WO1996028426A1 - N-alkylpipecolic acid compounds, their preparation and use in the synthesis of levobupivacaine and analogues - Google Patents
N-alkylpipecolic acid compounds, their preparation and use in the synthesis of levobupivacaine and analogues Download PDFInfo
- Publication number
- WO1996028426A1 WO1996028426A1 PCT/GB1996/000505 GB9600505W WO9628426A1 WO 1996028426 A1 WO1996028426 A1 WO 1996028426A1 GB 9600505 W GB9600505 W GB 9600505W WO 9628426 A1 WO9628426 A1 WO 9628426A1
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- WO
- WIPO (PCT)
- Prior art keywords
- compound according
- compound
- optically
- enriched
- levobupivacaine
- Prior art date
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D211/00—Heterocyclic compounds containing hydrogenated pyridine rings, not condensed with other rings
- C07D211/04—Heterocyclic compounds containing hydrogenated pyridine rings, not condensed with other rings with only hydrogen or carbon atoms directly attached to the ring nitrogen atom
- C07D211/06—Heterocyclic compounds containing hydrogenated pyridine rings, not condensed with other rings with only hydrogen or carbon atoms directly attached to the ring nitrogen atom having no double bonds between ring members or between ring members and non-ring members
- C07D211/36—Heterocyclic compounds containing hydrogenated pyridine rings, not condensed with other rings with only hydrogen or carbon atoms directly attached to the ring nitrogen atom having no double bonds between ring members or between ring members and non-ring members with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
- C07D211/60—Carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals
Definitions
- This invention relates to the synthesis of (S)- or (-R) -N-alkyl pipecolic acids and esters thereof which can be used in the preparation of optically-active piperidine-2-carboxanilides of formula 1, especially levobupivacaine.
- PL-A-0118594 describes alkylation of racemic pipecolic acid, in boiling toluene.
- Novel compounds according to the present invention are optically-enriched N-alkyl pipecolic acid esters of formula 2, wherein R is C 3-10 alkyl, e.g. C 3-6 alkyl. They are synthesised by alkylation of pipecolic acid.
- the novel compounds preferably exist with an optical purity of at least 50%, more preferably at least 70%, and most preferably at least 90% ee.
- a preferred embodiment of the present invention is a compound of formula 2 of (S) -configuration wherein R is n-butyl; this is a useful precursor to levobupivacaine.
- Synthesis of the key intermediates of formula 2 is of particular importance because access to such compounds makes the synthesis of optically-active piperidine-2-carboxanilides of formula 1 particularly effective, in that the synthesis is made more convergent. In comparing a convergent synthesis to a linear synthesis, a greater percentage of starting material is converted to product in the former case.
- (S)-pipecolic acid is conveniently reacted with an alkyl halide such as n-butyl bromide and base in a suitable polar, e.g. dipolar, aprotic solvent, thereby effecting alkylation at two sites, to generate an (S)-N-alkylpipecolate ester in one step.
- a suitable polar e.g. dipolar, aprotic solvent
- this novel process permits the synthesis of these derivatives to occur under mild conditions and with high yields.
- Suitable solvents for this procedure include hexamethylphosphoramide and, preferably, acetonitrile, dimethylformamide, dimethylacetamide, dimethyl sulphoxide or 1-methyl-2-pyrrolidinone.
- Suitable bases for this reaction include sodium hydroxide and carbonates such as sodium carbonate or, most preferably, potassium carbonate.
- the salts are removed by filtration and the N-alkylpipecolate ester is isolated by direct distillation.
- the reaction mixture may be diluted with water and the product isolated by extraction.
- Conversion of the optically-enriched N-alkylpipecolate ester to optically-enriched N-alkylpipecolic acid may be achieved by saponification with a suitable base such as sodium hydroxide.
- a suitable base such as sodium hydroxide.
- the optically-enriched N-alkylpipecolic acid may be prepared by enantioselective biocatalytic resolution of a racemic compound of formula 2.
Abstract
Optically-enriched N,O-dialkyl pipecolates are useful in the preparation of levobupivacaine and related analgesics. They may be prepared simply by dialkylating optically-enriched pipecolic acid by reaction with an alkylating agent, in the presence of base and a polar aprotic solvent.
Description
N-ALKYLPIPECOLIC ACID COMPOUNDS. THEIR PREPARATION AND USE IN THE SYNTHESIS OF LEVOBUPIVACAINE AND ANALOGUES
Field of the Invention
This invention relates to the synthesis of (S)- or (-R) -N-alkyl pipecolic acids and esters thereof which can be used in the preparation of optically-active piperidine-2-carboxanilides of formula 1, especially levobupivacaine. Background of the Invention
Compounds of formula 1 (see formulae, below) wherein R is methyl, n-propyl, n-butyl or cyclopropyl and R2 is 2 , 6-dimethylphenyl are widely used as local anaesthetics. Biological studies have shown that (S)-enantiomers of such compounds display lower cardiotoxicity than the corresponding racemates whilst maintaining the same anaesthetic potency, and are therefore potentially more beneficial for clinical uses. Thus there is a requirement for efficient processes to manufacture compounds of formula 1 in the form of single enantiomers.
PL-A-0118594, PL-A-0118595, PL-A-0148960, Xue et al, Zhongguo Yiyao Gongye Zazhi 21:250 (1990), and WO-A-8500599 disclose the synthesis of bupivacaine (1: R1 = n-butyl, R2 = 2,6-dimethylphenyl) and ropivacaine (1: R1 = n-propyl, R2 = 2,6-dimethylphenyl, absolute configuration = S) via the intermediate pipecolic acid, and also racemic N-alkyl pipecolic acids. PL-A-0118594 describes alkylation of racemic pipecolic acid, in boiling toluene.
Patrick et al, Chirality 3 (3) : 208-211 (1991), disclose alkylation of (S)-pipecolic acid, en route to thioridazine. The conditions involve heating to reflux, and are suitable for methylation at the N-atom only.
Cervinka et al, Chem. Abs. 111(19):166785v (1989), disclose two-step butylation of enantiomeric 6-methylpipecolic acid. The dibutyl product is then converted to a methyl-substituted analogue of bupivacaine.
Summary of the Invention
Novel compounds according to the present invention are optically-enriched N-alkyl pipecolic acid esters of formula
2, wherein R is C3-10 alkyl, e.g. C3-6 alkyl. They are synthesised by alkylation of pipecolic acid. The novel compounds preferably exist with an optical purity of at least 50%, more preferably at least 70%, and most preferably at least 90% ee. A preferred embodiment of the present invention is a compound of formula 2 of (S) -configuration wherein R is n-butyl; this is a useful precursor to levobupivacaine.
We have discovered that conditions used to alkylate (S)-pipecolic acid do not adversely affect the optical activity of the product. This observation is surprising, in that racemisation of structurally-related piperidine-2-carboxanilides has been observed under both acid and basic conditions (see International Patent Applications Nos. PCT/GB95/02247 and PCT/GB96/00067).
Synthesis of the key intermediates of formula 2 is of particular importance because access to such compounds makes the synthesis of optically-active piperidine-2-carboxanilides of formula 1 particularly effective, in that the synthesis is made more convergent. In comparing a convergent synthesis to a linear synthesis, a greater percentage of starting material is converted to product in the former case.
Description of the Invention
According to this invention, (S)-pipecolic acid is conveniently reacted with an alkyl halide such as n-butyl bromide and base in a suitable polar, e.g. dipolar, aprotic solvent, thereby effecting alkylation at two sites, to generate an (S)-N-alkylpipecolate ester in one step. Surprisingly, this novel process permits the synthesis of these derivatives to occur under mild conditions and with high yields. Suitable solvents for this procedure include hexamethylphosphoramide and, preferably, acetonitrile, dimethylformamide, dimethylacetamide, dimethyl sulphoxide or 1-methyl-2-pyrrolidinone. Suitable bases for this reaction include sodium hydroxide and carbonates such as sodium carbonate or, most preferably, potassium carbonate.
Upon completion of the reaction, the salts are removed by filtration and the N-alkylpipecolate ester is isolated by direct distillation. Alternatively, the reaction mixture may be diluted with water and the product isolated by extraction.
Conversion of the optically-enriched N-alkylpipecolate ester to optically-enriched N-alkylpipecolic acid may be achieved by saponification with a suitable base such as sodium hydroxide. Alternatively, the optically-enriched N-alkylpipecolic acid may be prepared by enantioselective biocatalytic resolution of a racemic compound of formula 2.
The butyl ester of (S)-N-butylpipecolic acid may be used for the preparation of levobupivacaine (1: R = n-butyl, R2 = 2,6-dimethylphenyl, absolute configuration = S), using a process similar to that described in
International Patent Application No. PCT/GB95/02514.
The following Example illustrates the invention.
Example
A round-bottom flask was charged with (S) -pipecolic acid (26 g, 0.2 mol), potassium carbonate (41 g, 0.3 mol), and dimethylformamide (60 ml). Butyl bromide (55 g, 0.4 mol) was then added and the mixture was stirred at 45°C for 18 hours. The suspension was filtered off and the filtrate was evaporated under vacuum to give (S)-butyl N-butylpipecolate (41 g) as a colourless oil.
Claims
1. An optically-enriched compound of formula 2
C3-10 alkyl.
2. A compound according to claim 1, wherein R is C3-6 alkyl.
3. A compound according to claim 1, wherein R is n-propyl.
4. A compound according to claim 1, wherein R is n-butyl.
5. A compound according to any preceding claim, wherein the absolute configuration is (S).
6. A process for preparing a compound according to any of claims 1 to 5, which comprises dialkylating optically-enriched pipecolic acid by reaction with an alkylating agent, in the presence of base and a polar aprotic solvent.
7. A process for preparing a compound according to any of claims 1 to 5, which comprises dialkylating pipecolic acid by reaction with an alkylating agent, in the presence of base and a polar aprotic solvent, followed by resolution.
8. A process according to claim 7, wherein the resolution is effected by enantioselective biocatalysis.
9. A process according to any of claims 6 to 8, wherein the alkylating agent is an alkyl halide.
10. A process according to claim 6, wherein (S)-pipecolic acid is reacted with n-butyl bromide.
11. A process according to any of claims 6 to 10, wherein the solvent is acetonitrile, dimethylformamide, dimethylacetamide, dimethyl sulphoxide or 1-methyl-2- pyrrolidinone.
12. A process according to any of claims 6 to 11, wherein the base is potassium carbonate.
13. Use of a compound according to any of claims 1 to 5, or the product of a process according to any of claims 6 to 12, for the preparation of a corresponding optically-enriched analgesic agent in which the ester group is converted to 2,6-dimethylphenylamino.
14. Use according to claim 13, wherein the compound is according to claim 5 and the agent is levobupivacaine.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU48862/96A AU4886296A (en) | 1995-03-10 | 1996-03-05 | N-alkylpipecolic acid compounds, their preparation and use in the synthesis of levobupivacaine and analogues |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9504876.5 | 1995-03-10 | ||
GBGB9504876.5A GB9504876D0 (en) | 1995-03-10 | 1995-03-10 | Compounds and process |
Publications (1)
Publication Number | Publication Date |
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WO1996028426A1 true WO1996028426A1 (en) | 1996-09-19 |
Family
ID=10770995
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB1996/000505 WO1996028426A1 (en) | 1995-03-10 | 1996-03-05 | N-alkylpipecolic acid compounds, their preparation and use in the synthesis of levobupivacaine and analogues |
Country Status (4)
Country | Link |
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AU (1) | AU4886296A (en) |
GB (1) | GB9504876D0 (en) |
WO (1) | WO1996028426A1 (en) |
ZA (1) | ZA961911B (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR100844336B1 (en) | 2007-01-16 | 2008-07-07 | 하나제약 주식회사 | New synthetic method of levobupivacaine and its hydrochloride |
US11890422B2 (en) | 2022-05-05 | 2024-02-06 | Pfof Llc | Anesthetic nerve block and method |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2955111A (en) * | 1957-01-28 | 1960-10-04 | Bofors Ab | Synthesis of n-alkyl-piperidine and n-alkyl-pyrrolidine-alpha-carboxylic acid amides |
WO1985000599A1 (en) * | 1983-08-01 | 1985-02-14 | A/S Apothekernes Laboratorium For Specialpraeparat | L-N-n-PROPYLPIPECOLIC ACID-2,6-XYLIDIDE AND METHOD FOR PREPARING THE SAME |
US4695576A (en) * | 1984-07-09 | 1987-09-22 | Astra Lake Medel Aktiebolag | L-N-n-propylpipecolic acid-2,6-xylidide |
-
1995
- 1995-03-10 GB GBGB9504876.5A patent/GB9504876D0/en active Pending
-
1996
- 1996-03-05 AU AU48862/96A patent/AU4886296A/en not_active Abandoned
- 1996-03-05 WO PCT/GB1996/000505 patent/WO1996028426A1/en active Application Filing
- 1996-03-08 ZA ZA961911A patent/ZA961911B/en unknown
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2955111A (en) * | 1957-01-28 | 1960-10-04 | Bofors Ab | Synthesis of n-alkyl-piperidine and n-alkyl-pyrrolidine-alpha-carboxylic acid amides |
WO1985000599A1 (en) * | 1983-08-01 | 1985-02-14 | A/S Apothekernes Laboratorium For Specialpraeparat | L-N-n-PROPYLPIPECOLIC ACID-2,6-XYLIDIDE AND METHOD FOR PREPARING THE SAME |
US4695576A (en) * | 1984-07-09 | 1987-09-22 | Astra Lake Medel Aktiebolag | L-N-n-propylpipecolic acid-2,6-xylidide |
Non-Patent Citations (3)
Title |
---|
CHEMICAL ABSTRACTS, vol. 100, no. 25, 1984, Columbus, Ohio, US; abstract no. 209638s, W. KULICKI ET AL.: "Lower alkylesters of N-alkylpipecolic acids" page 579; XP002003469 * |
CHEMICAL ABSTRACTS, vol. 111, no. 19, 1989, Columbus, Ohio, US; abstract no. 166785v, R.G. GLUSHKOV ET AL.: "Substituted anilides of 6-methylpipecolic acid" page 15; XP002003470 * |
KHIM.-FARM. ZH., vol. 23, no. 7, 1989, pages 820 - 824 * |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR100844336B1 (en) | 2007-01-16 | 2008-07-07 | 하나제약 주식회사 | New synthetic method of levobupivacaine and its hydrochloride |
US11890422B2 (en) | 2022-05-05 | 2024-02-06 | Pfof Llc | Anesthetic nerve block and method |
Also Published As
Publication number | Publication date |
---|---|
AU4886296A (en) | 1996-10-02 |
GB9504876D0 (en) | 1995-04-26 |
ZA961911B (en) | 1997-03-10 |
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