Patent Description:
Isavuconazonium sulfate is a prodrug of the broad spectrum azole antifungal agent isavuconazole. It is being commercialised for the treatment of aspergillosis and mucormycosis and is available as oral and intravenous formulations. Isavuconazonium salts are described in <CIT> and a method for preparing isavuconazonium hydrochloride is given in Example <NUM>. However, due to its sensitivity to moisture, isavuconazonium salts such as the commercial product isavuconazonium sulfate, are difficult to purify from crude material in high yield.

Attempts have been made to purify isavuconazonium sulfate by crystallisation. For example, <CIT> describes methods of preparing a crystal form of isavuconazonium sulfate. The method involves step <NUM>: dissolving isavuconazole hydrochloride in water, adjusting the pH to neutral using a base at a low temperature, adding an organic solvent A for extraction, drying and concentrating and then dissolving in an organic solvent B, adding concentrated sulfuric acid and hydrogen peroxide at a low temperature, stirring, and concentrating; step <NUM>: adding the abovementioned concentrate to an organic solvent C, heating to dissolve, stirring and cooling to crystallize, and performing suction filtration to obtain a crystal. This method is however not suitable for commercial scale-up. In particular the use of hydrogen peroxide leads to significant degradation of the product.

<CIT> also describes methods of preparing a crystal form of isavuconazonium sulfate. The method involves (a) dissolving the crude isavuconazonium sulphate product in a mixed solution of water, an organic solvent A and an organic solvent B, (b) dropwise adding an organic solvent C to the isavuconazonium sulphate solution obtained in step (a); and (c) performing stirring crystallization and separation to obtain said isavuconazonium sulphate compound, wherein the organic solvent A refers to R1-O-CH2-CH2OH; the organic solvent B refers to R2-C(=O)-R3 and/or tetrahydrofuran; and the organic solvent C refers to R4-C(=O)O-R5; R1, R2, R3, R4 and R5 being independently selected from C1-<NUM> alkyl.

However, as shown in the Comparative Examples below we have found that the method described in <CIT> results in low yield when the crude material is of lower purity. In addition when starting from high purity material <CIT> produces a isavuconazonium sulfate product which is highly enriched for one of the two epimers, whereas the approved commercial product has a molar epimer ratio of <NUM>:<NUM> to <NUM>:<NUM>.

The two epimers of isavuconazonium are depicted here:
<CHM>.

The present invention provides new procedures for the purification of isavuconazonium sulfate, referred to herein as the sulfate salt of the compound of formula I.

In a first aspect the invention provides a method for purifying the sulfate salt of the compound of formula I
<CHM>
comprising the steps of.

The epimers of the sulfate salt of the compound of formula I are defined herein by reference to their retention times. Epimer A is the first epimer to elute from a chiral HPLC column functionalized with phenylcarbamated β-cyclodextrin in which the mobile phase is a mixture of triethylammonium acetate and acetonitrile in proportions <NUM>:<NUM> at pH <NUM>.

Generally the mixture provided in step (a) comprises a mixture of epimer A and epimer B of the sulfate salt of the compound of formula I, usually in similar amounts. The portions obtained from step (b) and step (c) contain different proportions of epimer A and epimer B. Step (b) selectively crystallizes epimer B, whilst step (c) is effective for precipitating epimer A remaining in the solution. Thus, in the absence of step (c) the resulting crystalline form from step (b) will tend to be of lower yield because a large portion of epimer A will still be in solution. In addition, for this reason the ratio of epimers will usually not correspond to the ratio required for commercialization, namely a ratio of <NUM>:<NUM> to <NUM>:<NUM>. When step (c) is included, a larger proportion of epimer A precipitates, which may allow a resulting ratio of epimer A to epimer B within the limits required for the commercial product.

The molar ratio of epimer B to epimer A in the portion of the sulfate salt of the compound of formula I obtained from step (b) is generally greater than <NUM>:<NUM>, e.g. at least <NUM>:<NUM>, e.g. at least <NUM>:<NUM>, e.g. at least <NUM>:<NUM>, e.g. at least <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM> e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>.

The molar ratio of epimer A to epimer B in the portion of the sulfate salt of the compound of formula I obtained from step (c) is generally greater than <NUM>:<NUM>, e.g. at least <NUM>:<NUM>, e.g. at least <NUM>:<NUM>, e.g. at least <NUM>:<NUM>, e.g. at least <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM> e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>.

The molar ratio of epimer A to epimer B in the combined portions of the sulfate salt of the compound of formula I from step (b) and step (c) taken together may be <NUM>:<NUM> to <NUM>:<NUM>, e.g. about <NUM>:<NUM> to about <NUM>:<NUM>.

The mixture provided in step (a) may be prepared from the solid crude product obtained from the synthesis of the sulfate salt of the compound of formula I, which may be synthesized by the person skilled in the art according to known procedures. In one embodiment the precursor to the compound of formula I is the sulfate salt of the Boc protected analogue of the compound of formula I (compound <NUM> as depicted in <CIT>), which may be deprotected using sulfuric acid using a suitable solvent, e.g. ethylacetate, e.g. at a temperature in the range of <NUM> to <NUM>, to give the sulfate salt of the compound of formula I. This may be allowed to precipitate, e.g. in water, to give solid crude product, which may optionally be washed, e.g. with a protic organic solvent such as isopropanol.

Solid crude product will contain impurities formed during the synthesis of the sulfate salt of the compound of formula I. The purity of the sulfate salt of the compound of formula I in the solid crude product which may be used in step (a) is usually e.g. (before or after washing) at least <NUM>% (i.e. the weight amount of the sulfate salt of the compound of formula I relative to the weight amount of impurities), e.g. in the range of <NUM>% to <NUM>%, e.g. in the range of <NUM>% to <NUM>%, e.g. in the range of <NUM>% to <NUM>%, e.g. in the range of <NUM>% to <NUM>%, e.g. in the range of <NUM>% to <NUM>%, e.g. in the range of <NUM>% to <NUM>%, e.g. in the range of <NUM>% to <NUM>%, e.g. in the range of <NUM>% to <NUM>%, e.g. in the range of <NUM>% to <NUM>%. In other embodiments the purity of the sulfate salt of the compound of formula I in the solid crude product which may be used in step (a) may be no more than <NUM>%, e.g. no more than <NUM>%, e.g. no more than <NUM>%, no more than <NUM>%.

The mixture of step (a) may be provided by dissolving the solid crude product of the sulfate salt of the compound of formula I in the aliphatic alcohol. An aliphatic moiety is a non-aromatic hydrocarbon moiety in which the constituent carbon atoms can be straight-chain, branched chain, or cyclic. Aliphatic alcohols according to the invention contain one or two OH groups, providing that when there are two OH groups there are three to six carbon atoms in the aliphatic moiety. The aliphatic alcohol may be C2-C10alkyl-OH or C3-C10cycloalkyl-OH (e.g. cyclopentanol, cyclohexanol, cycloheptanol) or a mixture thereof, in particular C2-C10alkyl-OH. In one embodiment the aliphatic alcohol is an aliphatic alcohol selected from ethanol, propanol (including any isomer thereof e.g. propan-<NUM>-ol, isopropanol), butanol (including any isomer thereof, e.g. n-butan-<NUM>-ol, n-butan-<NUM>-ol, t-butan-<NUM>-ol, t-butan-<NUM>-ol), and pentanol (including any isomer thereof) or a mixture thereof. In another embodiment the aliphatic alcohol is propanol or ethanol or a mixture thereof. In another embodiment the aliphatic alcohol is ethanol or n-butanol. In another embodiment the aliphatic alcohol is ethanol.

The v/w ratio (i.e. milliliters: grams) of the aliphatic alcohol to the sulfate salt of the compound of formula I may be up to <NUM>:<NUM> e.g. up to <NUM>:<NUM>, e.g. up to <NUM>:<NUM>, e.g. up to <NUM>:<NUM>, e.g. up to <NUM>:<NUM>, e.g. up to <NUM>:<NUM>, e.g. up to <NUM>:<NUM>, e.g. up to <NUM>:<NUM>, e.g. at least <NUM>:<NUM>, e.g. at least <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM> e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. about <NUM>:<NUM>. For example the v/w ratio of ethanol to the sulfate salt of the compound of formula I may be up to <NUM>:<NUM>, e.g. up to <NUM>:<NUM>, e.g. up to <NUM>:<NUM>, e.g. up to <NUM>:<NUM>, e.g. up to <NUM>:<NUM>, e.g. up to <NUM>:<NUM>, e.g. up to <NUM>:<NUM>, e.g. up to <NUM>:<NUM>, e.g. at least <NUM>:<NUM>, e.g. at least <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>: <NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM> e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. about <NUM>:<NUM>.

Optionally the mixture in step (a) comprises water in addition to the aliphatic alcohol. The v/v ratio of the aliphatic alcohol to water may be up to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. about <NUM>:<NUM>. For example, the v/v ratio of ethanol to water may be up to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. in the range of <NUM>:<NUM> to <NUM>:<NUM>, e.g. about <NUM>:<NUM>.

In one embodiment the mixture of step (a) is provided by obtaining solid crude product comprising the sulfate salt of the compound of formula I and dissolving the solid crude product in the aliphatic alcohol and optionally water.

Dissolution of solid crude product in the aliphatic alcohol and optionally water may result in a pH which is lower than that desired due to the presence of excess sulfuric acid. When adjusting the pH it will usually be preferable to avoid the use of inorganic bases as they may lead to decomposition of the product. Alternative ways of adjusting, e.g. increasing, the pH include the use of anion exchange resins such as weak base anion exchange resins, which are commercially available, e.g. from Amberlite®. In one embodiment the pH of the mixture in step (a) is provided to be about pH <NUM> to about pH <NUM>, e.g. about pH <NUM> to about pH <NUM>. in another embodiment the pH is provided to be about pH <NUM> to about pH <NUM>. In another embodiment the pH is provided to be about pH <NUM> to about pH <NUM>. In another embodiment the pH is provided to be about pH <NUM> to about pH <NUM>. In another embodiment the pH is provided to be about pH <NUM> to about pH <NUM>. In another embodiment the pH is provided to be about <NUM>. Generally the pH is increased to a value such that the mixture does not turn into an oil, but is not too high such that the sulfate salt of the compound of formula I becomes too soluble.

Generally solid crude product will be dissolved in the aliphatic alcohol (and optionally water) at a suitable temperature which is high enough to achieve dissolution, but not too high such that the compound of formula I decomposes, e.g. by hydrolysis. For example the dissolution temperature may be in the range of -<NUM> to <NUM>, e.g. in the range of <NUM> to <NUM>, e.g. in the range of <NUM> to <NUM>, e.g. in the range of <NUM> to <NUM>, e.g. at least -<NUM>, e.g. at least <NUM>, e.g. at least <NUM>, e.g. up to <NUM>, e.g. up to <NUM>, e.g. up to <NUM>, e.g. up to <NUM>. The mixture may be allowed to remain at these temperatures for up to <NUM> hours, e.g. up to <NUM> hours, e.g. up to <NUM> hours, e.g. in the range of <NUM> to <NUM> hours, e.g. in the range of <NUM> to <NUM> hours, e.g. in the range of <NUM> to <NUM> hours, and may be stirred during this period.

Step (b) may comprise allowing a first portion of the sulfate salt of the compound of formula I to crystalize from the mixture by cooling the mixture. For example, the mixture may be cooled from the starting temperature (e.g. the dissolution temperature) to a temperature in the range of -<NUM> to <NUM> (e.g. at least -<NUM>, e.g. up to <NUM>), e.g. in the range of -<NUM> to <NUM> (e.g. at least -<NUM>, e.g. up to <NUM>), e.g. in the range of <NUM> to <NUM> (e.g. at least <NUM>, e.g. up to <NUM>), e.g. to a temperature in the range of <NUM> to <NUM> (e.g. at least <NUM>, e.g. up to <NUM>), e.g. to a temperature of about <NUM>. The starting temperature (e.g. the usually the dissolution temperature) may be a temperature in the range of <NUM> to <NUM> (e.g. at least <NUM>, e.g. up to <NUM>), e.g. in the range of <NUM> to <NUM> (e.g. at least <NUM>, e.g. up to <NUM>), e.g. in the range of <NUM> to <NUM> (e.g. at least <NUM>, e.g. up to <NUM>). The period during which the mixture is cooled may be for example <NUM> minutes to <NUM> hours, e.g. in the range of <NUM> to <NUM> hours, e.g. in the range of <NUM> to <NUM> hours, bearing in mind that prolonged periods at higher temperatures can lead to decomposition.

Examples of rates of cooling which may be used are for example not more than <NUM> per hour, e.g. not more than <NUM>, e.g. not more than <NUM> per hour, e.g. not more than <NUM> per hour, e.g. in the range of <NUM> to <NUM> per hour, e.g. in the range of <NUM> to <NUM> per hour, e.g. about <NUM> per hour.

In step (b) the the mixture may be allowed to stand for a suitable period, e.g. up to <NUM> days, e.g. in the range of <NUM> to <NUM> days, at a temperature in the range of -<NUM> to <NUM> (e.g. at least -<NUM>, e.g. up to <NUM>), e.g. in the range of <NUM> to <NUM> (e.g. at least <NUM>, e.g. up to <NUM>), e.g. about <NUM>. Longer standing periods, e.g. at least <NUM> days, e.g. in the range of <NUM> to <NUM> days, e.g. in the range of <NUM> to <NUM> days, may allow an increase in yield, whilst avoiding oily products. The period during which the mixture is allowed to stand may be reduced by adding seed crystals.

In step (c) the aprotic organic solvent may be C4-C10alkyl, or C4-C10alkenyl or a mixture thereof. Specific examples include hexane and heptane or a mixture thereof, such as n-hexane or n-heptane or a mixture thereof. In one embodiment the aprotic solvent is n-heptane. Other specific examples include hexene and heptene, such as <NUM>-hexene or <NUM>-heptene. In another embodiment the aprotic solvent is <NUM>-hexene.

The volume of aprotic organic solvent used in step (c) may be up to <NUM> times, e.g. up to <NUM> times, e.g. up to <NUM> times, e.g. at least <NUM> times, e.g. at least <NUM> times, e.g. at least <NUM> times, e.g. at least <NUM> times, e.g. at least <NUM> times the volume of the mixture in step (a), e.g. in the range of <NUM> to <NUM> times the volume of the mixture in step (a), e.g. in the range of <NUM> to <NUM> times, e.g. in the range of <NUM> to <NUM> times, e.g. in the range of <NUM> to <NUM> times, e.g. in the range of <NUM> to <NUM> times the volume of the mixture in step (a).

The aprotic organic solvent may be added to the mixture over a suitable period e.g. in the range of <NUM> minutes to <NUM> hours, e.g. in the range of <NUM> to <NUM> hours, e.g. in the range of <NUM> to <NUM> hours. The temperature during this period may be in the range of -<NUM> to <NUM> (e.g. at least -<NUM>, e.g. up to <NUM>), e.g. in the range of <NUM> to <NUM> (e.g. at least <NUM>, e.g. up to <NUM>), e.g. about <NUM>. The mixture may be stirred during this period.

Following addition of the aprotic solvent the mixture may be allowed to stand for a suitable period of time, e.g. up to <NUM> days, e.g. in the range of <NUM> hour to <NUM> days, e.g. at a temperature in the range of -<NUM> to <NUM> (e.g. at least -<NUM>, e.g. up to <NUM>), e.g. in the range of <NUM> to <NUM> (e.g. at least <NUM>, e.g. up to <NUM>), e.g. about <NUM>. The product may be dried.

Step (a) may comprise providing a mixture comprising the sulfate salt of the compound of formula I and ethanol and optionally water, and step (c) may comprise adding propanol (including any isomer thereof e.g. propan-<NUM>-ol, isopropanol) and/or butanol (including any isomer thereof, e.g. n-butan-<NUM>-ol, n-butan-<NUM>-ol, t-butan-<NUM>-ol, t-butan-<NUM>-ol), preferably isopropanol, and an aprotic organic solvent selected from hexane and heptane and a mixture thereof, preferably n-heptane, to the mixture and allowing an additional portion of the sulfate salt of the compound of formula I to precipitate from the mixture. The propanol and/or butanol may be added to the mixture prior to the aprotic organic solvent and following addition of the propanol and/or butanol the mixture may be allowed to stand prior to adding the aprotic organic solvent, e.g. to allow a portion of the sulfate salt of the compound of formula I to precipitate from the mixture prior to adding the aprotic solvent.

According to an embodiment, the invention provides a method for purifying the sulfate salt of the compound of formula I comprising the steps of:.

The propanol and/or butanol may be added to the mixture over a period in the range of <NUM> minutes to <NUM> hours, e.g. in the range of <NUM> to <NUM> hours, e.g. in the range of <NUM> to <NUM> hours. The temperature during this period may be in the range of -<NUM> to <NUM> (e.g. at least -<NUM>, e.g. up to <NUM>), e.g. in the range of <NUM> to <NUM> (e.g. at least <NUM>, e.g. up to <NUM>), e.g. about <NUM>. The mixture may be stirred during this period. Following additional of propanol and/or butanol the mixture may be allowed to stand for a suitable period of time prior to adding the aprotic solvent, e.g. up to <NUM> days, e.g. <NUM> hour to <NUM> days, e.g. at a temperature in the range of -<NUM> to <NUM> (e.g. at least -<NUM>, e.g. up to <NUM>), e.g. in the range of <NUM> to <NUM> (e.g. at least <NUM>, e.g. up to <NUM>), e.g. about <NUM>.

The volume of propanol and/or butanol may be may be up to <NUM> times, e.g. up to <NUM> times, e.g. up to <NUM> times the volume of the mixture in step (a), e.g.at least <NUM> times, e.g. at least <NUM> times, e.g. at least <NUM> times, e.g. at least <NUM> times, e.g. in the range of <NUM> to <NUM> times, e.g. in the range of <NUM> to <NUM> times, e.g. in the range <NUM> to <NUM> times, e.g. in the range of <NUM> to <NUM> times the volume of the mixture in step (a).

The v/v ratio of the aprotic organic solvent to propanol and/or butanol may be e.g. <NUM>:<NUM> to <NUM>:<NUM>, e.g. <NUM>:<NUM> to <NUM>:<NUM>, e.g. <NUM>:<NUM> to <NUM>:<NUM>.

According to an embodiment, the invention provides a method for purifying the sulfate salt of the compound of formula I comprising the steps of.

In a further aspect the invention provides a method for preparing epimer B of the sulfate salt of the compound of formula I in crystalline form, wherein epimer B is the second epimer of the epimers
<CHM>
to elute from a chiral HPLC column functionalized with phenylcarbamated β-cyclodextrin in which the mobile phase is a mixture of triethylammonium acetate and acetonitrile in proportions <NUM>:<NUM> at pH <NUM>, comprising the steps of.

The above description of steps (a) and (b) in relation to the first aspect of the invention also apply to steps (a) and (b) in this aspect of the invention where possible.

In a further aspect the invention provides a method for preparing epimer A of the sulfate salt of the compound of formula I in solid form, wherein epimer A is the first epimer of the epimers
<CHM>
to elute from a chiral HPLC column functionalized with phenylcarbamated β-cyclodextrin in which the mobile phase is a mixture of triethylammonium acetate and acetonitrile in proportions <NUM>:<NUM> at pH <NUM>, comprising the step of.

The above description of step (c) (including the description of step (c) as steps (c1) and (c2)) in relation to the first aspect of the invention also apply to step (c) in this aspect of the invention where possible.

In a further aspect the invention provides a method for preparing a pharmaceutical composition comprising (i) purifying the sulfate salt of the compound of formula I by a method as described herein and (ii) formulating the sulfate salt of the compound of formula I with one or more pharmaceutical excipients.

Pharmaceutical compositions comprising the sulfate salt of the compound of formula I may be prepared according to the common general knowledge of the person skilled in the art using routinely available pharmaceutical excipients. The pharmaceutical formulation may be a powder for injection or a capsule for oral administration. For example, isavuconazonium sulfate is commercially available as a lyophilised powder for intravenous administration, containing the excipients mannitol and sulfuric acid for pH adjustment and as a capsule for oral administration containing the excipients trimagnesium dicitrate, microcrystalline cellulose, talc, colloidal silica dioxide and stearic acid.

The sulfate salt of the compound of formula I purified as described herein may be formulated directly into a pharmaceutical composition or may undergo further processing steps before being formulated into a pharmaceutical composition. For example it may be re-precipitated e.g. to produce an amorphous form, e.g. as used in the approved formulation for oral administration. For example it may be dissolved in a suitable solvent and lyophilised, e.g. as used in the approved formulation for injection.

Alkyl and alkenyl groups may be linear or branched. The term "about" indicates a variation of +/- <NUM>% of the given value, preferably <NUM>%, more preferably <NUM>%. All ranges mentioned include the starting point and the end point of the specified range. All aspects and embodiments of the invention described herein may be combined in any combination where possible.

Particular embodiments of the invention are described in the following Examples, which serve to illustrate the invention in more detail and should not be construed as limiting the invention in any way.

<NUM> of the crude sulfate salt of the compound of formula I, HPLC purity <NUM>%, was dissolved in a mixture of <NUM> ethanol and <NUM> water, the pH value of the solution was <NUM>. Then the resulting solution was cooled to -<NUM> from <NUM> (-<NUM> per hour). The mixture was stirred at -<NUM> over <NUM> hours and then warmed to <NUM>. The mixture was then stirred at <NUM> over <NUM> hours. After filtration and drying <NUM> of the sulfate salt of the compound of formula I was obtained as white crystalline Form I with <NUM>% HPLC purity in <NUM>% yield (epimer ratio not determined).

<NUM> of the crude sulfate salt of the compound of formula I, HPLC purity <NUM>%, was dissolved in a mixture of <NUM> ethanol and <NUM> water, pH <NUM>, and stirred at <NUM> over <NUM> days. After filtration and drying <NUM> of the sulfate salt of the compound of formula I was obtained as white crystalline Form I with <NUM>% HPLC purity in <NUM>% yield (epimer ratio not determined).

<NUM> of the crude sulfate salt of the compound of formula I, HPLC purity <NUM>%, was dissolved in <NUM> ethanol and <NUM> water, the pH value was <NUM>. This solution was cooled to <NUM> from <NUM> and <NUM> of a white precipitate of the sulfate salt of the compound of formula I was formed with <NUM>% HPLC purity in <NUM>% yield. XRPD analysis indicated that the sulfate salt of the compound of formula I was obtained as crystalline Form II (epimer ratio not determined).

<NUM> of the crude sulfate salt of the compound of formula I, HPLC purity <NUM>%, was dissolved in <NUM> ethanol and <NUM> water and the pH value was adjusted to <NUM> with concentrated sulfuric acid. The solution was cooled to -<NUM> from <NUM> over <NUM> hours and a precipitate of the sulfate salt of the compound of formula I was formed. The precipitate was filtered and dried to give <NUM> crystalline Form II with <NUM>% HPLC purity in <NUM>% yield (epimer ratio not determined).

<NUM> of the crude sulfate salt of the compound of formula I, HPLC purity <NUM>%, was dissolved in <NUM> ethanol and <NUM> water, the pH value was <NUM>. This solution was then cooled to -<NUM> from <NUM> over <NUM> hours and a precipitate of the sulfate salt of the compound of formula I was formed. The precipitate was filtered and dried to give <NUM> crystalline Form II in <NUM>% yield (epimer ratio not determined).

<NUM> of the crude sulfate salt of the compound of formula I, HPLC purity <NUM>%, was dissolved in <NUM> ethanol and <NUM> water, the pH value was <NUM>. <NUM> of crystalline Form I was added as seed. The mixture was then stirred over <NUM> hours at <NUM>-<NUM>, cooled to <NUM> over <NUM> hours and was allowed to stand for over <NUM> days at a <NUM>-<NUM>. During this time a precipitate formed giving <NUM>% yield and an epimer A to epimer B ratio of <NUM>:<NUM>. <NUM> of isopropanol was then added over <NUM> hours, and <NUM> of n-heptane was charged over <NUM> hours. After filtration and drying, <NUM> of the sulfate salt of the compound of formula I as crystalline Form I with <NUM>% purity was obtained, giving a total <NUM>% yield and an epimer A to epimer B ratio of <NUM>:<NUM>.

<NUM> of the crude sulfate salt of the compound of formula I, HPLC purity <NUM>% was dissolved in <NUM> ethanol and <NUM> water, the pH value was <NUM>. <NUM> of crystalline Form I was added as seed. The mixture was then stirred over <NUM> hours at <NUM>-<NUM>, cooled to <NUM> over <NUM> hours and was allowed to stand for over <NUM> days at <NUM>. After filtration and drying, <NUM> of the sulfate salt of the compound of formula I as crystalline Form I with <NUM>% purity was obtained in <NUM>% yield with an epimer A to epimer B ratio of <NUM>:<NUM>.

<NUM> of crude sulfate salt of the compound of formula I (BAL0008557-<NUM>), HPLC purity <NUM>% was dissolved in <NUM> cyclohexanol and <NUM> water, the pH value was adjusted to <NUM>. <NUM> of crystalline form I was added as seed. The mixture was then stirred over <NUM> hours at <NUM>-<NUM>, cooled to <NUM>-<NUM> over <NUM> hours and was allowed to stand for over <NUM> days at <NUM>. <NUM> of isopropanol was then added over <NUM> hours, and <NUM> of n-heptane was charged over <NUM> hours. After filtration and drying, <NUM> of the sulfate salt of the compound of formula I as crystalline Form I with <NUM>% purity was obtained, giving a total <NUM> % yield and an epimer A to epimer B ratio of <NUM>.

<NUM> of crude sulfate salt of the compound of formula I (BAL0008557-<NUM>), HPLC purity <NUM>% was dissolved in <NUM> n-butanol and <NUM> water, the pH value was adjusted to <NUM>. <NUM> of crystalline form I was added as seed. The mixture was then stirred over <NUM> hours at <NUM>-<NUM>, cooled to <NUM>-<NUM> over <NUM> hours and was allowed to stand for over <NUM> days at <NUM>. <NUM> of isopropanol was then added over <NUM> hours, and <NUM> of n-heptane was charged over <NUM> hours. After filtration and drying, <NUM> of the sulfate salt of the compound of formula I as crystalline Form I with <NUM>% purity was obtained, giving a total <NUM> % yield and an epimer A to epimer B ratio of <NUM>.

<NUM> of crude sulfate salt of the compound of formula I (BAL0008557-<NUM>), HPLC purity <NUM>% was dissolved in <NUM> anhydrous ethanol. The pH value was adjusted to <NUM>. <NUM> of crystalline form I was added as seed. The mixture was then stirred over <NUM> hours at <NUM>-<NUM>, cooled to <NUM>-<NUM> over <NUM> hours and was allowed to stand for over <NUM> days at <NUM>. <NUM> of isopropanol was then added over <NUM> hours, and <NUM> of n-heptane was charged over <NUM> hours. After filtration and drying, <NUM> of the sulfate salt of the compound of formula I as crystalline Form I with <NUM>% purity was obtained, giving a total <NUM> % yield and an epimer A to epimer B ratio of <NUM>.

<NUM> of crude sulfate salt of the compound of formula I (BAL0008557-<NUM>), HPLC purity <NUM>% was dissolved in <NUM> ethanol and <NUM> water, the pH value was adjusted to <NUM>. <NUM> of crystalline form I was added as seed. The mixture was then stirred over <NUM> hours at <NUM>-<NUM>, cooled to <NUM>-<NUM> over <NUM> hours and was allowed to stand for over <NUM> days at <NUM>. <NUM> of n-Heptane was then added over <NUM> hours. The mixture was then stirred over <NUM> hours at <NUM>-<NUM>. After filtration and drying, <NUM> of the sulfate salt of the compound of formula I with <NUM> % purity was obtained, giving a total <NUM> % yield and an epimer A to epimer B ratio of <NUM>.

<NUM> of crude sulfate salt of the compound of formula I (BAL0008557-<NUM>), HPLC purity <NUM>% was dissolved in <NUM> ethanol and <NUM> water, the pH value was adjusted to <NUM>. <NUM> of crystalline form I was added as seed. The mixture was then stirred over <NUM> hours at <NUM>-<NUM>, cooled to <NUM>-<NUM> over <NUM> hours and was allowed to stand for over <NUM> days at <NUM>. <NUM> of n-Hexane was then added over <NUM> hours. The mixture was then stirred over <NUM> hours at <NUM>-<NUM>. After filtration and drying, <NUM> of the sulfate salt of the compound of formula I with <NUM> % purity was obtained, giving a total <NUM> % yield and an epimer A to epimer B ratio of <NUM>.

<NUM> of crude sulfate salt of the compound of formula I (BAL0008557-<NUM>), HPLC purity <NUM>% was dissolved in <NUM> ethanol and <NUM> water, the pH value was adjusted to <NUM>. <NUM> of crystalline form I was added as seed. The mixture was then stirred over <NUM> hours at <NUM>-<NUM>, cooled to <NUM>-<NUM> over <NUM> hours and was allowed to stand for over <NUM> days at <NUM>. <NUM> of <NUM>-Hexene was then added over <NUM> hours. The mixture was then stirred over <NUM> hours at <NUM>-<NUM>. After filtration and drying, <NUM> of the sulfate salt of the compound of formula I with <NUM> % purity was obtained, giving a total <NUM> % yield and an epimer A to epimer B ratio of <NUM>.

<NUM> of crude sulfate salt of the compound of formula I (BAL0008557-<NUM>), HPLC purity <NUM>% was dissolved in <NUM> ethanol and <NUM> water, the pH value was adjusted to <NUM>. <NUM> of crystalline form I was added as seed. The mixture was then stirred over <NUM> hours at <NUM>-<NUM>, cooled to <NUM>-<NUM> over <NUM> hours and was allowed to stand for over <NUM> days at <NUM>. <NUM> of isopropanol was then added over <NUM> hours, <NUM> of n-heptane was then added over <NUM> hours. The mixture was then stirred over <NUM> hours at <NUM>-<NUM>. After filtration and drying, <NUM> of the sulfate salt of the compound of formula I with <NUM> % purity was obtained, giving a total <NUM> % yield and an epimer A to epimer B ratio of <NUM>.

<NUM> of crude sulfate salt of the compound of formula I (BAL0008557-<NUM>), HPLC purity <NUM>% was dissolved in <NUM> ethanol and <NUM> water, the pH value was adjusted to <NUM>. <NUM> of crystalline form I was added as seed. The mixture was then stirred over <NUM> hours at <NUM>-<NUM>, cooled to <NUM>-<NUM> over <NUM> hours and was allowed to stand for over <NUM> days at <NUM>. <NUM> of n-heptane was then added over <NUM> hours. The mixture was then stirred over <NUM> hours at <NUM>-<NUM>. After filtration and drying, <NUM> of the sulfate salt of the compound of formula I with <NUM> % purity was obtained, giving a total <NUM> % yield and an epimer A to epimer B ratio of <NUM>.

<NUM> of the crude sulfate salt of the compound of formula I (<NUM>% area HPLC purity) was dissolved in a mixture of <NUM> ethanol and <NUM> water, the pH value was <NUM>. The solution was cooled to -<NUM> and left to stand in a refrigerator for <NUM> days for recrystallization. After filtration and drying, <NUM> of the sulfate salt of the compound of formula I as crystalline Form I with <NUM>%area HPLC purity was obtained in <NUM>% yield (Epimer ratio not determined).

The HPLC column used was a Shiseido Chiral CD-Ph <NUM> column with dimensions <NUM> x <NUM>. The HPLC detector wavelength was <NUM> and the column was maintained at a temperature of <NUM> ° C ± <NUM>° C. The HPLC samples were prepared by dissolving <NUM> of product in <NUM> of dissolution mixture containing water, acetonitrile and trifluoroacetic acid in proportions <NUM>:<NUM>:<NUM>, which was shaken to homogenize the mixture. The HPLC mobile phase was a mixture of triethylammonium acetate and acetonitrile in proportions <NUM>:<NUM>, pH <NUM>. The mixture was shaken to homogenize and degassed. The injection volume was <NUM>µL and the flow rate was <NUM>/minute.

The retention times of the epimers were as follows:.

Example <NUM>: Characterisation of Form I and Form II of the sulfate salt of the compound of formula I XRPD patterns were obtained using a high-throughput XRPD set-up. The plates were mounted on a Bruker GADDS diffractometer equipped with a Hi-Star area detector. The XRPD platform was calibrated using Silver Behenate for the long d-spacings and Corundum for the short d-spacings. Data collection was carried out at room temperature using monochromatic CuKα radiation in the 2θ region between <NUM>° and <NUM>°, which is the most distinctive part of the XRPD pattern. The diffraction pattern of each well was collected in two <NUM> ranges (<NUM>°≤ 2θ ≤ <NUM>° for the first frame, and <NUM>°≤ 2θ ≤ <NUM>° for the second) with an exposure time of <NUM> seconds for each frame. No background subtraction or curve smoothing was applied to the XRPD patterns. The carrier material used during XRPD analysis was transparent to X-rays and contributed only slightly to the background.

The XRPD of Form I at room temperature is shown in <FIG> and its diffractogram peaks are shown in Table <NUM>. The XRPD of Form II at room temperature is shown in <FIG> and its diffractogram peaks are shown in Table <NUM>.

<NUM> of the crude sulfate salt of the compound of formula I was dissolved in <NUM> water and the solution was treated with saturated sodium bicarbonate at <NUM> to adjust the pH to <NUM>. Then the solution was extracted with <NUM> methylene chloride and the organic phase was concentrated to dryness. The crude product was dissolved in <NUM> of methanol at -<NUM> and then the solution was treated with <NUM> sulfuric acid and <NUM> <NUM>% aqueous hydrogen peroxide for <NUM>, after concentration to dryness. The product decomposed dramatically and no crystalline solid formed.

In a <NUM> flask, <NUM> of acetone, <NUM> of pure water and <NUM> of <NUM>-Methoxyethanol were added. <NUM> of the crude sulfate salt of the compound of formula I with HPLC purity <NUM>% with an epimer A to epimer B ratio of <NUM>:<NUM> was added. The solution was stirred at <NUM>-<NUM> for <NUM> hour, then <NUM> of ethyl acetate was added dropwise and the solution was stirred for <NUM> hours at <NUM>-<NUM>. The mixture was filtered under nitrogen and the cake was dried for <NUM> minutes to give <NUM> of the sulfate salt of the compound of formula I as crystalline Form I with <NUM>% HPLC purity and with <NUM>% yield.

Claim 1:
A method for purifying the sulfate salt of the compound of formula I
<CHM>
comprising the steps of
(a) providing a mixture comprising the sulfate salt of the compound of formula I and an aliphatic alcohol, wherein the aliphatic alcohol contains one or two OH groups, providing that when there are two OH groups there are three to six carbon atoms in the aliphatic moiety, and wherein the aliphatic moiety is a non-aromatic hydrocarbon moiety in which the constituent carbon atoms can be straight-chain, branched chain or cyclic, and wherein the pH of the mixture is in the range of about pH <NUM> to about pH <NUM>, wherein the term "about" indicates a variation of +/- <NUM>% of the given value;
(b) allowing a first portion of the sulfate salt of the compound of formula I to crystalize from the mixture; and
(c) adding an aprotic organic solvent to the mixture and allowing an additional portion of the sulfate salt of the compound of formula I to precipitate from the mixture.