One pot synthesis of 2-oxazolidinone derivatives

The present invention relates to an improved process for the preparation of substituted indole derivatives, which are useful for the treatment and prophylaxis of migraine. More specifically, the present invention provides an improved process for the preparation of the 5-HT receptor receptor agonist, (S) -4 - {[37 [2- (dimethylamino) ethyl] -1H-indol-5-yl] methyl} -2 -oxazolidinone, which is known to be effective for the treatment of migraine.

Selective 5-HT receptor agonists are known to be active therapeutic agents. The 5-HT-like receptor mediates vasoconstriction and thus alters blood flow to the carotid vascular bed. European Patent Publication 0313397 describes a class of 5-HT receptor agonists that are beneficial for the treatment or prophylaxis of conditions in which vasoconstriction is indicated in the vascular bed of the carotid, for example migraine, a condition associated with excessive dilation of the vascular system of the carotid.

International publication WO91 / 18897 describes another class of compounds presenting a receptor agonism "similar to 5-HT! exceptional and excellent absorption after oral dosing. These properties make the compounds disclosed in WO91 / 18897, respectively, particularly useful for certain medical applications, namely migraine prophylaxis and treatment, cluster headache and headache associated with vascular disorders, which we will refer to below. , with the generic name “migraine”. A particularly preferred compound, described in WO91 / 18897, is (S) -N, N-dimethyl-2- [5- (2-ox <? - 1,3-oxazolidin-4-yl-methyl) -1H -indol-3-yl] ethylamine, which is also known as (S) -4 - {[3- [2- (dimethylamino) ethyl] -1H-indol-5yl] methyl} -2-oxazolidinone and can be represented by formula I:

<img file="RO119618B1_D0001.tif" />

The compound of formula I may exist in the form of its (S) or (R) enantiomer and is specifically exemplified in WO91 / 18897. In WO91 / 18897, a number of possible pathways for the preparation of the compound of formula I are suggested.

A new process has now been discovered for the preparation of the compound of formula I. This process is advantageous over the processes described in WO91 / 18897 in that it allows the final product to be obtained in a large scale and pure form through the use of a process in a single reactor, thus avoiding the need to isolate time-consuming and expensive intermediates. The new process also avoids the need for hazardous reagents such as phosgene or environmentally hazardous reagents such as tin chloride.

The present invention relates to an improved process for the preparation of (S) -4 - {[3 [2- (dimethylamino) ethyl] -1H-indol-5-yl] methyl} -2-oxazolidinone, of formula I:

<img file="RO119618B1_D0002.tif" />

which includes the stages of:

RO 119618 Β1

a) formation of a carbamate from methyl 4-nitro- (L) -phenylalaninate hydrochloride,

<img file="RO119618B1_D0003.tif" />

by adding sodium carbonate, sodium bicarbonate or n-butyl chloroformate and their reaction to give methyl- (S) -N-butoxycarbonyl-4-nitrophenylalanine, represented by formula III:

<img file="RO119618B1_D0004.tif" />

c₄h₉a₂CHN

<img file="RO119618B1_D0005.tif" />

co₂ch₃

b) reduction of the compound of formula III, to give methyl (S) -N-butoxycarbonyl-4-amino-phenylalaninate, represented by formula IV:

<img file="RO119618B1_D0006.tif" />

c) reduction of methyl -CO ester group₂CH₃ of the compound of formula IV to give (S) -N-butoxycarbonyl-4-aminophenylalaninol represented by formula V: 31

<img file="RO119618B1_D0007.tif" />

d) closing the ring of the compound of formula V to give (S) -4- (4-aminobenzyl) -2oxazolidinone, represented by formula VI:

<img file="RO119618B1_D0008.tif" />

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e) preparation of the diazonium salt of compound VI, followed by reduction to give hydrazine (S) -4- (4-hydrazinobenzyl) -2-oxazolidinone hydrochloride, represented by the formula

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<img file="RO119618B1_D0009.tif" />

NHNHjHCl (VII)

f) Fischer reaction of the compound of formula VII, to give the compound of formula I, wherein steps a) to d) are carried out by a process in a single reactor, followed by the isolation of the compound of formula VI and then a second one process in a single reactor for steps e) and f).

The invention also relates to the intermediates represented by formulas III, IV and V,

C ^ EjOjCHN

<img file="RO119618B1_D0010.tif" />

(ΙΠ)

<img file="RO119618B1_D0011.tif" />

<img file="RO119618B1_D0012.tif" />

used to carry out the process of preparation of (S) -4 - {[3- [2- (dimethylamino) ethyl] -1H-indol5-yl] methyl} -2-oxazolidinone of formula I.

The invention also relates to a process for the preparation of a compound of formula III:

<img file="RO119618B1_D0013.tif" />

which comprises the reaction of a compound of formula II:

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<img file="RO119618B1_D0014.tif" />

(Π) with sodium carbonate, or sodium bicarbonate and n-butyl chloroformate.

Another aspect of the invention relates to a process for the preparation of a compound of formula IV:

<img file="RO119618B1_D0015.tif" />

<img file="RO119618B1_D0016.tif" />

which comprises reducing a compound of formula III.

<img file="RO119618B1_D0017.tif" />

(ΙΠ) In another aspect, the invention relates to a process for the preparation of a compound of formula V:

<img file="RO119618B1_D0018.tif" />

which includes the reduction of a compound of formula IV:

<img file="RO119618B1_D0019.tif" />

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Also, the present invention relates to a process for the preparation of a compound of formula VI:

<img file="RO119618B1_D0020.tif" />

which comprises closing a ring in the compound of formula V.

<img file="RO119618B1_D0021.tif" />

The present invention further relates to the use of intermediates with formulas III,

IV and V for the preparation of a compound of formula I, which is contained in a composition, for use in medicine.

Another aspect of the invention relates to the use of intermediates of formulas III, IV and

V for the preparation of a compound of formula I, which is contained in a composition used in the treatment of migraine.

The advantages of the process of the present invention over the processes described in WO 91/18897 consist in the fact that this process allows the final product to be obtained in a large-scale and pure form, by using a process in a single reactor, avoiding thus the need to isolate time-consuming intermediaries is costly. The new process also avoids the use of hazardous reagents, such as phosgene, or environmentally hazardous reagents such as tin chloride.

Suitably, one or more of steps a) to f) are performed using a one-step process. Preferably steps a) to d) are performed by a one-step procedure, followed by isolation of the compound of formula VI and then another one-step procedure for steps e) and f). Step a) is suitably carried out in the presence of a solvent, for example aqueous ethyl acetate or dioxane. Aqueous ethyl acetate is preferred. Sodium carbonate is preferred to sodium bicarbonate and is preferably added before n-butyl chloroformate. The reaction is suitably carried out at moderate temperature, suitably between 5 and 60 ° C. Preferably the reaction is carried out at 15 ... 35 ° C. In one particularly preferred embodiment, the addition of sodium carbonate occurs at a temperature of about 20 ° C and the addition of Nbutyl chloroformate takes place at a temperature of about 30 ° C. The reduction step b) is suitably carried out in the presence of an organic solvent, for example ethyl acetate or ethanol. Preferably, step b) is carried out by a process in a single reactor, using the ethyl acetate solution of the compound of formula III, which results from step a). Suitably, step b) is carried out by hydrogenation, preferably in the presence of a catalyst such as palladium on coal. The reaction can be carried out under a nitrogen atmosphere, using hydrogen at atmospheric pressure, at room temperature. The idiom is preferably performed

EN 119618 Β1 at about 20 psi hydrogen, at a high temperature, for example 30 to 50C. 1

The solution of the compound of formula IV in ethyl acetate, as a result, is preferably transformed into a butanolic solution that can be used directly, as part of a process in a single reactor, in step c). This transformation can be suitably carried out by partially distilling the ethyl acetate solution, followed by the addition of butanol and fractionation to remove the ethyl acetate. The reduction of the methyl ester from step c) is suitably carried out in the presence of a solvent, for example SVM or n-butanol. Preferably, step c) 7 is carried out as part of a process in a single reactor, by preparing a solution in n-butanol from a solution in ethyl acetate of the compound of formula IV and then directly reducing the solution to n- butanol. The reduction is preferably carried out using sodium borohydride and is conveniently carried out at a moderate temperature, suitably 11

20 .. .40'C. Preferably, the reduction is carried out in two phases: the first phase being carried out under nitrogen at a temperature of about 25 ° C, the second phase being carried out at 13 about 30 ° C. The resulting n-butanol solution of the compound of formula V can then be dried using hydrochloric acid and ammonia. The dried n-butanolic solution can be used directly in step d) as part of a process in a single reactor. Step d) is preferably carried out on a dry solution, for example a dry butanolic solution of compound 17 of formula V. Such a dry butanolic solution can advantageously be prepared by drying the n-butanolic solution resulting from step c. ). The dried n-butanolic solution is preferably bleached using charcoal, prior to the ring closure reaction, the ring closure may advantageously be carried out using sodium methoxide, suitably 21 in an alcoholic solvent, for example methanol. Most preferably, the ring closure is performed using a solution of sodium methoxide in 30% methanol. The reaction is preferably carried out at a high temperature which is suitably within the range

50 .. .20 ° C. Preferably, the reaction is carried out at about 85'C. The resulting compound of formula VI can then be isolated. This isolation can be performed by standard centrifugation, filtration and drying methods. 27

Step e) is preferably performed on the isolated compound of formula VI. Isolation can be performed, for example, using well-known centrifugation, filtration and drying techniques. The formation of the diazonium salt can be carried out using an aqueous solution of sodium nitrite, preferably in the presence of concentrated hydrochloric acid, at low temperature. Preferably, salt formation is carried out at low temperature, for example O ... 5 ° C.

Hydrazine formation is then carried out from the diazonium salt solution using sodium sulfite 33 as reducing agent. Sodium sulfite is suitably in the form of an aqueous solution. The reduction is advantageously carried out in two phases: the first consisting of the addition of sodium sulphite; the second consisting of the addition of hydrochloric acid. Preferably, the first phase is carried out at a temperature below 10 ° C. The second phase is preferably 37 carried out at a high temperature, for example 55 ... 60 ° C.

The solution of the compound of formula VII, which results from step e) is preferably 39 directly used in step f) as a process in a single reactor. Step f) is a Fischer reaction.

It was found to be advantageous to perform this reaction at a relatively high dilution to maximize the purity of the final product. Accordingly, the solution resulting from step e) is preferably diluted with water. The Fischer reaction is then carried out by adding 4,4-43 diethoxy-N, N-dimethylbutylamine, suitably under a nitrogen atmosphere. Preferably, when 4,4-diethoxy-N, N-dimethylbutylamine is added, the diluted solution is at a high temperature. 45 A suitable temperature is in the range 75 ... 105 ° C and is preferably about 90 ° C. The reaction preferably occurs at reflux. 47

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When the reaction is complete, the compound of formula I can be extracted using standard techniques. Suitably, the reflux reaction product is cooled and brought to a pH of about 7, for example by using sodium hydroxide. The pH-adjusted product can then be extracted with ethyl acetat e and the pH-adjusted aqueous layer about 10 with sodium hydroxide. The product can be extracted at about 50 * C, followed by standard bleaching, filtration, distillation, centrifugation and drying techniques. A reaction scheme, particularly preferred for the preparation of the compound of formula I, is:

<img file="RO119618B1_D0022.tif" />

<img file="RO119618B1_D0023.tif" />

Status -UMoxiaxborul-4-n ^ {«mHaitinci

<img file="RO119618B1_D0024.tif" />

<img file="RO119618B1_D0025.tif" />

<img file="RO119618B1_D0026.tif" />

Bowhidrnn of sodh n-tatand (5&gt; -N-Betu? 0c ^ ibcrd-4-ainHwfcr »fal3rant&gt; l mefaxid of srxfai a-fcutaaol

<img file="RO119618B1_D0027.tif" />

<img file="RO119618B1_D0028.tif" />

Methyl-S) -N-bixocuau ^ oafl-4- * KanoGsiilabjiinate (P Nitru dececttu. Acid darhidrie (2) Sulfitda todin, Hydrochloric acid

<img file="RO119618B1_D0029.tif" />

dodadxot of (^ 4- (4-HdraztaobartziI ^ 2-aia3 &lt;Jici * o «a (S) -4- (Â-munobMui&gt; 2- &lt;i3tflaaManc« ei

<img file="RO119618B1_D0030.tif" />

Purification of (S) -4 - {[3- [2- (dimethylamino) ethyl] -1H-indol-5-yl] methyl} -2-oxazolidinone can be carried out by a process comprising the steps of:

a) dissolution of (S) -4 - {[3- [2- (dimethylamino) ethylJ-1H-indol-5-yl] methylj-2-oxazolidin one in a mixture at reflux of ethanol in ethyl acetate; filtering the hot solution;

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b) slow cooling of the filtered solution to a temperature of about 5'C; 1

c) centrifuging the product from step b), washing with ethyl acetate and then drying; and

d) treatment with acetone to remove solvated ethyl acetate. 3

Preferably, the reflux mixture is 10% ethanol in ethyl acetate. The hot solution is suitably bleached using bleach coal prior to filtering, using an auxiliary filter material. The filtered, cooled solution of step b) is suitably stirred before centrifugation for a prolonged period, which is preferably about 18 hours. The drying step of step c) is preferably carried out in vacuo. Suitably, the product is dried at a moderate temperature, for example 4O ... 6O "C, which is preferably about 9 to 50'C. The dry solid product of step c) is advantageously treated with a mixture of 20% acetone in water, at moderate temperatures, preferably 15-30 ° C, 11 for example at room temperature. The resulting slurry is then cooled to a reduced temperature, preferably about 5'C and stirred. The product is then centrifuged, washed with 13 ethyl acetate and dried, preferably in vacuo, at a temperature of about 45 ° C.

The resulting product is an unsolvated solid, of high purity.15

In a third aspect, the present invention provides pure, unsolvated (S) -4 - {[3- [2- (dimethylaminojethyl] 1H-indol-5-yl] methyl} -2-oxazolidinone. 17

In other respects, the invention provides compounds of the formulas III, IV, V and VI defined above.19

In other aspects, the invention provides processes for the preparation of compounds of formulas III, IV, V and VI as follows.21

Compound (III): process step a) from the first aspect of the invention and, preferably, as described on page 6;

Compound (IV): process step b) from the first aspect of the invention and, preferably, as described in the paragraph on page 6;

Compound (V): process step c) from the first aspect of the invention and, preferably, as described on page 7; şi27

Compound (VI): procedure d) from the first aspect of the invention and, preferably, as described on page 8.29

The invention will now be described by the following examples:

Example 1. Process for large-scale preparation of (S) -4 - {[3- [2- (dimethylamino) 31 ethyl] -1H-indol-5-yl] methyl} -2-oxazolidinone

PHASE 1: Preparation of methyl 4-nitro- (L) -phenylalaninate hydrochloride33

<img file="RO119618B1_D0031.tif" />

C1₀H13N₂A₄CI ^ 9 ^ 10 ^ 2 ^ 4

M. molec. 210.18

M. molec. 260.67

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<td>MATERIALS</td><td>AMOUNT</td><td>MOLI</td>

<td>4-nitro- (L) -phenylalanine</td><td>100.0 kg</td><td> 475,8 .</td>

<td>methanol</td><td> 599,01</td><td></td>

<td>HCl</td><td>45.3 kg</td><td> 1241,6</td>

<td>Methanol (washing)</td><td> 66,81</td><td></td>

Prepare a methanolic hydrochloric acid solution by passing gaseous hydrochloric acid to a reactor containing methanol, maintaining the temperature below 25 ° C. Charge in the reactor 4-nitro- (L) -phenylalanine and reflux for about 1 hour. Cool to about 0 ° C and centrifuge the product (methyl 4-nitro- (L) -phenylalanine hydrochloride). The product was washed with methanol and dried under vacuum at 50 ° C.

PHASE 2: Preparation (S) -N-butoxycarbonyl-4-nitrophenylalaninate of methyl

<img file="RO119618B1_D0032.tif" />

<td>MATERIALS</td><td>QUANTITY [kg]</td><td>MOLI</td>

<td>Methyl 4-nitro- (L) -phenylalanine hydrochloride</td><td> 45,0</td><td> 172,7</td>

<td>sodium carbonate</td><td> 20,1</td><td> 189,6</td>

<td>N-butyl chloroformate</td><td> 24,0</td><td> 175,8</td>

<td>Ethyl acetate</td><td> 248,0</td><td></td>

<td>Water (demineralized)</td><td> 100,0</td><td></td>

<td>Water (washing)</td><td> 50,0</td><td></td>

Procedure

The demineralized water, methyl 4-nitro (L) -phenylalanine hydrochloride, sodium carbonate and ethyl acetate are charged to the reactor and the contents are cooled to about 20 ° C with stirring. The n-butyl chloroformate is added to the reaction mixture, the temperature is maintained at about 30 ° C and stirred for about 30 minutes. Separate the aqueous layer and wash the ethyl acetate solution with water. The solution in ethyl acetate of methyl (S) -Nbutoxycarbonyl-4-nitrophenylalaninate is used directly in the next step.

PHASE 3: Preparation (S) -N-butoxycarbonyl-4-aminophenylalaninate of methyl

<img file="RO119618B1_D0033.tif" />

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QlS ^ O ^ Og C₁₅H22N₂A₄

Μ. Molec. 324.33 Μ. Molec. 294.33

<td>MATERIALS</td><td>AMOUNT</td><td>MOLI</td>

<td>(S) Methyl N-butoxycarbonyl-4-nitrophenylalaninate</td><td>56.0 kg</td><td> 172,7</td>

<td>Ethyl acetate</td><td>252.0 kg</td><td></td>

<td>5% palladium on coal (humidity 55% water)</td><td>5.0 kg</td><td></td>

<td>Ethyl acetate (filter wash)</td><td>18.0 kg</td><td></td>

<td>sodium carbonate</td><td>12.5 kg</td><td></td>

<td>Water (demineralized)</td><td>100.0 kg</td><td></td>

<td>Auxiliary filtering material</td><td>3.5 kg</td><td></td>

<td>Hydrogen</td><td>as needed</td><td></td>

<td>butanol</td><td>247.1 kg</td><td></td>

Procedure

The catalyst 5% palladium catalyst is charged to the reactor, the ethyl acetate solution of methyl (S) -N-butoxycarbonyl-4-nitrophenylalaninate and hydrogenated at about 20 psi hydrogen, maintaining the temperature between 30 and 50 ° C. At the end of the reaction, the catalyst is filtered through the auxiliary filter material and washed with ethyl acetate. Wash the ethyl acetate solution with an aqueous sodium carbonate solution. The solution in ethyl acetate of methyl (S) -N-butoxycarbonyl-4-aminophenylalaninate is partially distilled, butanol is added and the mixture is fractionated to remove ethyl acetate. Butanolic solution is used directly in the next phase.

PHASE 4: Preparation (S) -N-butoxycarbonyl-4-aminophenylalaninol

<img file="RO119618B1_D0034.tif" />

C₁₅H₂₂N₂A₄ c₁₄h₂₂n₂a₃

M. molec. 294.33 M. molec. 266.34

<td>MATERIALS</td><td>AMOUNT</td><td>MOLI</td>

<td>Methyl (N) -N-Butoxycarbonyl-4-aminophenylalaninate</td><td>50.8 kg</td><td> 172,8</td>

<td>n-butanol</td><td>305 I</td><td></td>

<td>Sodium borohydride (total)</td><td>6.5 kg</td><td> 172,8</td>

<td>Hydrochloric acid conc.</td><td>20.2 I</td><td> 300,0</td>

<td>Water (demineralized - for acid dilution)</td><td>20.2 kg</td><td></td>

<td>Water (demineralized)</td><td>150.0 kg</td><td></td>

<td>Ammonia solution conc. (d = 0.88)</td><td>14.6 I</td><td></td>

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Procedure

The butanolic solution of (S) -N-butoxycarbonyl-4-aminophenylalaninate from phase 3 is charged to the reactor and diluted to the required volume with n-butanol. Cool the reactor contents to about 25 ° C. Under a nitrogen atmosphere add half the amount of sodium borohydride required, while maintaining the reaction temperature at about 25 ° C. Stir for 3 hours and then add the second half of sodium borohydride. The mixture is further stirred for 5 hours and heated to 35'C. After this time the reaction mixture is stirred for 12 hours and then slowly aqueous hydrochloric acid is added, maintaining the temperature at about 30 ° C, to decompose any excess sodium borohydride. Water is added, heated to about 35 ° C and ammonia solution is added to adjust the pH to about pH 10. The aqueous layer was separated and, maintaining the temperature at about 35 ° C, the organic layer was washed with water. Part of the butanol is distilled, while the solution is dried by azeotropic distillation. The dried butanol solution is used directly in the next step.

PHASE 5: Preparation of (S) -4- (4-aminobenzyl) -2-oxazolidinone

<img file="RO119618B1_D0035.tif" />

C₁₄H₂₂N₂A₃ c₁₀h₁₂n₂a₂

M. molec. 266.34 M. molec. 192.21

<td>MATERIALS</td><td>AMOUNT</td><td>MOLI</td>

<td>(S) -N-butoxycarbonyl-4-aminophenylalaninol</td><td>91.9 kg</td><td> 345,0</td>

<td>n-butanol</td><td>260.0 liters</td><td></td>

<td>Sodium methoxide (30% solution in methanol)</td><td>7.5 kg</td><td> 4,7</td>

<td>Coal</td><td>2.0 kg</td><td></td>

<td>n-butanol (wash on filter)</td><td>20.0 kg</td><td></td>

<td>n-butanol (product wash)</td><td>30.0 kg</td><td></td>

<td>Auxiliary filtering material</td><td>2.0 kg</td><td></td>

Procedure

The dried solution of (S) -N-butoxycarbonyl-4-aminophenylalaninol in n-butanol from phase 4 is charged to the reactor and bleaching carbon is added. The dried solution is treated at about 85 ° C by the gradual addition of sodium methoxide in methanol. Heat the reaction mixture at 85 ° C for an additional 30 minutes and then filter hot through the auxiliary filter material. After cooling the solution to 5-10 ° C for at least 8 hours, the mixture is centrifuged, the filtered product is washed with n-butanol and dried at about 50 ° C in vacuo.

f

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PHASE 6A: Preparation of (S) -4 - {[3- [2- (dimethylamino) ethyl] -1H-indol-5-yl] methyl} -2-oxazolidinone

<img file="RO119618B1_D0036.tif" />

hydrochloric acid ic

C₁₀H₁₂N₂A₂

M. molec 192.21

<img file="RO119618B1_D0037.tif" />

N (CH₃)₂

C₁₆H₂₁N₃A₂

M. molec. 287.36

<td>MATERIALS</td><td>AMOUNT</td><td>MOLI</td>

<td>(S) -4- (4-aminobenzyl) -2-oxazolidinone</td><td>19.2 kg</td><td> 100,0</td>

<td>Sodium nitrite</td><td>6.9 kg</td><td> 100,0</td>

<td>Sodium sulfite</td><td>37.8 kg</td><td> 300,0</td>

<td>Concentrated hydrochloric acid</td><td>66.6 kg</td><td></td>

<td>4,4-diethoxy-N, N-dimethylbutylamine</td><td>19.0 kg</td><td> 100,0</td>

<td>Sodium hydroxide solution 32% w / w.</td><td>60.0 kg</td><td></td>

<td>Ethyl acetate (total extract)</td><td>303.0 I</td><td></td>

<td>Coal</td><td>2.9 kg</td><td></td>

<td>Water (demineralized)</td><td>412.8 kg</td><td></td>

<td>Ethyl acetate (washing)</td><td>10.0 I</td><td></td>

<td>Auxiliary filtering material (total used)</td><td>2.0 kg</td><td></td>

Procedure

The concentrated hydrochloric acid, demineralized water and (S) -4- (4- 35 aminobenzyl) -2-oxazolidinone are charged into the reactor. Cool the contents of the reactor to between 0 and 5 ° C, and add an aqueous solution of sodium nitrite, maintaining the temperature below 5 ° C. After stirring for 37 minutes for about 30 minutes, add the solution of diazonium salt to an aqueous solution of cooled sodium sulfite, maintaining the temperature below 10 ° C. After stirring for 15 minutes, the resulting mixture was slightly warmed to about 55 ... 60 "C and then slowly added hydrochloric acid. The solution is maintained at about 60 "C for about 18 hours. The reaction mixture is diluted with water and heated to about 90 ° C. Under a nitrogen atmosphere

RO 119618 Β1 gradually adds 4,4-diethoxy-N, N-dimethylbutylamine and is heated to reflux for about 3h. Cool and bring the mixture to pH 7, using sodium hydroxide solution. Extract with ethyl acetate and then bring the aqueous layer to pH about 10, again using sodium hydroxide solution. The product was extracted at about 50 ° C using ethyl acetate. The combined extracts of ethyl acetate (containing the product) are treated with bleaching charcoal and filtered through the auxiliary filter material. Distill most of the solvent and cool the suspension to about 5 * C. The crude product was centrifuged, the ethyl acetate was washed and dried in vacuo at 50 ° C.

PHASE 6B: Purification of (S) -4 - {[3- [2- (dimethylamino) ethyl] -1H-indol-5-yl] methyl} -2-oxazolidinone

<td>MATERIALS</td><td>AMOUNT</td>

<td>Ethyl acetate</td><td>109.4 I</td>

<td>ethanol</td><td> 12,31</td>

<td>Coal</td><td>2.4 kg</td>

<td>Ethyl acetate (product wash)</td><td> 5,01</td>

<td>Acetone</td><td> 11,81</td>

<td>Water (demineralized)</td><td>47.3 kg</td>

<td>Water (demineralized) (product wash)</td><td>10.0 kg</td>

<td>Auxiliary filtering material</td><td>2.0 kg</td>

The crude product from step 6A is dissolved in a mixture of 10% ethanol reflux in ethyl acetate, treated with bleaching charcoal and hot filtered through the auxiliary filter material. The solution is cooled slowly to above 5 ° C and stirred for 18h. The purified product is then centrifuged, washed with ethyl acetate and then dried in vacuo at 50 ° C. Results (S) -4 - {[3- [2- (dimethylamino) ethyl] -1H-indol-5-yl] methyl} -2-oxazolidinone solvated with ethyl acetate containing about 17% by weight ethyl acetate. The solvated product is characterized by its X-ray diffraction model shown in fig. 2. To remove the solvated ethyl acetate, the dry solid is added to a mixture of 20% acetone in water at ambient temperature and stirred for 1 h. The suspension is cooled to about 5 ° C for about 1 hour before centrifugation of the product, washed with ethyl acetate and dried in vacuo at about 45 ° C. Unsolved (S) -4 - {[3- [2- (dimethylamino) ethyl] -1H-indol-5-yl] methyl) -2-oxazolidinone, containing less than 0.3% ethyl acetate, is characterized by its X-ray diffraction model shown in fig. 1.

Example 2. Alternative preparation of methyl (S) -N-butoxycarbonyl-4-nitrophenylalaninate (Compound of formula (III))

A mixture of methyl-4-nitro- (L) -phenylalanine hydrochloride (40.00 g, 0.153 mol) and sodium bicarbonate (73 g, 0.870 mol) in 1,4-dioxane (1000 ml) is stirred at about 10 ° C under anhydrous conditions. A solution of butyl chloroformate (23.12 g, 21.52 ml, 0.169 mol) in 1.4 dioxane (200 ml) was added for 10 min (reaction temperature about 13 ° C). The resulting suspension is allowed to warm to room temperature and stirred for three hours. The reaction mixture was slowly poured into water (1600 ml) and then extracted with ethyl acetate (3 x 650 ml). The combined extracts of ethyl acetate were washed with brine (1000 ml),

EN 119618 Β1 dry over anhydrous magnesium sulphate, filter and evaporate until an oil is obtained. 1 The residual solvent is removed using an oil pump at 50 * 0, resulting in a syrup (51.34 g, 103% yield) which solidifies through residence. 3

TLC [SiO₂, EtOAc] is homogeneous (R₍ = 0,59) ¹H-NMR (60 MHz, CDCl₃) corresponds to the carbamate structure.5

Example 3. Alternative preparation of methyl (S) -N-butoxycarbonyl-4-aminophenylalaninatuluide methyl (Compound of formula (IV)) 7

A solution of the compound prepared in Example 2 [45.00 g, 0.139 moles] in ethanol (845 ml) was added to palladium on 10% wet coal (Type 87L, 61.1% H₂O) [~ 4.5 g] under 9 nitrogen atmosphere. The reaction is performed for hydrogenation at room temperature, at atmospheric pressure. The hydrogen consumption is constant (~ 9700 ml) for more than 9 h. The catalyst is filtered on "Hyflo" and washed with ethanol (100 ml). The filtrate is concentrated in vacuo (water bath temperature &lt;40 ° C) and the last traces of solvent are removed using 13 oil pumps, resulting in a brown gum (41.70 g, 101%).

TLC [SiO₂, EtOAc] indicates the desired product (R₍ = 0.49) with traces of an impurity with R_f 15 higher.

1 H-NMR (300 MHz, CDCl₃) corresponds to the structure of the product and the residual ethanol. 17

Example 4. Alternative preparation of (S) -N-butoxycarbonyl-4-aminophenylalaninol (Compound of formula (V)) 19

To a suspension of sodium borohydride (14.80 g, 0.390 mol) in SVM (150 ml), under stirring, a solution of the compound prepared in example 3 (76.40 g, 21 0.260 mol) is added dropwise. in SVM (460 ml) at room temperature. The reaction is stirred overnight (- 18 h), followed by TLC (SiO₂, EtOAc) indicates the complete consumption of 23 raw materials. The reaction mixture was brought to pH 4 with 2M aqueous hydrochloric acid, ice-cold, at a temperature of about 10 ° C. The resulting mixture is concentrated to a solid residue up to 25 and a saturated aqueous sodium bicarbonate solution (2000 ml) is added slowly. The aqueous mixture (pH ~ 8) was extracted with ethyl acetate (2 x 750 ml) and the combined organic extracts 27 dried (magnesium sulfate), filtered and concentrated to a light pink waxy solid (64.56 g, 93% yield). 29

TLC [SiO₂, EtOAc] indicates the desired product (R_f = 0.33) with traces of impurities.

H-NMR (60 MHz, CDCl₃) is corresponding to the structure of alaninol. 31