Process for the preparation of 2-oxazolidinone derivatives, intermediates for such process and their preparation and the use of the said derivatives in the manufacture of compositions for use in medicine

156733/2 ononi no i>bnn toj> o»io ,p3O>bUNVpiN-2 nnuj nonb *pbnn flwaia w»>vb trvuon too nba imtrn

PROCESS FOR THE PREPARATION OF 2-OXAZOLIDINONE DERIVATIVES, INTERMEDIATES FOR SUCH PROCESS AND THEIR PREPARATION AND THE USE OF THE SAID DERIVATIVES IN THE MANUFACTURE OF COMPOSITIONS FOR USE IN MEDICINE PAT/5357 P/15357/103838/527461/l 1

The present application was divided out of Israel Patent Application IL 123171 (“the parent application”) and relates to compounds useful as intermediates in an improved process for preparing substituted indole derivatives, which are useful for the treatment and prophylaxis of migraine and to the processes for the preparation of such intermediates. More particularly, the present invention provides compounds useful as intermediates in an improved process for the preparation of the 5HTi-like receptor agonist (S)-4-{[3-[2-(dimethylamino)ethyl]-lH-indol-5-yl]methyl}-2-oxazolidinone, which is known to be effective for the treatment of migraine.

Selective 5-HTi-like receptor agonists are known to be useful therapeutic agents. The 5-HTi-like receptor mediates vasoconstriction and thus modifies blood flow in the carotid vascular bed. European patent specification 0313397 describes a class of specific 5-HTi-like receptor agonists which are beneficial in the treatment or prophylaxis of conditions wherein vasoconstriction in the carotid vascular bed is indicated, for example, migraine, a condition associated with excessive dilation of the carotid vasculature.

International patent specification WO 91/18897 describes a further class of compounds having exceptional "5-HTi-like" receptor agonism and excellent absorption following oral dosing. These properties render the compounds disclosed in WO 91/18897 particularly useful for certain medical applications, notably the prophylaxis and treatment of migraine, cluster headache and headache associated with vascular disorders, hereinafter referred to collectively as "migraine". One particularly preferred compound described in WO 91/18897 is (S)-N,N-dimethyl-2-[5-2oxo-l,3-oxazolidin-4-yl-methyl)-lH-indol-3-yl]ethyl amine which is also known as (S)-4-{[3-[2-(dimethylamino)ethyl]-lH-indol-5-yl]methyl}-2-oxazolidinone and can be represented by formula (I):

O

<img img-format="tif" img-content="drawing" file="IL156733AD00021.tif" id="idf0001" />

<img img-format="tif" img-content="drawing" file="IL156733AD00022.tif" id="idf0002" />

Ν(ΟΗ3&gt;2 2

The compound of formula (I) can exist as its (S) or (R) enantiomer and is specifically exemplified in WO 91/18897. A number of possible routes for preparing the compound of formula (I) are suggested in WO 91/18897. A new process for preparing the compound of formula (I) has now been discovered, which is the subject of the parent application. This process is advantageous over the processes disclosed in WO 91/18897 in that it allows the final product to be made at a high yield on a large scale and in pure form by using a one-pot procedure, thus avoiding the need for time-consuming and costly isolation of intermediates. The new process also avoids the need for dangerous reagents such as phosgene or environmentally hazardous reagents such as tin chloride.

According to the first aspect of the invention claimed in the parent application, there is provided a process for the preparation of a (S)-4-{[3-[2(dimethylamino)ethyl]-lH-indol-5-yl]methyl}-2-oxazolidinone which process comprises the steps of: a) forming a carbamate from methyl 4-nitro-(L)-phenylalaninate hydrochloride, represented by formula (II)

<img img-format="tif" img-content="drawing" file="IL156733AD00023.tif" id="idf0003" />

(Π) by adding sodium carbonate or sodium hydrogen carbonate and n-butyl chloroformate and reacting to give methyl(S)-N-butoxycarbonyl4-nitrophenylalaninate, represented by formula (III) b) reducing the compound of formula (III) 3

<img img-format="tif" img-content="drawing" file="IL156733AD00024.tif" id="idf0004" />

b) reducing the compound of formula (HI) to give methyl (S)-N-butoxycarbonyl-4· amino phenylalaninate, represented by formula (IV)

<img img-format="tif" img-content="drawing" file="IL156733AD00025.tif" id="idf0005" />

(IV) c) reducing the methyl ester grouping -CO2CH3 in the compound of formula (IV) to give (S)-N-butoxycarbonyl-4-aminophenylalaninol, represented by formula (V)

<img img-format="tif" img-content="drawing" file="IL156733AD00026.tif" id="idf0006" />

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

<img img-format="tif" img-content="drawing" file="IL156733AD00027.tif" id="idf0007" />

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

<img img-format="tif" img-content="drawing" file="IL156733AD00028.tif" id="idf0008" />

f) Fischer reaction of the compound of formula (VII) to give the compound of formula (I)

Suitably, one or more of steps a) to f) are carried out using a one pot procedure. Preferably steps a) to d) are carried out by a one pot procedure followed by isolation of the compound of formula (VI) and then a second one pot procedure for steps e) and f).

Step a) is conveniently carried out in the presence of a solvent e.g. aqueous ethyl acetate or dioxane. Aqueous ethyl acetate is preferred. Sodium carbonate is used in preference to sodium hydrogen carbonate and is preferably added prior to the n*butyl chloroformate. The reaction is conveniently carried out at a non-extreme temperature, suitably in the range 5-60°C. Preferably the reaction is carried out at 15-35°C. In a particularly preferred embodiment the addition of sodium carbonate takes place at a temperature of approximately 20°C and the addition of N-butyl chloroformate takes place at a temperature of approximately 30°C.

The reduction step b) is conveniently carried out in the presence of an organic solvent, e.g. ethyl acetate or ethanol. Preferably step b) is carried out by a one pot procedure using the ethyl acetate solution of the compound of formula (III) which results from step 5 a). Suitably, step b) is carried out by hydrogenation, preferably in the presence of a catalyst such as palladium charcoal. The reaction may be carried out under an atmosphere of nitrogen using hydrogen at normal atmospheric pressure at room temperature. Hydrogenation is preferably carried out at approximately 20psi of hydrogen at an elevated temperature e.g. 30°C to 50°C. The resulting ethyl acetate solution of the compound of formula (IV) is preferably converted into a butanol solution which can be used directly, as part of a one pot procedure, in step c). This conversion can conveniently be carried out by partial distillation of the ethyl acetate solution followed by addition of butanol and fractionation to remove the ethyl acetate.

The methyl ester reduction of step c) is conveniently carried out in the presence of a solvent e.g. SVM or n-butanol. Preferably step c) is carried out as part of a one pot procedure by preparing a n-butanol solution from the ethyl-acetate solution of the compound of formula (TV) and then directly reducing the n-butanol solution. The reduction is preferably effected using sodium borohydride and is conveniently carried out at a non-extreme temperature suitably 20-40°C. Preferably, the reduction is carried out in two phases; the first phase being carried out under nitrogen at a temperature of approximately 25°C; and the second phase being carried out at approximately 30°C. The resulting n-butanol solution of the compound of formula (V) can then be dried using hydrochloric acid and ammonia. The dry n-butanol solution can be used directly in step d) as part of a one pot procedure.

Step d) is preferably carried out on a dry solution, e.g. a dry butanol solution, of the compound of formula (V). Such a dry butanol solution is advantageously prepared by drying the n-butanol solution which is produced by step c). The dry n-butanol solution is preferably decolourised using charcoal before carrying out the ring closure reaction. The ring closure can be conveniently effected using sodium methoxide, suitably in an alcoholic solvent e.g. methanol. Most preferably, the ring closure is carried out using a 30% solution of sodium methoxide in methanol. The reaction is preferably carried out at an elevated temperature which is suitably in the range 50-120°C. Preferably the reaction is carried out at approximately 85°C. The resulting compound of formula (VI) may then be isolated. This isolation can be carried out by standard centrifugation, filtration and drying methods. 6

Step e) is preferably carried out on the isolated compound of formula (VI). Isolation can be achieved, for example, using well known centrifugation, filtration and drying techniques. Piaronium salt formation can be carried out using aqueous sodium nitrite solution, preferably in the presence of concentrated hydrochloric acid, at a reduced temperature. Preferably the salt formation is carried out at a reduced temperature, e.g. 0-5°C. Hydrazine formation is then carried out on the diazonium salt solution by using sodium sulphite as a reducing agent. The sodium sulphite is suitably in the form of an aqueous solution. The reduction is advantageously carried out in two phases: the first being addition of sodium sulphite; the second being addition of hydrochloric acid. Preferably the first phase is carried out at a temperature below 10°C. The second phase is preferably carried out at an elevated temperature e.g. 55-60°C.

The solution of the compound of formula (VII) which results from step e) is preferably used directly in step f) as a one pot procedure. Step f) is a Fischer reaction. It has been found to be advantageous to carry out this reaction at a relatively high dilution in order to maximise the purity of the final product. Accordingly the solution which results from step e) is preferably diluted with water. The Fischer reaction is then carried out by adding 4,4-diethoxy-H.N-dimethylbutylamine, suitably under a nitrogen atmosphere. Preferably, when the 4,4-diethoxy-N,N-dimethylbutylamine is added, the diluted solution is at an elevated temperature. A suitable temperature is in the range 75-105°C, and is preferably approximately 90°C. The reaction preferably proceeds under reflux.

When the reaction is complete, the compound of formula (I) can be extracted using standard techniques. Suitably the refluxed reaction product is cooled and adjusted to about pH7, e.g. using sodium hydroxide. The pH adjusted product can then be extracted with ethyl acetate and the aqueous layer adjusted to about pH 10 with sodium hydroxide. The product can then be extracted at approximately 50°C, followed by standard decolourising, filtration, distillation, centrifugation and drying techniques. A particularly preferred reaction scheme for the preparation of the compound of formula (I) is

<img img-format="tif" img-content="drawing" file="IL156733AD00029.tif" id="idf0009" />

(1) Sodium carbonate, water ethyl acetate (2) n-Butylchlorofbrmate (ΙΠ)

C^H^OjCHN

<img img-format="tif" img-content="drawing" file="IL156733AD000210.tif" id="idf0010" />

Methyl (S&gt;-N-butoxycarbonyl-4-nltrophenylalaninote

Hydrogen, 5% Palladlum/charcoal ethyl acetate n-butanol

<img img-format="tif" img-content="drawing" file="IL156733AD000211.tif" id="idf0011" />

(S)-N-Butoxy carbonyl-4-amlnophenylalanInol

Methyl (S}-N-butoxycarbonyl-4-amlnophenyialanlnate sodium methoxide n-butnnol

<img img-format="tif" img-content="drawing" file="IL156733AD000212.tif" id="idf0012" />

(1) Sodium nitrite, hydrochloric add (2) Sodium sulphite, hydrochloric add

<img img-format="tif" img-content="drawing" file="IL156733AD000213.tif" id="idf0013" />

(S)-4-(4-Hydr&amp;amp;zlnobenzyl)-2-oxazolidlnone hydrochloride

<img img-format="tif" img-content="drawing" file="IL156733AD000214.tif" id="idf0014" />

(CjHgO^CIKCH^NiCIl^j 4,4-Methoxy-N,N-dlmethylbutylamIne N(CH3)2

The present invention provides compounds of formulae (III), (IV), (V) and (VI) as defined hereinbefore.

In a further aspect, the invention provides processes for preparing compounds of formulae (III), (IV), (V) and (VI), as follows: A process for the preparation of a compound of formula III, being the process of step (a) described in the text bridging pages 2 and 3 and preferably as described on page 4; A process for the preparation of a compound of formula IV, being the process of step (b) described on page 3 and preferably as described in the text bridging pages 4 and 5; A process for the preparation of a compound of formula V, being the process of step (c) described on page 3 and preferably as described on page 5; A process for the preparation of a compound of formula VI, being the process of step (d) described in the text bridging pages 3 and 4 and preferably as described on page 5; 10

The invention will now be further described by the following examples. EXAMPLE 1 A process for preparing (S)-4-[2-(dimethylamino)ethyl]-lH-indol-5-yl]methyl}-2 oxazolidinone in bulk. STAGE 1: The preparation of methyl 4-nitro-(L)-phenylaninate hydrochloride

REACTION

<img img-format="tif" img-content="drawing" file="IL156733AD000215.tif" id="idf0015" />

C9HioN204 Ci0H13N2O4C1 M.W. 210.18 M.W. 260.67 MATERIALS QUANTITY MOLES 4-Nitro-(L)-phenylanine 100.0 kg 475.8 Methanol 599.0 liters Hydrogen chloride 45.3 kg 1241.6 Methanol (wash 66.8 liters

PROCEDURE

Prepare a methanolic solution of hydrogen chloride by passing hydrogen chloride gas into a reactor containing methanol, maintaining temperature below 25°C. Charge to the reactor the 4-nitro-(L)-phenylanine and reflux for about 1 hour. Cool to about 0°C and centrifuge the product (methyl 4-nitro-(L)-phenylalaninate hydrochloride). Wash the product with methanol and dry in vacuo at 50°C. 11 STAGE 2: The preparation of methyl (S)-N-butoxvcarbonvl-4-nitroDhenvlalaninate

REACTION

<img img-format="tif" img-content="drawing" file="IL156733AD000216.tif" id="idf0016" />

C10H13N2O4C1 M.W. 260.67 c15H20N2°6 M.W. 324.33 MATERIALS QUANTITY MOLES Methyl 4-nitro-(L)-phenylalaninate hydrochloride 45.0kg 172.7 Sodium carbonate 20.1kg 189.6 n-Butyl chloroformate 24.0kg 175.8 Ethyl acetate 248.0kg Water (demineralised) 100.0kg Water (wash) 50.0kg

PROCEDURE

Charge to the reactor demineralised water, methyl 4-nitro-(L)-phenylalaninate hydrochloride, sodium carbonate and ethyl acetate and cool the contents to about 20°C with stirring. Add the n-butyl chloroformate to the reaction mixture whilst maintaining the temperature at about 30°C and stir for about 30 minutes. Separate the aqueous layer and wash the ethyl acetate solution with water. The ethyl acetate solution of methyl (S)-N-butoxycarbonyl-4-nitrophenylalamnaie is used directly at the next stage. 12 STAGE 3: The preparation of methvl fS)-N-butoxvcarbonvl-4-aminophenylaniQate

REACTION

<img img-format="tif" img-content="drawing" file="IL156733AD000217.tif" id="idf0017" />

Cl5H20N2°6 C15H22N2O4 M.W. 324.33 M.W. 294.33 MATERIALS QUANTITY MOLES Methyl (£)-N-butoxycarbonyl-4- 56.0kg 172.7 nitrophenylaianinate Ethyl acetate 252.0kg 5% Palladium charcoal (55% water wet) 5.0kg Ethyl acetate (filter wash) 18.0kg Sodium carbonate 12.5kg Water (demineralised) 100.0kg Filter aid 3.5kg Hydrogen as required Butanol 247.1kg

PROCEDURE

Charge to the reactor the 5% palladium charcoal catalyst, the ethyl acetate solution of methyl (S)-N-butoxycarbonyl-4-nitrophenyialaninate and hydrogenate at about 20 psi of 13 hydrogen, maintaining a temperature between 30°C and 50°C. On completion, filter off the catalyst through filter aid and wash with ethyl acetate. Wash the ethyl acetate solution with aqueous sodium carbonate solution. The ethyl acetate solution of methyl (S)-N-butoxycarbonyl-4-aminophenylaianinate is partially distilled, butanol added and the mixture fractionated to remove the ethyl acetate. The butanol solution is used directly at the next stage. STAGE 4: The preparation of fS)-N-butoxvcarbonvl-4-aminoDhenvlalaninol.

REACTION c4h9o2chn

<img img-format="tif" img-content="drawing" file="IL156733AD000218.tif" id="idf0018" />

n-butanol co2ch3

Sodium, borohydride, ethanol c4h9o2chn

<img img-format="tif" img-content="drawing" file="IL156733AD000219.tif" id="idf0019" />

C15H22N2O4 M.W. 294.33 C14H22N2°3 M.W. 266.34 MATERIALS QUANTITY MOLES Methyl (S)-N-butoxycarbonyl-4- 50.8kg 172.8 aminophenylaminate n-Butanol 305 litres Sodium borohydride (total) 6.5kg 172.8 cone. Hydrochloric acid 20.2 litres 300 Water (demineralised - for dilution of acid) 20.2kg Water (demineralised) 150.0kg cone. Ammonia solution (d=0.88) 14.6 litres 14

PROCEDURE

Charge to the reactor the butanol solution of methyl (S)-M-butoxycarbonyl-4-aminophenylalaninate from Stage 3, and dilute with n-butanol to the required volume. Cool the reactor contents to about 25°C. Under a nitrogen atmosphere add half the amount of sodium borohydride whilst maintaining a reaction temperature of about 25°C. Stir for 3 hours and then add the second half of sodium borohydride. Further stir the mixture for 5 hours and warm to 35°C. After this time stir the reaction mixture for about 12 hours and then slowly add aqueous hydrochloric acid, maintaining temperature at about 30°C, to decompose any excess sodium borohydride. Add water, warm to about 35°C and add ammonia solution to adjust to approximately pHlO. Separate the aqueous layer and whilst maintaining a temperature of about 35°C, wash the organic layer with water. Distil some of the butanol, whilst simultaneously azeotroping dry the solution. The dry butanol solution is used directly at the next stage. STAGE 5: The preparation offSM-&lt;4-aminobenzvn-2-oxazolidinone·

REACTION

<img img-format="tif" img-content="drawing" file="IL156733AD000220.tif" id="idf0020" />

c14H22n2°3 M.W. 266.34 c10h12n2°2 M.W. 192.21

MATERIALS

QUANTITY

MOLES 15 (£)-£4-Butoxycarbonyi-4-aminophenyialaninol 91.9kg 345.0 n-Butanol 260.0 litres Sodium methoxide (30% weight in methanol 7.5kg 4.7 solution) Charcoal 2.0kg n-Butanol (filter wash) 20.0kg n-Butanol (product wash) 30.0kg Filter aid 2.0kg

PROCEDURE

Charge to the reactor the dry solution of (£)-N-butoxycarbonyl-4-aminophenylalaninol in n-butanol from Stage 4 and add decolourising charcoal. Treat the dry solution at about 8 5 °C with the slow addition of sodium methoxide in methanol. Heat the reaction mixture at 85°C with the slow addition of sodium methoxide in methanol. Heat the reaction mixture at 85°C for a further 30 minutes and then filter hot through filter aid. After cooling the solution at 5-10°C for at least 8 hours, centrifuge the mixture, wash the filtered product with n-butanol and dry at about 50°C in vacuo. STAGE 6A: The preparation of fS)-4-(3-r2-(dimethvlamino)ethvn-1H-indol-5- vPmethvl)-2-oxazolidinone.

REACTION ο

<img img-format="tif" img-content="drawing" file="IL156733AD000221.tif" id="idf0021" />

(I) Sodium nitrite, hydrochloric add -&gt; (II) Sodium sulphite, hydrochloric add

Cl0Hl2N2O2

MW192.2I

Nil 3

HNHjHCL

<img img-format="tif" img-content="drawing" file="IL156733AD000222.tif" id="idf0022" />

KC2,IS°)2C”(C,&lt;2)3N(CII3)2i j » 4,4-4lelhory-N,N-&lt;llmethylbirtylamlne water

Os

MX

<img img-format="tif" img-content="drawing" file="IL156733AD000223.tif" id="idf0023" />

16H21N3°2 &lt;.W. 287.36 l(CII3)2 17 MATERIALS QUANTITY MOLES (S)-4^4.AjninobenzyI)-2-oxa2oHdinone 19.2kg 100.0 Sodium nitrite 6.9kg 100.0 Sodium sulphite 37.8kg 300.0 cone. Hydrochloric acid 66.6kg 4,4-Diethoxy-N1M-dimethylbutyiamine 19.0kg 100.0 32% w/w Sodium hydroxide solution 60.0kg Ethyl acetate (total extracts) 303.0 litres Charcoal 2.9kg Water (demineralised) 412.8kg Ethyl acetate (wash) 10.0 litres Filter aid (total used) 2.0kg

PROCEDURE 18

Charge to the reactor cone, hydrochloric acid, demineralised water and (5)-4-(4-aminobenzyl)-2-oxazolidinone. Cool the reactor contents to between 0-5°C and add aqueous sodium nitrite solution, maintaining the temperature below 5°C. After stirring for about 30 minutes add the diazonium salt solution to a chilled aqueous solution of sodium sulphite, maintaining the temperature below 10°C. After stirring for 15 minutes slowly heat the resulting mixture to about 55-60°C, and then slowly add hydrochloric acid. The solution is maintained at about 60°C for about 18 hours.

Dilute the reaction mixture with water and heat to about 90°C. Under a nitrogen atmosphere slowly add 4t4-diethoxy-N.N-dimethylbutvlamine and heat at reflux for about 3 hours. Cool, and adjust the mixture to about pH7 using sodium hydroxide solution. Extract with ethyl acetate and then adjust the aqueous layer to about pH 10, again using sodium hydroxide solution. Extract the product at about 50°C using ethyl acetate. Treat the combined ethyl acetate extracts (containing the product) with decolourising charcoal, and filter through filter aid. Distil oft most of the solvent and chill the suspension to about 5°C. Centrifuge the crude product, wash with ethyl acetate and vacuum dry at 50°C. STAGE 6B : Purification of fSM-f3-r2-fdimethvlamino)ethvH-lH-indol-5-vHmethvll- 2-oxazolidinone

MATERIALS

QUANTITY

Ethyl acetate

Ethanol

Charcoal

Ethyl acetate (product wash)

Acetone

Water (demineralised)

Water (demineralised) (product wash) Filter acid 109.4 litres 12.3 litres 2.4 kg 5.0 litres 11.8 litres 47.3 kg 10.0 kg 2.0 kg

The crude product of step 6A is dissolved in a refluxing mixture of 10% ethanol in ethyl acetate, treated with decolourising charcoal and filtered hot through filter aid. The 19 solution is slowly cooled to above 5°C and stirred for 18 hours. The purified product is then centrifuged, washed with ethyl acetate and vacuum dried at 50°C. In order to remove solvated ethyl acetate, the dry solid is added to a mixture of 20% acetone in water at ambient temperature and stirred for 1 hour. The suspension is cooled to about 5 °C for about 1 hour before centrifuging the product, washing with ethyl acetate and drying in vacuo at about 45°C.

Example 2

Alternative preparation of Methyl (S)-N-butoxycarbonyl-4-nitrophenylalaninate (Compound of formula (ΠΙ)) A mixture of methyl-4-nitro-(L)-phenylalahinate hydrochloride (40.00g, 0.153 mole) and sodium hydrogen carbonate (73g, 0.870 mole) in 1,4-dioxane (1000ml) was stirred at approximately 10°C under anhydrous conditions. A solution of butyl chloroformate (23.12g, 21.52ml, 0.169 mole) in 1,4-dioxane (200ml) was added over a period often minutes (reaction temperature approximately 13 °C). The resulting suspension was allowed to warm to room temperature and stirred for three hours. The reaction was quenched slowly into water (1600ml) and then extracted with ethyl acetate (3 x 650ml). The combined ethyl acetate extracts weje washed with brine (1000ml), dried over anhydrous magnesium sulphate, filtered and evaporated to an oil. Residual solvent was removed using an oil pump at 50°C to afford a syrup (51.34g, 103% yield) which gradually solidified on standing. TLCfSiO2.EtQAc) was homogeneous (Rf= 0.59). -i-HNMR (60 MHz, CDCI3) was consistent with structure of carbamate.

Example 3

Alternative preparation of Methyl (S)-N-butoxycarbonyl-4-aminophenylaIaninate (Compound of formula (IV)) A solution of the compound prepared by Example 2 [45.00g, 0.139 mole] in ethanol (845mJ) was added to moist 10% palladium on carbon (Type 87L, 61.1% H2O) [-4.5g] 20 under an atmosphere of nitrogen. The reaction was set up for hydrogenation at room temperature under normal atmospheric pressure. There was a steady uptake of hydrogen (-9700ml) over nine hours. The catalyst was filtered off on hyflo and washed with ethanol (100ml). The filtrate was concentrated in vacuo (vnau bath temp. &lt;40°C) and the last traces of solvent removed using an oil pump to afford a brown gum (41.70g, 101%). TLC [SiC&gt;2, EtOAc] showed the required product (Rf - 0.49) with traces of a faster running impurity. lH NMR (300 MHz, CDCI3) was consistent with structure of product and residual ethanol.

Example 4

Alternative preparation of (S)-N-Butoxycarbonyl-4-aminophenyialaninol (Compound of formula (V)).

To a stirred suspension of sodium borohydride (14.80g, 0.390 mole) in SVM (I50mJ), was added dropwise a solution of the compound prepared by Example 3 [76.40g, 0.260 mole) in SVM (460ml) at room temperkture. The reaction was left stirring overnight (-18 hours) after which TLC (SiO2, EtOAc) indicated complete' consumption of starting material. The reaction mixture was acidified to -pH4 with 2M aqueous hydrochloric acid with ice-cooling to a temperature of approximately 10°C. The resulting mixture was concentrated to a solid residue and saturated aqueous sodium hydrogen carbonate (2000ml) was added slowly. The aqueous mixture (pH-8) was extracted with ethyl acetate (2 x 750ml) and the combined organic extracts dried (magnesium sulphate), filtered and concentrated to a pale pink waxy sold (64.56g, 93% yield). TLC [SiO2, EtOAc] indicated the required product (Rf - 0.33) with traces of impurities. ^H NMR (60 MHz, CDCI3) was consistent with structure of alaninol.

The description may contain matter which is not claimed herein but is retained for the sake of completeness. , crrixan rwzn arn pnow pnszn irn nr “|»ob ,Ρ’ηη ηχΰ- πώοβπβ mzrna π^πιώώ np’ioz .zruwan ms rnp’nn pmi1? oxnm □ιηπη Pi? _____88°4003 01 J' ·®O? 08513540200 .(moiB nzrnn) cras&amp;amp;'an nwa