100 moles of organic solvent per mole equivalent of d- or d,l- amphetamine resident in the amphetamine salt.

18. The method of claim 1 wherein the pH is adjusted to 10.5 to 11.5.

19. The method of claim 5 wherein the dessicant is sodium chloride.

20. The method of claim 1 wherein the pH is adjusted to not less than 12.5.

Description:

IMPROVED METHOD OF MAKING AMPHETAMINE FREE BASE

FIELD OF THE INVENTION

[01] The invention relates to the preparation of d- or d, /-amphetamine free base.

DETAILED DESCRIPTION OF THE INVENTION

[02] The invention provides improved methods of making d- or d, /-amphetamine (1 -methyl, 2-phenyl ethylamine; 2-amino-propylbenzene) free base from an amphetamine salt, such as both d and dl (racemic) forms of amphetamine sulfate (mono- or di-basic), amphetamine hydroiodide, amphetamine adipate, amphetamine carboxymethylcellulose salt, amphetamine hydrochloride, amphetamine phosphate (mono- or di-basic), amphetamine saccharate, amphetamine aspartate, or amphetamine tannate. Amphetamine salts can be prepared, for example, as disclosed in U.S. Patent 1,879,003; U.S. Patent 4,224,246; and U.S. Patent 6,399,828, each of which is incorporated herein by reference in its entirety.

[03] The method generally involves the following steps: aqueous dissolution, pH adjustment, extraction, and de- watering {e.g., drying). A d- or d, /-amphetamine salt is first dissolved in water to form an aqueous solution. The amphetamine salt preferably is J-amphetamine sulfate. -Amphetamine sulfate is available commercially, for example, from Sigma- Aldrich. The pH of the aqueous solution preferably is not less than 10, more preferably 10.5 to 11.5, and can be 12.5 and higher. The pH can be adjusted using a caustic agent such as an alkali metal hydroxide or alkoxide {e.g., NaOH, KOH, LiOH), a basic ion exchange polymer resin; an organic amine {e.g., NKH 2 ; NR 2 H; NR 3 , where R is an alkyl, e.g., C 1 -C 4 ), ammonium hydroxide, sodium carbonate, potassium carbonate, and the like. Sodium hydroxide is generally used due to its availability and cost.

[04] The aqueous solution is then contacted with an extracting medium. In some embodiments the extracting medium is an organic solvent, such as an alkyl ester of an

organic acid (e.g. methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, n-propyl acetate, or n-butyl acetate); an ether such as methyl tert-butyl ether (MTBE); an aliphatic or aromatic hydrocarbon (e.g., toluene, octane, heptane, hexane, pentane), a halogenated hydrocarbon (e.g., dichloromethane); a cyclic amine such as pyridine, 1,5- diazabicyclo[5.4.0]undec-7-ene (DBU), l,4-diazabicyclo[2.2.2]octane (DABCO), or pyrrolidine; a primary, secondary, or tertiary alkyl amine; or an alcohol (e.g., n-butanol). Other suitable organic solvents can easily be chosen by one skilled in the art. Generally, an amount of the organic solvent should be used to provide between 1 to 100 moles (e.g., between 1-10, 5-10, 5-15, 10-20, 15-25, 20-30, 25-50, 30-40, 40-50, 45-70, 50-75, 55-70, 60-80, 65-85, 75-100, 80-90, 90-100 moles) of organic solvent per mole equivalent of d- or d, /-amphetamine resident in the amphetamine salt.

[05] The aqueous phase is withdrawn from the organic phase. Well known techniques and equipment can be used to perform the organic extraction. The aqueous phase is then contacted with additional organic solvent, and a second aqueous phase is withdrawn from the organic phase. Any residual water is removed from the organic solvent phase, preferably by exposing it to a dessicant. The dessicant can be, for example, magnesium perchlorate (e.g., ANHYDRONE®), calcium chloride, calcium sulfate, magnesium sulfate, sodium sulfate, or sodium chloride. Other ways of removing any residual water will be apparent to the skilled worker.

[06] The d- or <i, /-amphetamine free base prepared according to these embodiments can be used without further purification as an intermediate or starting material in reaction schemes which employ the same organic solvent (e.g., isopropyl acetate). Alternatively, the organic solvent used for the exteactioiL.caa.bjg exchangedjfoxajiifferent solvent, such as those listed above.

[07] In another embodiment the d- or d, /-amphetamine free base is phase-separated from the aqueous solution of d- or d, /-amphetamine salt. This can be done, for example, by

neutralizing the solution to approximately pH 10 or greater using a suitable base. The resulting d- or < i, /-amphetamine free base separates as a liquid phase.

[08] The invention provides cost-effective methods of preparing d- or d, /-amphetamine free base of high purity. Amphetamine is a well-known stimulant. A d- or d, /-amphetamine free base prepared according to the invention also is useful in animal models. For example, the d- or d, /-amphetamine free base can be dissolved in a physiologically acceptable solvent, such as saline, and used to challenge experimental animals in in vivo models of motor coordination and agility.

[09] The above disclosure generally describes the present invention. A more complete understanding can be obtained by reference to the following specific embodiment, which is provided for purposes of illustration only and is not intended to limit the scope of the invention.

EXAMPLE 1

[10] Water (960 ml) was added to a reaction vessel containing 12O g ^-amphetamine sulfate (mw 368.49). The pH was adjusted to not less than 12.5 using 50% sodium hydroxide (61 g). Isopropyl acetate (522 g) was added to the d-amphetamine solution. The aqueous phase was removed and extracted with isopropyl acetate. Remaining water was then removed by exposing the isopropyl acetate solution to MgSO 4 .

EXAMPLE 2

[11] Water (960 ml) was added to a reaction vessel containing 12O g d-amphetamine sulfate (mw 368.49). TheψH was adjusted tσ ~ t&5=i 1.5 using 50% sodium hydroxide (61 g). Isopropyl acetate (522 g) was added to the ^-amphetamine solution. The aqueous phase was removed and extracted with isopropyl acetate. Remaining water was then removed by exposing the isopropyl acetate solution to a sodium chloride solution.