| JP2011012053 | METHOD FOR PREPARING N-ALKYLAMINO PHENOL |
| JPH01242560 | PRODUCTION OF O-AMINOPHENOLS |
| JPS52122327 | PROCESS FOR PREPARING AMINONITROPHENOLS |
NIDAM TAMAR (IL)
TEVA PHARMA (US)
NIDDAM-HILDESHEIM VALERIE (IL)
NIDAM TAMAR (IL)
| WO2005049560A2 | 2005-06-02 | |||
| WO2007011594A2 | 2007-01-25 | |||
| WO2007067501A1 | 2007-06-14 |
| US4283418A | 1981-08-11 | |||
| US20070135449A1 | 2007-06-14 |
DATABASE BEILSTEIN BEILSTEIN INSTITUTE FOR ORGANIC CHEMISTRY, FRANKFURT-MAIN, DE; XP002466014 retrieved from XFIRE Database accession no. BRN 7872599 & J LABELLED COMPD RADIOPHARM, vol. 40, 1997, pages 762-763,
DATABASE BEILSTEIN BEILSTEIN INSTITUTE FOR ORGANIC CHEMISTRY, FRANKFURT-MAIN, DE; XP002466015 retrieved from XIRE Database accession no. BRN 4194092 & J MED CHEM, vol. 33, no. 10, 1990, pages 3899-2905,
DATABASE CA [Online] CHEMICAL ABSTRACTS SERVICE, COLUMBUS, OHIO, US; STEFANOVSKII, YU. N. ET AL: "Synthesis, configuration, and reduction of dimethylamides of some (+-)-threo-3-hydroxy-2,3-diarylpropanoic acids to aminopropanols" XP002466016 retrieved from STN Database accession no. 69:26952 & COMPTES RENDUS DE L'ACADEMIE BULGARE DES SCIENCES , 21(3), 249-52 CODEN: CRABAA, 1968,
DATABASE CA [Online] CHEMICAL ABSTRACTS SERVICE, COLUMBUS, OHIO, US; FREUDENREICH, CHARLES ET AL: "Design of inhibitors from the three-dimensional structure of alcohol dehydrogenase. Chemical synthesis and enzymic properties" XP002466017 retrieved from STN Database accession no. 100:205537 & JOURNAL OF THE AMERICAN CHEMICAL SOCIETY , 106(11), 3344-53 CODEN: JACSAT; ISSN: 0002-7863, 1984,
What is claimed is: 1. 2-(4-hydroxyphenyl)~N,N-dimethylacetamide having the structure:
2. The 2-(4-hydroxyphenyl)-N,N-dimethylacetamide of claim 1, wherein the compound is characterized by IHNMR (Bruker DPX-300 (DMSO-d6)) with δ: 2.80 (s, CH3-N), 2.96 (s, CH3N), 3.53 (s, CH2), 6.70 (m, H atom), 6.98 (m, H atom), 9.24 (s, OH) and a mass of 180 (MS (CI+)= 180).
3. The 2-(4-hydroxyphenyl)-N,N-dimethylacetamide of claim 1, having a purity of 50% as measured by HPLC.
4. A process for preparing the 2-(4-hydroxyphenyl)-N,N-dimethylacetamide of any preceding claim comprising forming an acid-activated derivative of 4- hydroxyphenylacetic acid (4-hydroxyphenyl)acetic acid), and reacting the activated acid with dimethylamine.
5. A process according to Claim 4 wherein the acid-activated derivative of 4- hydroxyphenylacetic acid is prepared by combining 4-hydroxyphenylacetic acid with an acid activating agent and a catalyst, and optionally recovering the activated acid.
6. A process according to Claim 4 or Claim 5 wherein the activated acid is combined with an amine to obtain OBA, and optionally recovering the OBA.
7. The process of claim 5, wherein the catalyst is an organic catalyst.
8. The process of claim 5, wherein the catalyst is dimethyl formamide (DMF) or Pyridinium p-toluene sulfonate (PPTS).
9. The process of claim 4, 5, or 6, wherein the acid is activated in the presence of a solvent.
10. The process of claim 9, wherein the solvent is selected from a group consisting of Ce- 12 aromatic hydrocarbon, a Ci -4 halogenated hydrocarbon, a C 4 -S ether and mixtures thereof.
11. The process of claim 9, wherein the solvent is selected from a group consisting of toluene, CH 2 Cl 2 and THF.
12. The process of claim 9, wherein the solvent is CH 2 Cl 2 .
13. The process of claim 9, wherein the solvent is cooled to a temperature of about - 40°C to about 70 0 C.
14. The process of claim 13, wherein the solvent is cooled to a temperature of about - 10°C to about 10 0 C.
15. The process of claim 5, wherein the activating agent is SOCl 2 , COCl 2 , DCC (N'- dicyclohexyl carbodiimide) or analogs, HOBT or analogs, or FMOC or analogs.
16. The process of claim 15, wherein the activating agent is SOCl 2 .
17. The process of claim 5, wherein the activated acid is recovered by removing the solvent.
18. The process of claim 5, wherein the dimethylamine is a salt, and subsequent to its reaction with the activated acid, a second amine is added.
19. The process of claim 18, wherein the amine salt is dimethylamine HCl.
20. The process of claim 19, wherein the second amine is a C 3 -C 9 tertiary amine.
21. The process of claim 20, wherein the second amine is diisopropylamine.
22. The process of claim 176, wherein recovery is done by quenching; washing, filtering, and drying.
23. The process of claim 6, further comprising converting OBA to O- desmethylvenlafaxine or a salt thereof.
24. Protected hydroxyphenyl dimethyl amide of the following structure:
25. The protected hydroxyphenyl dimethylamide of claim 24, wherein x is a silyl group or DHP (dihydropyran), acetate, benzyl or benzoyl, preferably a tri(Ci-6 alkyl) silyl group wherein the alkyl group may be the same or different, or THP (tetrahydropyranyl).
26. The protected hydroxyphenyl dimethylamide of claim 24, wherein x is a tri(Ci-6 alkyl) silyl group.
27. The protected hydroxyphenyl dimethylamide of claim 26, wherein the compound is t-butyldimethylsilyl ether (TBDMS)-OBA.
28. The protected hydroxyphenyl dimethylamide of claim 24, wherein x is tetrahydropyranyl.
29. The Protected hydroxyphenyl dimethylamide of claim 24, having a purity of 50% as measured by HPLC.
30. The compound of claim 24-29, wherein the compound is characterized by 1 HNMR with δ: 0.20 (s, Me2Si), 0.99 (s, tBuSi), 2.85 (s, CH3-N), 2,99 (s, CH3N), 3.62 (s, CH2), 6.77 (m, H atom), 7.10 (m, H atom).
31. A process for preparing compound of claim 24 comprising combining OBA with a suitable hydroxyl protecting agent and optionally a base.
32. The process of claim 31, wherein the reaction is done in the presence of a solvent.
33. The process of claim 32, wherein the solvent is an organic solvent, wherein the organic solvent is selected from the group consisting of a Cβ to- C ]2 aromatic hydrocarbon, a Ci-C 6 chlorinated hydrocarbon, and a C 4- s ether.
34. The process of claim 33, wherein the organic solvent is toluene, CH 2 Cl 2 or THF.
35. The process of claim 33, wherein the organic solvent is CH 2 Cl 2 .
36. The process of claim 31, wherein the protecting agent is a silyl protecting group or DHP (dihydropyran).
37. The process of claim 31, wherein the protecting agent is TBDMS-Cl.
38. The process of claim 31, wherein the base is imidazole, pyridine, triethylamine, lutidine or dimethylaminopyridine
39. The process of claim 31, further comprising converting OBA to ODV (O- desmethylvenlafaxine) or a salt thereof.
40. 2-( 1 -hydroxycyclohexyl)-2-(4-hydroxyphenyl)-N,N-dimethylacetamide (COBA) having the following structure:
41. The -(l-hydroxycyclohexyl)-2-(4-hydroxyphenyl)-N,N-dimethylacetamide of claim 40, having a purity of 50% as measured by HPLC.
42. A process for preparing the compound of claim 40 comprising reacting OBA with cyclohexanone and a base able to form a carbanion and recovering the obtained COBA.
43. The process of claim 42, wherein a hydroxy protected OBA is used to obtain a hydroxy protected COBA.
44. The process of claim 42, wherein the reaction is done in the presence of a solvent.
45. The process of claim 44, wherein the solvent is an organic solvent, wherein the orgainc solvent is selected from the group consisting of a C 6 to Cj 2 aromatic hydrocarbon, a Ci-C 6 chlorinated hydrocarbon, and a C 4-8 ether.
46. The process of claim 45, wherein the organic solvent is toluene, CH 2 Cl 2 or THF.
47. The process of claim 46, wherein the organic solvent is CH 2 Cl 2 .
48. The process of claim 46, wherein the solvent is THF.
49. The process of claim 42, wherein OBA is combined with a solvent to obtain a mixture, followed by addition of the base that is able to form a carbanion.
50. The process of claim 42, wherein the base is an alkali metal or alkaline earth metal diisopropylamide or BuLi.
51. The process of claim 49, wherein the base is lithium diisopropylamide.
52. The process of claim 49, wherein the base is sodium hydride (NaH), alkali metal or alkaline earth metal (such as sodium or potassium or lithium) salts of bis trimethylsilylamide {MN(SiMe 3 ) 2 }, metal salt of tert-butoxide (MOtBu)
53. The process of claim 42 wherein recovery comprises quenching, separating layers obtained after quenching, washing organic layer obtained after quenching with brine, and further evaporating residual organic solvent under pressure of less than one atmosphere to obtain COBA or hydroxy protected COBA.
54. Hydroxyl protected 2-(l-hydroxycyclohexyl)-2-(4-hydroxypheny I)-N 5 N- dimethylacetamide (PCOBA) having the following structure:
55. The hydroxyl protected 2-(l-hydroxycyclohexyl)-2-(4-hydroxyphenyl)-N,N- dimethylacetamide of claim 54, wherein the compound is TBDMS-protected COBA.
56. A process for preparing the hydroxyl protected 2-(l-hydroxycyclohexyl)-2-(4- hydroxyphenyl)-N,N-dirnethylacetamide of claim 54-55 comprising reacting a hydroxy protected OBA (POBA) with cyclohexanone and a base able to form a carbanion and recovering the obtained PCOBA.
57. The process for preparing ODV (O-desmethylvenlafaxine) comprising converting the COBA of claim 40 or the PCOBA of claim 54 to ODV or a salt thereof.
58. The process of claim 57, wherein the conversion is carried out by reacting COBA or PCOBA with a reducing agent, and recovering to obtain ODV or a salt thereof.
59. The process of claim 58, wherein the conversion is carried out in tetrahydrofuran (THF).
60. The process of claim 58, wherein the reducing agent is a metal hydride complex.
61. The process of claim 58, wherein the reducing agent is Hydrogen in presence of catalyst
62. The process of claim 60, wherein the metal hydride complex is a BH 3 derivatives or aluminum hydride derivatives.
63. The process of claim 601, wherein the reducing agent is LiAlH 4 or NaBH 4 .
64. The process of claim 60, wherein recovery is carried out by extracting ODV from an aqueous layer by adding a water immiscible organic solvent.
65. The process of claim 64, wherein the water immiscible organic solvent is CH 2 Cb, EtOAc, hexanes or toluene
66. The process of claim 65, further comprising drying, filtering and evaporating pressure of less than one atmosphere.
67. A process for preparing ODV (O-desmethylvenlafaxine) or salts thereof comprising the steps of: combining OBCarboxy, a catalyst and an acid activating agent to obtain an activated acid; recovering the activated acid, combining it with dimethylamine or a salt thereof and an amine to obtain OBA; reacting the obtained OBA with cyclohexanone and a base able to form a carbanion; recovering the obtained COBA; reacting the obtained COBA, and a reducing agent; and recovering the obtained ODV or a salt thereof.
68. The process of claim 67 wherein a protected derivative of OBA (POBA) is used as a starting material for preparing PCOBA 5 and wherein, optionally, a protected derivative of COBA (PCOBA) is used for the preparation of ODV or a salt thereof.
69. A process for preparing ODV (O-desmethylvenlafaxine) or salts thereof comprising the steps of:
(i) preparing OBA from 4-hydroxyphenylacetic acid by a process according to any of Claims 4 to 22;
(ii) optionally preparing POBA from OBA by a process according to any of
Claims 27 to 35;
(iii) preparing COBA from OBA by a process according to any of Claims 42 to 53;
(iv) optionally preparing PCOBA from POBA according to claim 56;
(v) converting the COBA or PCOBA to ODV by a process according to any of
Claims 57 to 68.
70. The process of claim 67 wherein a protected derivative of OBA (POBA) is used as a starting material for preparing PCOBA, and wherein, optionally, a protected derivative of COBA (PCOBA) is used for the preparation of ODV.
71. Use of a compound according to any of Claims 1-3, 23-30, 40-41 and 50-51 in a process for the manufacture of O-desmethylvenlafaxine. |
PROCESS FOR THE SYNTHESIS OF O-DESMETHYLVENLAFAXINE
CROSS REFERENCE TO RELATED APPLICATIONS
The present application claims the benefit of the following United States Provisional Patent Application Nos.: 60/833,616, filed July 26, 2006; 60/837,879, filed August 14, 2006; 60/849,216, filed October 3, 2006; 60/843,998, filed September 11, 2006; 60/849,255, filed October 3, 2006; 60/906,639, filed March 12, 2007; and 60/906,879, filed March 13, 2007. The contents of these applications are incorporated herein by reference.
FIELD OF THE INVENTION
The invention encompasses a process for the synthesis of O- desmethylvenlafaxine.
BACKGROUND OF THE INVENTION
Venlafaxine, (±)-l-[2-(Dimethylamino)-l-(4-methoxyphenyl) ethyl] cyclohexanol, of the following formula,
O-desmethylvenlafaxine, 4-[2-(dimethylamino)- 1 -( 1 -hydroxycyclohexyl) ethyl] phenol, of the following formula,
is reported to be a metabolite of venlafaxine, which is known also as an inhibitor of norepiniphrine and serotonin uptake, See Klamerus, K. J. et al., "Introduction of the Composite Parameter to the Pharmacokinetics of Venlafaxine and its Active O- Desmethyl Metabolite," and J Clin. Pharmacol. 32:716-724 (1992).
Processes for the synthesis of O-desmethylvenlafaxine by demethylation of the methoxy group of venlafaxine are described in U.S. patent Nos. 7,026,508 and in 6,689,912.
The synthesis disclosed in the above patents is performed according to the following scheme:
Reduction
Demethylation phenol
Venlafaxine VNL ODV wherein "MBC" refers to methyl benzyl cyanide, "CMBC" refers to cyclohexyl methylbenzyl cyanide, "DDMV" refers to didesmethyl venlafaxine, and "ODV" refers to O-desmethylvenlafaxine.
The demethylation process disclosed in US patent No.7,026,508 provides ODV succinate salt by using L-selectride, which is an alkali metal salt of trialkyl borohydride; where hydrogen gas is formed during the reaction. Hence, the process isn't suitable for industrial scale manufacture.
US application No.2005/0197392 describes a method for preparing (±) O- desmethylvenlafaxine hydrochloride salt by reacting venlafaxine with lithium diphenyl phosphide.
US patent No.6,689,912 describes demethylation process performed by using a salt of high molecular weight alkane, arene, or arylalkyl thiolate anion in the presence
of protic or aprotic solvent. The salt can be prepared separately and then react with veπlafaxine, or can react in-siru with venlafaxine. When prepared separately, the solvent , methanol should be removed. This operation is very complicated because the mixture containing the salt is highly viscous, hence the operation necessitate long time even under high vacuum. When the reaction is performed in-situ via removal of methanol in situ, this operation is still tedious and only partially successful, since it is difficult to reach the high temperature that the reaction necessitate to advance.
The described ODV synthesis processes are all indirect, i.e; performed via Venlafaxine. The present invention provides a direct synthesis of O- desmethylvenlafaxine; i.e.; without passing through venlafaxine as an intermediate.
SUMMARY OF THE INVENTION In one embodiment, the invention encompasses hydroxyphenyl dimethylamide
(OBA), having the following formula,
In another embodiment, the present invention provides a process for preparing hydroxyphenyl dimethylamide (OBA) comprising combining hydroxybenzyl carboxy (OBCarboxy), a catalyst and an acid activating agent to obtain an activated acid; recovering the activated acid, and combining it with a dimethylamine to obtain OBA.
Preferably, the process for preparing OBA is done in the presence of an organic solvent.
In yet another embodiment, the present invention provides a process for preparing ODV by preparing OBA as described above, and converting it to ODV. OBA can be transformed to ODV via another intermediated such as COBA.
In yet another embodiment, the present invention encompasses hydroxy protected OBA (POBA), having the following formula,
In another embodiment, the present invention encompasses a process for preparing POBA comprising; combining OBA with a hydroxyl protecting agent and a base.
In yet another embodiment, the present invention provides a process for preparing ODV by preparing POBA as described above, and converting it to ODV. POB A'can be transformed to ODV via another intermediated such as PCOBA.
In yet another embodiment, the present invention encompasses cyclohexylOBA (COBA), having the following formula,
In one embodiment the process for the preparation of cyclohexylOBA (COBA) comprising: reacting OBA with cyclohexanone and a base able to form a carbanion; and recovering the obtained COBA.
In yet another embodiment, the present invention provides a process for preparing ODV by preparing COBA as described above, and converting it to ODV 5 by any method known in the art, i.e: the method described above.
In yet another embodiment, the present invention encompasses a hydroxyl protected COBA (PCOBA), having the following formula,
PCOBA
In another embodiment the process for preparing PCOBA comprising; combining POBA with cyclohexanone and a base able to form a carbanion; and recovering the obtained PCOBA.
In yet another embodiment, the present invention provides a process for preparing ODV by preparing PCOBA as described above and converting it to ODV, by any method known in the art, i.e: the method described above.
In another embodiment, the present invention encompasses a process for preparing ODV from COBA comprising: reacting COBA and a reducing agent to obtain ODV, where optionally, PCOBA can be used as a starting material.
In another embodiment, the present invention encompasses a process for preparing ODV comprising the steps of: combining OBCarboxy, a catalyst and an acid activating agent to obtain an activated acid; recovering the activated acid and combining it with an amine to obtain OBA; reacting the obtained OBA with cyclohexanone and a base able to form a carbanion; recovering the obtained COBA and reacting the obtained COBA; a reducing agent; and recovering the obtained ODV, wherein, optionally, a protected derivative of OBA (POBA) can be used as a starting material and PCOBA is obtained, which is then reacted with the reducing agent to obtain ODV.
DETAILED DESCRIPTION OF THE INVENTION
As used herein, the term "ambient temperature" refers to a temperature of about 18°C to about 25°C.
As used herein, the term "OBA" refers to hydroxyphenyl dimethylamide (IUPAC name 2-(4-hydroxyphenyl)-N,N-dimethylacetamide) of the following structure:
As used herein, the term "POBA" refers to protected hydroxyphenyl dimethylamide (IUPAC name: protected 2-(4-hydroxyphenyl)-N,N- dimethylacetamide) of the following structure:
As used herein, the term "COBA" refers to cyclohexyl hydroxyphenyl dimethylamide (IUPAC name 2-(l-hydroxycyclohexyl)-2-(4-hydroxyphenyl)-N,N- dimethylacetamide) of the following structure;
As used herein, the term "PCOBA" refers to protected cyclohexyl hydroxyphenyl dimethylamide (IUPAC name: protected : 2-(l-hydroxycyclohexyl)-2- (4-hydroxyphenyl)-N,N-dimethylacetamide) of the following structure;
As used herein, the term "ODV" refers to O-desmethylvenlafaxine.
The present invention provides a direct synthesis of ODV via novel intermediates. This process produces ODV and its intermediates in high yields and purity. In the process of the present invention ODV is synthesized without going through venlafaxine, leading to elimination of a demethylation step.
In the process of the invention, the intermediate OBA is condensed with cyclohexanone to form the intermediate COBA. Further, the carboxylic group of COBA is reduced, and the reduced product is converted to ODV. The process can be performed via the protected intermediates POBA and PCOBA, in order to increase the yield, due to avoidance of side-reactions. The process is described in the following scheme.
OBCarboxy OBA COBA ODV
POBA PCOBA
In one embodiment, the invention encompasses hydroxyphenyl dimethyl amide (OBA) (IUPAC name 2-(4-hydroxyphenyl)-N,N-dimethylacetamide). OBA is characterized by 1 HNMR (Bruker DPX-300 (DMSO-d6)) with δ: 2.80 (s, CH 3 -N), 2.96 (s, CH 3 N), 3.53 (s 5 CH 2 ), 6.70 (m, H atom), 6.98 (m, H atom), 9.24 (s, OH). OBA has a mass of 180 (MS (CI+)= 180).
In one embodiment the present invention provides isolated or purified OBA. Isolated refers to being separated from the reaction mixture in which it forms. Preferably the OBA is at least about 50% pure as measured by HPLC.
OBA is prepared by a process comprising combining hydroxybenzyl carboxy OBCarboxy (IUPAC name: (4-hydroxyphenyl)acetic acid)) catalyst and an acid
activating agent to obtain an activated acid; recovering the activated acid, and combining it with an amine to obtain OBA.
Preferably, the catalyst is an organic catalyst. Most preferably, the catalyst is dimethyl formamide DMF or Pyridinium p-toluene sulfonate (PPTS). Typically, the reaction is done in the presence of a solvent. The solvent is an organic solvent that does not react with the acid activating agent. More preferably, the solvent is selected from a group consisting of C 6-J2 aromatic hydrocarbon, preferably C 6 to Cs, a C M halogenated hydrocarbon, preferably chloroform, dichloromethane, a C 4-8 ether preferably C 4 to C 6 ether, more preferably tetrahydrofuran, diethylether, methyltert- butyl ether and mixtures thereof. Even more preferably, the solvent is selected from a group consisting of toluene, CH2CI2 and THF. Most preferably, the solvent is CH 2 Cl 2 .
Usually, the reaction with the acid activating agent is exothermic; hence the mixture is cooled prior to combining it with the acid activating agent. Preferably, the mixture is cooled to a temperature of about -10 0 C to about 10 0 C, preferably -5°C to about 5°C, more preferably, to a temperature of about 0 0 C.
In order to decrease the exothermic effect of the reaction, the acid activating agent is added dropwise, preferably during 30 minutes to about 3 hours. Preferably, the acid activating agent is an agent that activates carboxylic acids, i.e., converts the "OH" to a suitable leaving group. The activating agent may be SOCl 2 , COCl 2 , DCC (N'-dicyclohexyl carbodiimide) or analogs, HOBT (N-Hydroxybenzotriazole), FMOC (fluorenylmethoxycarbonyl) or analogs (and other analogs used in peptide chemistry) or PC15 or (COCl) 2 - Most preferably, the activating agent is SOCl 2 .
Following to the addition of the activating agent, the obtained mixture is heated, preferably to a temperature of about 0 0 C to about 30 0 C, preferably about 15°C to about 28°. More preferably the heating is to a temperature of about ambient temperature.
The heated mixture is stirred for a sufficient time to obtain the activated acid, preferably for a period of time of about 0.5 to about 3 hours, preferably for about 1 to about 2.5 hours. More preferably, the stirring is for about 2 hours.
The activated acid is optionally recovered by any method known in the art. Preferably, it is recovered by removing the solvent and providing a residue comprising of the activated acid. One of ordinary skill of art can also devise a one pot process which skips recovery of the intermediate in the synthetic scheme.
Preferably the solvent is removed by evaporation under reduced pressure (pressure of below one atmosphere).
Then, the residue is optionally dissolved in another organic solvent; wherein the solvent is described above. Subsequently, the solution is combined with dimethylamine to provide a mixture. This reaction is more facile if a dimethylamine salt is used, and then the salt is removed with another amine. Preferably the amine salt is dimethylamine-HCl and the second amine is a C3-C9 trialkylamine, where each alkyl chain is independently selected from C1-C7 carbons. Example of such amine includes diisopropylethylamine. A gaseous amine can also be used. Preferably, the second amine is added dropwise, more preferably, during about 1 hour.
The mixture is then stirred for a sufficient time to obtain OBA. Preferably, the stirring is done over a period of time of about 1 hour to about 24 hours more preferably about 4 hours to about 16 hours. More preferably, the stirring is performed overnight.
OBA can be recovered. The recovery is preferably done by quenching the new mixture providing a precipitate; washing, filtering, and drying. Preferably, the quenching is done by adding a saturated solution of a base. More preferably, the base is an inorganic base, such as an alkali metal or alkaline earth metal carbonate/bicarbonate. Most preferably, the base is NaHCO 3 .
Preferably, the precipitate is filtered under a reduced pressure. Preferably, the washing is done with methylene chloride, and the drying, under vacuum (pressure of less than about lOOmmHg). Preferably, the drying is at a temperature of about 2O 0 C to about 8O 0 C. More preferably, the drying is done at room temperature.
The process for preparing OBA can further comprise a process for converting OBA to ODV. OBA can be transformed to ODV via another intermediated such as COBA.
In another embodiment, the present invention encompasses hydroxy protected OBA (POBA). Suitable hydroxy protected groups are listed in T.W. Greene, Protective Groups in Organic Synthesis, (2 nd ed.), which is incorporated herein by reference. Most preferably, POBA is a silyl-protected POBA, such as a M(C] -6 alkyl)silyl-protected POBA, wherein the alkyl groups can be the same or different, preferably t-butyldimethylsilyl ether (TBDMS)-protected OBA, or trimethylsilyl (TMS), with TBDMS being preferred, or DHP-protected OBA.
In one embodiment the present invention provides isolated or purified POBA 5 including TBDMS-OBA. Isolated refers to being separated from the reaction mixture in which it forms. Preferably the POBA is at least about 50% pure as measured by HPLC.
TBDMS-OBA is characterized by 1 HNMR (Bruker DPX-300 (DMSO-d6)) with δ: 0.20 (s, Me2Si), 0.99 (s, tBuSi), 2.85 (s, CH 3 -N), 2,99 (s, CH 3 N), 3.62 (s, CH 2 ), 6.77 (m, H atom), 7.10 (m, H atom).
POBA, including TBDMS-OBA, can be prepared by combining OBA with a suitable hydroxyl protecting agent and a base. An acid may also be used instead of a base.
Usually, the reaction is done in the presence of a solvent. Preferably, the solvent is an organic solvent. Preferably the solvent is a non-protic solvent. The organic solvent can be a C 6 to C 12 aromatic hydrocarbon or a Ci -C O chlorinated hydrocarbon or C 4 . 6 ether. More preferably, the solvent is selected from the group consisting of toluene, CH 2 Cl 2 and THF. Most preferably, the solvent is CH 2 Cl 2 -
Preferably, the hydroxyl protecting agent is a trialkylsilyl halide, preferably a tri(Ci.6 alkyl)silyl halide, wherein the alkyl may be the same or different, preferably the trialkylsilyl halide is a trimethylsilyl halide or a tert-butyldimethylsilyl halide, wherein the halide is chloride or bromide or DHP (dihydropyran). Preferably, the hydroxyl protecting agent is a silyl protecting group or DHP (dihydropyran). More preferably, the hydroxyl protecting agent is TBDMS-Cl, acetylchloride or acetic anhydride.
Preferably, the base is imidazole. Other bases such as pyridine, triethylamine, lutidine, dimethylarninopyridine may also be used.
The obtained combination is stirred at a temperature of about 0 0 C to about 100 0 C, preferably about 40 0 C to about 70 0 C. Preferably, the stirring is done at a temperature of about 55°C.
Preferably the above combination is maintained, while stirring, for about 0.5 hour to about 24 hours, preferably about 1 hour to about 4 hours, more preferably for about two hours, during which POBA is formed.
The process for preparing POBA can further comprise a recovery process.. The recovery is, preferably done by quenching the combination providing a two-phase system; separating the obtained two phases, washing and drying the organic phase, followed by filtering and solvent evaporation under reduced pressure (pressure of less
than one atmosphere). Preferably, the combination is quenched with brine and 10% aqueous solution of citric acid.
The process for preparing POBA can further comprise a process for converting POBA to ODV. POBA can be converted to ODV via COBA or PCOBA.
In another embodiment, the present invention encompasses cyclohexylOBA (COBA). Also provided is isolated or purified COBA. Isolated refers to being separated from the reaction mixture in which it forms. Preferably the COBA is at least about 50% pure as measured by HPLC.
COBA can be prepared by reacting OBA with cyclohexanone and a base able to form a carbanion; and recovering the obtained COBA. Optionally, a protected derivative of OBA can be used as a starting material, to obtain PCOBA.
Usually, the reaction is done in the presence of a solvent. Preferably, the solvent is as described above. More preferably, the solvent is THF.
Initially, OBA or POBA is combined with the solvent to obtain a mixture. Then a base able to form a carbanion is added, providing a new mixture.
Preferably, the base is able to form a carbanion. More preferably, the base is LDA; or alkali metal or alkaline earth metal (such as lithium) diisopropylamide; or BuLi. The base may also be Sodium hydride (NaH); or alkali metal or alkaline earth metal (such as sodium or potassium or lithium) salts of bis trimethylsilylamide {MN(SiMe 3 ) 2 >; or metal salt of tert-butoxide (MOtBu)
The reaction of the base with the reagent is exothermic. Preferably, the base is added at a temperature of about 80 0 C to about 25°C. For example, when the base is LDA, the addition can be done at ambient temperature, and when the base is BuLi, the addition can be done at a temperature of about -80 0 C.
Usually, the base is added dropwise. Preferably, the dropwise addition is done during a period of time of about 30 minutes. The new mixture is then stirred. Preferably, the stirring is for about 10 minutes to about 2 hours. More preferably, the new mixture is stirred for about 30 minutes.
Cyclohexanone is then added to the mixture. Preferably cyclohexanone is added dropwise, more preferably, during a period of time of 30 minutes.
Preferably, the obtained mixture is maintained, while being stirred, for about 30 minutes to about 24 hours, more preferably, the stirring is done overnight.
The reaction mixture can then be quenched, by reacting the reaction mixture with a proton donor, such as NH 4 Cl. The recovery provides COBA or PCOBA, depending on the starting material.
PCOBA and COBA can then be recovered. Preferably, the recovery stage includes: separating the layers obtained after quenching, washing the organic layer obtained after quenching with brine, and further evaporating the residual organic solvent under reduced pressure (pressure of less than one atmosphere) to obtain COBA or PCOBA.
In another embodiment, the present invention encompasses a hydroxyl protected cyclohexylOBA (PCOBA). Preferably, PCOBA is TBDMS -protected COBA.
The process for preparing COBA or PCOBA can further comprise a process for converting COBA or PCOBA to ODV. COBA and PCOBA can be converted to ODV by reacting COBA or PCOBA with a reducing agent, and recovering to obtain ODV.
Usually, COBA or PCOBA are combined with a solvent to obtain a solution. Solvents that are inert to the reducing agent can be used. Preferably the solvent is THF. Subsequently, a reducing agent is added, preferably, the reducing agent is a metal hydride complex. More preferably, the metal hydride complex is selected from a group consisting of BH3 derivatives or aluminum hydride derivatives. Most preferably, the reducing agent is LiAlH 4 , NaBBU, NaBH3CN: sodium cyanoborohydride Instead of using metal hydride complex, the hydrogenation may be performed under H 2 pressure in presence of catalyst such Ni or Co.
Usually, the reducing agent is added dropwise to avoid heat accumulation. The addition can be done during a period of time of about 30 min. The addition can preferably be done at a temperature of about -50 0 C to about RT.. Preferably, the temperature is ambient temperature.
The addition of the reducing agent provides a mixture. Preferably, the mixture is stirred for about 1 hour to about 24 hours. More preferably, the stirring is stirred for over night.
Preferably, the recovery of ODV is done by quenching. More preferably the quenching is done by acidification of the mixture. Acidification is done for example by adding aqueous solution of HCl OrNH 4 Cl. The quenching, typically, provides a two-phase system, comprising of an aqueous phase and of an organic phase. The phases are separated, and the aqueous phase is neutralized preferably, by adding a
base. The neutralization is done by adding a base such as an alkali or alkaline earth metal carbonate/bicarbonate. Preferably, the base is a saturated solution of NaHCOs.
The process for preparing ODV can further comprise a recovery process. The recovery can be done by extracting ODV from the aqueous layer, such as by adding a water immiscible organic solvent. Preferably, the water immiscible organic solvent is CH 2 Cl 2 , EtOAc, hexanes or toluene
The extract may then be dried, filtered and evaporated under reduced pressure (pressure of less than one atmosphere). The drying is preferably over Na 2 SO- J .
One of ordinary skill of art would appreciate that each above described process can be combined into one continuous process for synthesis of ODV. In such process ODV can be synthesized by combining OBCarboxy, a catalyst and an acid activating agent to obtain an activated acid; recovering the activated acid, combining it with an amine to obtain OBA; reacting the obtained OBA with cyclohexanone and a base able to form a carbanion; recovering the obtained COBA; reacting the obtained COBA, and a reducing agent; and recovering the obtained ODV. Optionally, a protected derivative of OBA (POBA) can be used as a starting material for the process for preparing PCOBA, and wherein, optionally, a protected derivative of COBA • (PCOBA) can be used as a starting material for the preparation of ODV.
Having described the invention with reference to certain preferred embodiments, other embodiments will become apparent to one skilled in the art from consideration of the specification. The invention is further defined by reference to the following examples describing in detail the synthesis of the compound OBA, COBA, their protected forms and further their conversion to O-desmethylvenlafaxine. It will be apparent to those skilled in the art that many modifications, both to materials and methods, may be practiced without departing from the scope of the invention.
EXAMPLES
Preparation of OBA Example 1:
A 500ml three-neck flask equipped with nitrogen inlet, thermometer and mechanical stirrer was charged with OBcarboxy (10 g, 65.72mmol), DMF (1ml ) and CH 2 Cl 2 (50 ml). The reaction mixture was stirred at O 0 C and SOCb was added drop wise.
The reaction was stirred at ambient temperature for 2 hours and then the solvent was evaporated under reduced pressure. The residue was dissolved in CH2CI 2 (50 ml) and dimethylamine-HCl (100 g, 1.22 mol) was added. Then diisopropylethylamine (150 ml, 0.882 mol) was added dropwise. The mixture was stirred at ambient temperature overnight and then washed with a saturated solution of NaHCO 3 ; a precipitate appeared. The precipitate was filtered under reduced pressure and washed with methylene chloride. The solid so-obtained was dried in a vacuum oven at room temperature to get 5.55 g of OBA (purity 99.45%).
The organic layer was washed with brine and evaporated to dryness yielding crystals 5.84g OBA (purity 96.57%).Total yield=97.85%.
Preparation of protected OBA (POBA) Example 2:
A 100 ml three-neck flask equipped with nitrogen inlet, thermometer and mechanical stirrer was charged with OBA (2.4 g, 13.39 mmol) TBDMS-Cl (4.5g, 29.9 mmol), imidazole (5.5 g, 80.78 mmol) and CH 2 Cl 2 (20ml). The reaction mixture was stirred at ambient temperature for 2 hours. The reaction was quenched with brine and a 10% aqueous solution of citric acid .The organic phase was then washed with brine and dried over Na 2 SO 4 . After filtration the solvent was evaporated under reduced pressure to get 3.82 g OBA-P (purity: 99.34%, yield: 97.45%). .
Example 3
In a 50 ml flask equipped with a mechanical stirrer, OBA (1.45g, 8.09 mmol) was dissolved at room temperature in DHP (8 ml) under nitrogen. Pyridinium p- toluene sulfonate (PPTS, catalytic amount) was added and the reaction mixture was heated to 55°C for 5 hours. The reaction was monitored by HPLC. EtOAc was added and the organic layer was washed with brine, dried over MgSO 4 and filtered under reduced pressure to get OBA-DHP.
Preparation of protected COBA (PCOBA) Example 4:
A 100 ml three-neck flask equipped with nitrogen inlet, thermometer and mechanical stirrer was charged with OBA-TBDMS (3.8g 12.95mmol) and THF (50ml). The solution was cooled to -8O 0 C and n-BuLi (IM in Hexane 8.5ml
13.6mmol) was added dropwise. The reaction was stirred at -80 ° C for 45 min and cyclohexanone (1.7g, 17.32mmol) was added dropwise. This mixture was stirred for 3 hours at this temperature and poured into a saturated solution of NH 4 Cl. The layers were separated.
The organic layer was washed with brine and dried over Na 2 Sθ4. After filtration the solvent was evaporated under reduced pressure to get 4.85g of COBA-P (purity: 79.63%, yield: 95.65%)
Preparation of COBA via OBA Example 5:
A 100 ml three-neck flask equipped with nitrogen inlet, thermometer and mechanical stirrer was charged with OBA (1.2 g, 6.69mmol) and THF (10 ml).The mixture was stirred at ambient temperature and LDA (2M in THF 7ml, 14.02 mmol) was added dropwise . The mixture was stirred at this temperature for 30 min and cyclohexanone (1.4 g, 14.26 mmol) was added dropwise. This mixture was stirred overnight at ambient temperature and then poured into a NH 4 CI aqueous saturated solution. The layers were separated and the organic phase was washed with brine dried over Na 2 SO 4 and evaporated under reduced pressure to get COBA.
Preparation of ODV via PCOBA Example 6:
A 100 ml three-neck flask equipped with nitrogen inlet, thermometer and mechanical stirrer was charged with PCOB A-TBDMS (2.2 g, 5.6mmoϊ) and THF (30ml). This solution was stirred at ambient temperature and LiAlH 4 (IM in THFlOmI, 10 mmol) was added dropwise. The mixture was stirred at ambient temperature overnight. This mixture was then acidified with a 10% aqueous solution of HCl. The layers were separated and the aqueous phase was basifϊed with a NaHCO 3 saturated solution. The aqueous layer was extracted with CH 2 Cl 2 , dried over Na 2 SO 4 , filtered and evaporated under reduced pressure to get 0.43g of ODV (purity=100%).
Preparation of ODV via COBA Example 7:
A 100 ml three-neck flask equipped with nitrogen inlet, thermometer and mechanical stirrer is charged with COBA-TBDMS (2.2 g, 5.6mmol) and THF (30ml). This solution is stirred at ambient temperature and LiAlH 4 (IM in THFlOmI, 10 mmol) is added dropwise. The mixture is stirred at ambient temperature overnight. This mixture is then acidified with a 10% aqueous solution of HCl. The layers are separated and the aqueous phase is basified with a NaHCOβ saturated solution. The aqueous layer is extracted with CH 2 Cl 2 , dried over Na 2 SO 4 , filtered and evaporated under reduced pressure to obtain ODV.