DESC:FIELD OF THE INVENTION:

The present invention relates to enzymatic process for the preparation of (S)-3-(methyl-
1-phenylethyl)amino)-1-(thiophen-2-yl)propan-1-ol (Compound of formula 7).

Formula 7

BACKGROUND OF THE INVENTION:

Duloxetine hydrochloride is chemically known as (S)-(+)-N-methyl-3-(1-naphthyloxy)-3-(2-thienyl)propanamine hydrochloride, the structure of formula (1).

Duloxetine is disclosed in U.S. patent No. 4,956,388 and its acid addition salts in U.S.patent No. 5,362,886. Duloxetine is a serotonin and norepinephrine re-uptake dual inhibitor and a highly efficient antidepressant agent for treating psychiatric disorders. It is marketed under the brand name Cymbalta® in USA.

The U.S. patent No. 7,538,232 describes preparation of duloxetine by arylation of (S)-3-(methylamino)-1-(thiophen-2-yl)propan-1-ol (2) with 1-fluoronaphathalene (3) in the presence of potassium hydroxide as base and dimethyl sulfoxide as solvent. This arylation reaction results into the complete racemization to give 1:1 mixture of duloxetine and (R)-(-)-N-methyl-3-(1-naphthyloxy)-3-(2-thienyl)propanamine (i.e. R-isomer). The racemization was minimized to obtain duloxetine containing R isomer upto 1% by using mixture of dimethyl sulfoxide and toluene as solvent. However, the use of mixed organic solvents has disadvantageous in view of environmental protection and high cost due to solvent recovery.

The U.S. patent No. 8,530,674 describes preparation of duloxetine containing R-isomer upto 2.5% by arylation of (S)-3-(methylamino)-1-(thiophen-2-yl)propan-1-ol (2) with 1-fluoronaphathalene (3) in the presence of potassium tert-butoxide as base and dimethyl sulfoxide as solvent. Duloxetine obtained by this process requires further purification to get chiral pure duloxetine.

The PCT application WO2010/025287 describes preparation of ketoreductase polypeptides for the production of 3-aryl-3-hydroxypropanamine from a 3-aryl-3-ketopropanamine.

Present invention has developed an enzymatic process for the preparation of (S)-3-(methyl-1-phenylethyl) amino)-1-(thiophen-2-yl) propan-1-ol (Compound of formula 7).

SUMMARY OF THE INVENTION:

The present invention relates to an enzymatic process for the preparation of (S)-3-(methyl-1-phenylethyl) amino)-1-(thiophen-2-yl) propan-1-ol (Compound of formula 7).

Formula 7

The present invention also provides a process for the preparation of (S)-3-(methyl-1-phenylethyl) amino)-1-(thiophen-2-yl) propan-1-ol comprising;
a) contacting the compound of formula 6 with one or more ketoreductase enzymes (specifically codexis enzymes)

b) isolating pure (S)-3-(methyl-1-phenylethyl) amino)-1-(thiophen-2-yl) propan-1-ol.

DETAILED DESCRIPTION OF THE INVENTION:

One aspect of the present invention to provide an enzymatic process for the preparation of (S)-3-(methyl-1-phenylethyl)amino)-1-(thiophen-2-yl)propan-1-ol (Compound of formula 7).

Formula 7

Yet another aspect of the present invention to provide a process for the preparation of (S)-3-(methyl-1-phenylethyl)amino)-1-(thiophen-2-yl)propan-1-ol (Compound of formula 7) comprising the steps of;
a) contacting the compound (S)-3-(methyl(1-phenylethyl)amino)-
1-(thiophen-2-yl)propan-1-one (formula 6) with one or more ketoreductase enzymes (specifically codexis enzymes)
b) isolating pure (S)-3-(methyl-1-phenylethyl) amino)-1-(thiophen-2-yl)propan-1-ol (Compound of formula 7)
c) Optionally converting to duloxetine or its salts thereof.

Another aspect of the present invention provides an enzymatic process for the preparation of compound of Formula 7 is depicted in following scheme-1;

According to the present invention, wherein compound of formula 6 can be obtained by the process known in Indian patent application IN0303/MUM/2015.

According to the present invention, wherein reacting compound of formula 6 with codexis enzymes selected from one or more are given in below table-A;
Table-A
Sr.No. Enzyme code Enzyme supplier

1 KRED-P1-B10 Codexis
2 KRED-P1-B12 Codexis
3 KRED-P1-C01 Codexis
4 KRED-P1-H08 Codexis
5 KRED-P2-B02 Codexis
6 KRED-P2-D03 Codexis
7 KRED-P2-D11 Codexis
8 KRED-P2-D12 Codexis
9 KRED-P2-H07 Codexis
10 CDX-022 Codexis
13 CDX-008 Codexis
14 CDX-021 Codexis
15 KRED-101 Codexis
16 KRED-NADH-110 Codexis
17 KRED-P1-B02 Codexis
18 KRED-P1-B05 Codexis
19 KRED-P2-C02 Codexis
20 KRED-P2-G03 Codexis
21 KRED-P2-C11 Codexis

According to the present invention, wherein the reaction is carried at a temperature 15-45°C, preferably from about 20 to 30°C.

The process of the present invention has following advantages:
i. Provides specific (S)-isomer with 99.5 to 100% (by HPLC)
ii. Provides higher yields of product with high purity,
iii. Reaction is involved at room temperature,

The present invention is described in the following example, however it should be noted that the scope of present invention is not limited by the example.

Examples:

Example-1: Process for the preparation of (S)-3-(methyl-1-phenylethyl) amino)-1-(thiophen-2-yl) propan-1-ol (Compound of formula 7):

(S)-3-(methyl(1-phenylethyl)amino)-1-(thiophen-2-yl)propan-1-one (10 g) was dissolved in 30 ml of Isopropyl alcohol and 60 ml of buffer solution (0.2 M potassium phosphate buffer, pH 7.00, 2mM MgSO4). The reaction was initiated by adding an enzyme solution (Codexis enzymes are given in below table & 0.1 mg NAD was dissolved in 10 ml buffer) into the above mixture. The reaction mixture was stirred at 25-350C for 24 hrs. After completion of reaction, distilled off solvent to obtain the desired compound of formula 7.
Yield: 9.85 g
Table B: above example was screened with specific codexis enzymes and the results are mentioned below;
Sr.No. Enzyme code Enzyme supplier % Conversion Chiral purity
R-Isomer (Undesired) S-Isomer (Desired)
1 KRED-P1-B10 Codexis 100% - 100%
2 KRED-P1-B12 Codexis 100% - 100%
3 KRED-P1-C01 Codexis 100% - 100%
4 KRED-P1-H08 Codexis 100% - 100%
5 KRED-P2-B02 Codexis 100% 11.07% 88.93%
6 KRED-P2-D03 Codexis 100% - 100%
7 KRED-P2-D11 Codexis 100% - 100%
8 KRED-P2-D12 Codexis 100% - 100%
9 KRED-P2-H07 Codexis 100% - 100%
10 CDX-022 Codexis 100% 11.42% 88.58%
13 CDX-008 Codexis 00 NA NA
14 CDX-021 Codexis 100% - 100%
15 KRED-101 Codexis 100% 19.04% 80.96%
16 KRED-NADH-110 Codexis 100% - 100%
17 KRED-P1-B02 Codexis 100% - 100%
18 KRED-P1-B05 Codexis 100% - 100%
19 KRED-P2-C02 Codexis 98.77% - 100%
20 KRED-P2-G03 Codexis 100% - 100%
21 KRED-P2-C11 Codexis 100% - 100%

,CLAIMS:1. A process for the preparation of (S)-3-(methyl-1-phenylethyl)amino)-1-(thiophen-2-yl)propan-1-ol (Compound of formula 7) comprising;
a) contacting the compound (S)-3-(methyl (1-phenylethyl) amino)-
1-(thiophen-2-yl) propan-1-one (formula 6) with one or more ketoreductase enzymes (specifically codexis enzymes)
b) isolating pure (S)-3-(methyl-1-phenylethyl) amino)-1-(thiophen-2-yl)propan-1-ol (Compound of formula 7)
c) Optionally converting to duloxetine or its salts thereof.

2. The process according to claim 1, step a wherein the ketoreductase enzymes are selected from following Table C:
Table C

Sr.No. Enzyme code Enzyme supplier

1 KRED-P1-B10 Codexis
2 KRED-P1-B12 Codexis
3 KRED-P1-C01 Codexis
4 KRED-P1-H08 Codexis
5 KRED-P2-B02 Codexis
6 KRED-P2-D03 Codexis
7 KRED-P2-D11 Codexis
8 KRED-P2-D12 Codexis
9 KRED-P2-H07 Codexis
10 CDX-022 Codexis
13 CDX-008 Codexis
14 CDX-021 Codexis
15 KRED-101 Codexis
16 KRED-NADH-110 Codexis
17 KRED-P1-B02 Codexis
18 KRED-P1-B05 Codexis
19 KRED-P2-C02 Codexis
20 KRED-P2-G03 Codexis
21 KRED-P2-C11 Codexis

3. The process according to claim 1, step b wherein the (S)-3-(methyl-1-phenylethyl) amino)-1-(thiophen-2-yl) propan-1-ol (Compound of formula 7) having a purity 99.5% by HPLC.