FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule l3)
1. TITLE OF THE INVENTION:
PROCESS FOR PREPARATION OF OCTREOTIDE OR INTERMEDIATES THEREOF
2. APPLICANT (S)
(a) NAME: WOCKHARDT LTD.
(b) NATIONALITY: INDIAN
(c) ADDRESS: Wockhardt Towers, Bandra-Kurla Complex, Bandra (East),
Mumbai-400 051.
3. PREAMBLE TO THE DESCRIPTION
The present invention relates to an efficient process for the preparation of octreotide or intermediates thereof.
The following specification particularly describes the invention and the manner
in which it is to be performed.
4. DESCRIPTION
The present invention relates to an efficient process for the preparation of octreotide or intermediates thereof.
Octreotide is a cyclic octapeptide. It is a long-acting octapeptide with pharmacologic properties mimicking those of the natural hormone somatostatin. Octreotide is indicated to reduce blood levels of growth hormone and IGF-I in acromegaly patients. It is also indicated for the symptomatic treatment of patients with metastatic carcinoid tumors and Vasoactive Intestinal Peptide Tumors (VIPomas)
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FORMULA 1
US Patent No 4,395,403 (the '403 Patent) and European Patent EP 029,579 (the '579 Patent) disclose solution synthesis for the preparation of octreotide.
Several solid phase synthesis procedures have been subsequently described viz. European Patent No EP 953,577 and U.S. Pat. No 5,889,146 and in various research publications. Mergler et al (Proceedings of the 12.sup.th American Peptide Symposium) have used aminomethyl resin and Fmoc-butyl protection scheme for synthesis of octreotide. Alsina et at (Tetrahedron Letters, 38, 883, 1997) have used an active carbonate resin and Boc-Bzl protection scheme, necessitating the use of hydrogen fluoride/anisole for final deprotection. Edwards et al (J. Med. Chem., 37, 3749, 1994) have described another synthesis using Fmoc-butyl protection and HMP resin, and Berta et al (European Patent EP 953, 577) described a synthesis using 2-chlorotrityl-type resin and Fmoc-butyl protection scheme.
All the solid phase synthesis procedures described are not suitable for commercial manufacture of octreotide because they use costly resins and costly Fmoc-butyl protected amino acids in 2 to 4 times excess at every step. Some synthesis procedures use destructive and hazardous reagents for final deprotection.
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The present inventors now found out an efficient process for the preparation of octreotide or intermediates thereof. The present invention has the advantages of reduced process time, low ratio of reactants, lowered cost, enhanced yield and purity, easy purification and applicability for large-scale production.
In one of the aspects of the present invention there is provided a process for preparation of L-Thr-OMe wherein the said process comprises of
a) treating L-Thr-OH with methanol and thionyl chloride at a temperature above 45°C,
b) removing excess thionyl chloride from the reaction mass,
c) isolating L-Thr-OMe from the reaction mass thereof.
L-Thr-OH can be prepared by the procedure, which is well known to those skilled in the art. Commercially available raw material can also be employed. Treatment of L-Thr-OH with methanol and thionyl chloride at a temperature above 45°C facilitates the rate of reaction and thus it requires less time resulting in the good yield and good quality of the product. The earlier known processes operate on low temperatures and therefore are time consuming and do not go to completion.
In another aspect of the invention there is provided a process for removal of inorganic impurities (de-salting) of Ri-Cys(Acm)-Thr-OL, wherein Ri is amino or suitable amino protecting group used in peptide chemistry, wherein the said process comprises of
a) reducing Ri-Cys(Acm)-Thr-OMe in presence of suitable organic solvent and sodium borohydride,
b) extracting the resultant mass in dichloromethane,
c) isolating Ri-Cys(Acm)-Thr-OL from the extract thereof.
Ri-Cys(Acm)-Thr-OMe can be prepared by the procedure which is well known to those skilled in peptide chemistry. According to the prior art, in case of Ri-Cys(Acm)-Thr-OL dipeptide purification, desalting was carried out with the help of
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HPLC followed by collection of desired product in the form of aqueous solution; this aqueous solution was further lyophilized to get the resultant mass. This process takes about 40 hours. The present inventors now found out that, when desalting was carried out by extracting the resultant mass in dichloromethane, all the undesired inorganic salts remain in aqueous solution and the desired product component gets selectively extracted in the organic phase, which is then isolated in purified form. Thus there is no need of lyophilization, which saves time, and product quality and yield has also improved.
The intermediates thus obtained as part of this invention can be converted to octreotide or salt thereof by processes known in the art.
While the present invention has been described in terms of its specific embodiments, certain modifications and equivalents will be apparent to those skilled in the art and are intended to be included within the scope of the present
invention.
Example 1
Preparation of L-Thr-OMe. HCI
The amino acid H-Thr-OH (35.7 g) was added in portions to methanol (200 ml) and thionyl chloride (109.2 ml) under stirring at temperature 10-20°C. After complete addition, reaction mass was re fluxed till the reaction was complete as monitored by TLC. The reaction mixture is evaporated under vacuum at 45 °C. Ether (100 ml x 3) was added to the residue and triturated it. The precipitated solids were filtered and dried under vacuum at 40 °C for 1 hour. Yield = 50 g Calculated mass = 133 Obtained mass = 134
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Example 2 Preparation of Boc-Cys (Acm)-Thr-OL
Sodium borohydride (14 g) was added to a solution of Boc-Cys (Acm)-Thr-OMe (75.4 g) in aqueous ethanol (452.4 ml, 90%) at 5°C. The stirring was continued for further about 2 hours till the reaction was complete as monitored by HPLC. Reaction mass was slowly added to aqueous acetic acid (942.5 ml, 4% w/w) under stirring at 5°C. The reaction mixture was saturated with sodium chloride and extracted in dichloromethane (3 x 500 ml). Dichloromethane layer was dried on sodium sulfate and concentrated under vacuum to get the desired product as syrupy oil. Yield =70 g
Calculated Mass = 379 Obtained Mass = 380.3
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WE CLAIM:
1. A process for preparation of L-Thr-OMe wherein the said process comprises of
a) treating L-Thr-OH with methanol and thionyl chloride at a temperature above 45°C,
b) removing excess thionyl chloride from the reaction mass,
c) isolating L-Thr-OMe from the reaction mass thereof.

2. A process according to claim 1 wherein the temperature is 60°C or above.
3. A process for removal of inorganic impurities (de-salting) of RrCys(Acm)-Thr-OL, wherein Ri is amino or suitable amino protecting group used in peptide chemistry, wherein the said process comprises of

a) reducing Ri-Cys(Acm)-Thr-OMe in presence of suitable organic solvent and sodium borohydride,
b) extracting the resultant mass in dichloromethane,
c) isolating Ri-Cys(Acm)-Thr-OL from the extract thereof.

4. A process for preparation of octreotide or salt thereof comprising process of claim 1.
5. A process for preparation of octreotide or salt thereof comprising process of claim 3.
Dated this-28th day of March, 2006

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