Sunday, 26 June 2016

EP 03031800, New patent, Miglustat, Navinta LLC


Gauchers disease type I; Niemann Pick disease type C
EP-03031800, Process for the preparation of high purity miglustat
Navinta, LLC Shah, Shrenik K. ; Kharatkar, Raju Mahadev ; Bhatt, Chiragkumar Anilkumar ; Kevat, Jitendra Bhagwandas
The present invention provides a process for the preparation and isolation of crystalline miglustat without the use of a column chromatography or ion exchange purification. The crystalline miglustat has a high purity and a melting point of 128 °C and an endothermic peak is 133 °C.
Process for preparing and isolating crystalline form of miglustat with a high purity is claimed. Represents a first PCT filing from the inventors on miglustat. Actelion, under license from Oxford GlycoSciences (OGS; then Celltech, now UCB), which licensed the compound from GD Searle & Co, has developed and launched miglustat.
Product patent WO9426714, will expire in the US in 2018.
Kharatkar is affiliated with Sterling Biotech, Bhatt is affiliated with Intas and Kevat is affiliated with Orchid Chemicals & Pharmaceuticals.
INVENTORS   Shah, Shrenik K.Kharatkar, Raju Mahadev; Bhatt, Chiragkumar Anilkumar; Kevat, Jitendra Bhagwandas
About Navinta
Navinta, LLC in Ewing, N.J. is a technology driven Pharmaceutical Company that focuses on novel routes of synthesis of new and existing drug molecules, complex pharmaceutical ingredients, novel formulations of liquid dosage form, novel oral dosage form, novel injectable dosage form and implantable drug delivery devices. Navinta has currently at least fifteen (15) patents granted or pending with the United States Patent and Trademark Office.

Miglustat is a potent inhibitor of glycosyltransferase. It is primarily used in the treatment of Gaucher's disease. Miglustat is chemically known as N-butyl-1,5-dideoxy-1,5-imino-D-glucitol of formula (I) and is sometimes referred as N-butyl-1-deoxynojirimycin. Miglustat is a white to off-white crystalline solid with a melting point of 125-126° C. Its empirical formula is C10H21NOand has a molecular weight of 219.28 g/mol.
      Miglustat belongs to the class of azasugars or iminosugars. Ever since the discovery of iminosugars in the 1960s, iminosugars have been subject of extensive studies in both the organic chemistry and biochemistry fields. Iminosugars are polyhydroxylated alkaloids, which may be described as monosaccharide analogues with nitrogen replacing oxygen in the ring. A well-known member of this extensive family of compounds is 1-deoxynojirimycin of formula (II).
      1-Deoxynojirimycin was initially synthesized in a laboratory. Subsequently, 1-deoxynojirimycin was isolated from natural sources, such as from leaves of mulberry trees and certain species of bacteria. 1-Deoxynojirimycin was shown to be an enzyme inhibitor.
      Further research on 1-deoxynojirimycin analogs revealed that N-alkylated derivatives of 1-deoxynojirimycin exhibited greater biological activity than 1-deoxynojirimycin. Among them, N-butyl-1-deoxynojirimycin or miglustat of formula (I), was identified as a very potent inhibitor of glycosyltransferase. Miglustat was later approved by the FDA for human use.
      Preparation of azasugars has been a very active area of research for a long time. A seminal synthesis of the compounds of formulas (I) and (II) by double reductive aminations of 5-keto-D-glucose was developed by Baxter and Reitz (J. Org. Chem. 1994, 59, 3175). This method was later refined by Matos and Lopes (Synthesis 1999, 571), in which tetra-O-benzyl-glucose was used as a starting material. Synthesis of miglustat can be traced back to 1977, when chemists from Bayer reported a synthesis of miglustat from 1-deoxynojirimycin and patented in U.S. Pat. No. 4,639,436. Other variations of this general scheme have also appeared in patents and non-patent literature, for example, U.S. Pat. No. 8,802,155 and U.S. Application Publication No. 2014/0243369.
      A major drawback of those protocols is that all of them require the use of ion-exchange resins for purification of miglustat. In those protocols, an aqueous solution of miglustat obtained after running an ion-exchange column was concentrated to isolate miglustat. Due to the presence of four hydroxyl groups and a tertiary amine moiety in its chemical structure, miglustat is extremely hydrophilic. Thus, isolation of miglustat from an aqueous solution is quite challenging. In particular, it was very difficult to remove diastereomers and inorganic impurities formed during the reactions from miglustat by those protocols. Sometimes a second chromatographic purification was required to separate these impurities from miglustat. As a result, the yields of miglustat were generally low. The requirement to use a column purification (e.g. ion exchange column, flash column chromatography) further limits the scale of miglustat that could be prepared.

      Scheme 1 is a synthetic scheme of miglustat in accordance with one embodiment of the invention:
      As depicted in scheme 1, the method of preparing miglustat may include the steps of: (1) providing or synthesizing a compound of formula (V); (2) conducting a reductive amination to provide a compound of formula (VI); (3) performing a hydrogenation reaction; and (4) isolating a free base miglustat.
      The starting material, 2,3,4,6-tetra-O-benzyl-1-deoxynojirimycin hydrochloride of formula (V) may be prepared by following the methods described in Organic Process Research and Development, 2008, 12, 414-423.
Example 1
Synthesis of 2, 3, 4, 6-tetra-O-benzyl-N-butyl-1-deoxynojirimycin hydrochloride of Formula (VI)
To a solution of 2, 3, 4, 6-tetra-O-benzyl-1-deoxynojirimycin hydrochloride (V) (prepared as in Organic Process Research & Development, 2008, 12, 414-423) (45 g, 0.08 mol) in 1575 mL of methanol, n-butyraldehyde (21.6 g, 0.24 mol) and sodium cyanoborohydride (25.2 g, 0.4 mol) were added and stirred. The reaction was maintained under stirring at a temperature from about C. to about C. After the completion of the reaction, the reaction was quenched by adding 765 ml of 10% HCl in methanol, while keeping the temperature between C. to C. The reaction mass was cooled to C. to C. and the resulting precipitate solids were filtered. The filtrate was treated with aqueous HCl and the solid formed was filtered, suspended in 1 N HCl, stirred for 1 hour and filtered. The collected solid was washed with diisopropylether and dried under vacuum to furnish 46.2 g of compound (IV) (46.2 g, 0.075 mol, 94% yield) of high chemical purity based on HPLC analysis (>99.0%).
Example 2
Synthesis of Miglustat Hydrochloride of Formula (III)
A solution of 2, 3, 4, 6-tetra-O-benzyl-N-butyl-1-deoxynojirimycin hydrochloride (VI) (100 g, 0.16 mol) in methanol (1000 mL), 10% HCl solution in methanol (100 mL), and 10% Pd/C (50% wet) (10 g) were mixed and stirred under hydrogen atmosphere at a temperature of about C. to about C. until completion of the reaction. The reaction mass was filtered and the solvent was removed from the filtrate by rotary evaporation. Ethyl acetate (1000 mL) was added to the residue from the rotary evaporation to precipitate the solid. The solid was filtered and dried to isolate Miglustat hydrochloride (III) (42 g, 0.16 mol, 100% yield) of >99.5% purity as measured by HPLC analysis. The DSC thermogram of this product is provided as FIG. 3, and the FTIR spectrum of this product is provided as FIG. 4.
Example 3
Synthesis of Miglustat of Formula (I)
Miglustat hydrochloride (III) (42 g, 0.16 mol) obtained from Example 2 was dissolved in 420 mL of methanol and DBU (1,8-diazabicycloundec-7-ene) (34.1 mL) was added. The reaction mass was warmed slightly and stirred for about 2 hours. The reaction was concentrated by removal of methanol. Dichloromethane (900 mL) was added to the residue. The resulting solid was filtered and dried to obtain crystalline miglustat (I) (27 g, 0.12 mol, 75% yield) of >99.5% purity as measured by HPLC analysis. The melting point of the crystalline miglustat (I) is C. The DSC thermogram and FTIR spectrum of the product are provided as FIG. 1 and FIG. 2, respectively. The crystalline miglustat (I) contained <0.05% of the 5R isomer (IV) as measured by HPLC.

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