Process for the production of (3s,6r)-6-(cyanomethyl)-tetrahydro-2h-pyran-3-amine

Abstract

The present disclosure relates to a process for the synthesis of ((3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-yl) hydrochloride, a key pharmaceutical intermediate. The process achieves approximately twice the percentage yield of the known process with greener chemistry and advantageously eliminates a resource-intensive step to improve industrial efficiency and applicability.

Description

[0001] Cross-reference to related applications

[0002] This international application claims priority to U.S. Provisional Patent Application No. 63 / 518,854, filed August 10, 2023, which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure relates to the discovery of a dynamic method for synthesizing ((3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine) hydrochloride in high yield, i.e., a key pharmaceutical intermediate. Background Technology

[0004] The compound (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine hydrochloride (referred to as APA) is a chiral intermediate that can be used to prepare pharmaceutical compounds such as the TYK2 / JAK1 inhibitor BHV-8000 (formerly known as TLL-041). However, existing methods for producing this chiral intermediate, or other useful salts of the compound (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine, are inefficient and yield low amounts. Therefore, improved methods for producing this intermediate are necessary.

[0005] It has been found that low yields are due to an unsuitable ratio of desired to undesired diastereomers generated during the ring-closing reaction step. This disclosure provides a dynamic synthetic method that achieves favorable diastereomer ratios and provides significantly improved yields on an industrially relevant scale. This dynamic method involves converting the undesired diastereomer back to the starting material as the reaction proceeds to accumulate an excess of the desired diastereomer. The described method also displaces harmful and expensive solvents, which is advantageous from a green chemistry perspective. Furthermore, resource-intensive steps can be avoided to more efficiently generate the critical APA intermediate. Summary of the Invention

[0006] Therefore, this disclosure relates to an improved method for synthesizing ((3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine) hydrochloride or other useful salts of ((3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine). The following embodiments are illustrative and cover other embodiments described herein.

[0007] In one implementation, a method is provided that includes:

[0008] (2S)-6-cyano-5-hexen-1-ol-2-amine having a protecting group on an amine is reacted with a base in an alcoholic solvent to produce (via a ring-closing reaction) a reaction mixture containing a diastereomeric mixture of (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine and (3S,6S)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine.

[0009] In one embodiment, the pKa of the conjugate acid of the base is about 16 to about 20.

[0010] In one implementation, the base is a salt of an alkoxide ion.

[0011] In one embodiment, the alkoxide ion is a tert-butoxide ion or an isopropoxide ion.

[0012] In one embodiment, the salt is potassium tert-butoxide, sodium tert-butoxide, or lithium tert-butoxide.

[0013] In one embodiment, the salt is potassium tert-butoxide.

[0014] In one embodiment, the alcohol solvent includes one or more of the following: methanol, ethanol, n-propanol, isopropanol, butanol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, isoamyl alcohol, and tert-amyl alcohol.

[0015] In one embodiment, the alcohol solvent includes isopropanol. In another embodiment, the alcohol solvent is isopropanol.

[0016] In one embodiment, the protecting group on the amine is selected from the group consisting of: benzyl carbamate (Cbz), acetamide (Ac), trifluoroacetamide (TFAc), phthalimide, triphenylmethylamine (Tr), benzylamine and p-toluenesulfonamide (Ts) and tert-butyloxycarbonyl.

[0017] In one embodiment, the protecting group on the amine is a tert-butyloxycarbonyl group.

[0018] In one embodiment, the ring-closing reaction occurs in the range of about 10°C to 50°C. 0 At a temperature of C, choose any temperature between 20℃ and 30℃. 0 Perform under C.

[0019] In one embodiment, the ring-closing reaction is carried out for about 24 hours, or until the amount of (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having the protecting group on the amine no longer increases.

[0020] In one embodiment, the method further includes quenching the reaction mixture with an acidic solution to neutralize the base after the ring-closing reaction is complete.

[0021] In one embodiment, a solid phase comprising (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine and (3S,6S)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine is precipitated from an alcohol solvent.

[0022] In one embodiment, the solid phase comprises a diastereomeric ratio of (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine to that of (3S,6S)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine, which is at least about 75:25. In one embodiment, the diastereomeric ratio is about 90:10.

[0023] In one embodiment, the method further includes filtering the solid phase from the reaction mixture.

[0024] In one embodiment, the method further includes purifying (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine from a solid phase.

[0025] In one embodiment, (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine is purified from the diastereomeric mixture at a diastereomeric ratio of about 99:1.

[0026] In one embodiment, the purification includes contacting the diastereomeric mixture with a purification solvent in which (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine is insoluble and precipitates from the solution, while (3S,6S)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine is soluble and remains in the solution; and filtering the resulting purified precipitate containing (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine.

[0027] In one embodiment, the purification solvent comprises methyl tert-butyl ether. In another embodiment, the purification solvent is methyl tert-butyl ether.

[0028] In one embodiment, the method further includes reacting the purified (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine with hydrochloric acid to deprotect the amine and form ((3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-yl) hydrochloride.

[0029] In one embodiment, the method further includes separating ((3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-yl) hydrochloride.

[0030] In another embodiment, a method is provided that includes:

[0031] (2S)-6-cyano-5-hexen-1-ol-2-amine, having a protecting group on its amine, is reacted with a base in a solvent to produce a reaction mixture containing a solid phase, wherein:

[0032] The solid phase comprises a diastereomeric mixture of (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine and (3S,6S)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine;

[0033] The (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine is insoluble in the solvent; and

[0034] The (3S,6S)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine is at least partially soluble in the solvent.

[0035] In one embodiment, the solvent may be miscible with water.

[0036] In one embodiment, the solvent is a weak acid.

[0037] In one embodiment, the pKa of the solvent differs from the pKa of the conjugate acid of the base by about 25% or less.

[0038] In one embodiment, the solvent has a pKa of about 16 to about 20.

[0039] In one embodiment, the solid phase contains a diastereomeric ratio of (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine to that of (3S,6S)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine, which is at least about 75:25, preferably about 90:10.

[0040] In another embodiment, a method is provided that includes:

[0041] (2S)-6-cyano-5-hexen-1-ol-2-amine, having a protecting group on its amine, is reacted with an alkoxide base in an alcoholic solvent to produce a reaction mixture containing a solid phase, wherein:

[0042] The solid phase comprises a diastereomeric mixture of (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine and (3S,6S)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine; and

[0043] The ratio of the diastereomeric form of the solid phase having a protecting group on the amine (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine to the diastereomeric form of the amine having a protecting group on the amine is at least about 75:25.

[0044] In one implementation, the reaction is carried out until at least about 80% of the APA-7 is converted to APA-8.

[0045] In one embodiment, the reaction is carried out at approximately 10°C-50°C. 0 At a temperature of C, choose any temperature between 20℃ and 30℃. 0 Perform under C.

[0046] In one embodiment, the reaction mixture is stirred or agitated while the closed-loop reaction is being carried out. Attached Figure Description

[0047] The aspects and advantages of this disclosure will become apparent from the following exemplary embodiments, taken in conjunction with the accompanying drawings, wherein:

[0048] Figure 1 A reference method for producing APA-8 is described;

[0049] Figure 2 An exemplary method for producing APA-8 is described;

[0050] Figure 3 The crystallization-induced dynamic resolution of the desired APA-8 product, which can accumulate diastereomer excesses, is described.

[0051] Figure 4 The HPLC chromatograms of the produced and purified APA-8 are described;

[0052] Figure 5 LC-MS data describing the production and purification of APA-8;

[0053] Figure 6 The production and purification of APA-8 are described. 1 H NMR spectrum;

[0054] Figure 7 The production and purification of APA-8 are described. 13 C NMR spectrum; and

[0055] Figure 8 The IR spectra of the produced and purified APA-8 are described. Detailed Implementation

[0056] The compound ((3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine) hydrochloride (APA) is a key intermediate used in the synthesis of pharmaceutical compounds such as BHV-8000. The structure of APA in hydrochloride form is shown below.

[0057]

[0058] APA can be synthesized from readily available L-glutamic acid starting material according to the synthetic scheme shown in Scheme 1 below. Additional synthetic schemes for the production of APA-7 are also covered.

[0059]

[0060] Option 1: Synthesis of chiral intermediate APA

[0061] At step 8 of the method, APA-7 (a linear olefin ((2S)-6-cyano-5-hexen-1-ol-2-amine)) undergoes ring-closing conditions to produce APA-8, which can be deprotected to form APA. APA-8 (i.e., ((3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-yl)carbamate tert-butyl ester) as shown above is the desired trans diastereomeric form of the chiral intermediate APA. The ring-closing reaction of APA-7 also tends to produce an undesirable cis diastereomeric form, referred to as APA-8b (i.e., ((3S,6S)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-yl)carbamate tert-butyl ester). While “APA-8” and “APA-8b” refer to specific structures containing the Boc protecting group, it should be understood that the description of these terms can cover the same compounds having other suitable protecting groups as described herein. APA-8 and APA-8b are shown below.

[0062]

[0063] This disclosure provides an improved synthetic procedure for producing the desired diastereomeric APA-8, along with other related improvements. Known methods for producing APA-8, compared to APA-8b (the undesired stereoisomer), result in lower yields of the desired stereoisomer and are unfavorable to stereoisomerism. Related prior methods are generally described in International Application No. PCT / CN2022 / 129966, filed December 19, 2022 (corresponding to WO 2023 / 125102 published July 6, 2023), filed by Congxin et al., which is incorporated herein by reference. An example based on this prior method is shown below.

[0064]

[0065] Option 2: An exemplary reference method for producing APA-8 from APA-7.

[0066] APA-8 corresponds to compound 2-2 of Congxin et al., and that reference reports a yield of 42.2% and a scale of 43.2 kg for the isolated compound. Congxin et al. did not discuss the ratio of diastereomers produced by this reaction. However, the diastereomers described in scheme 2 generally produce ring-closing reactions. To obtain APA-8 from a mixture of diastereomer products of APA-8 and APA-8b, aqueous posttreatment, organic extraction, carbon (charcoal) treatment, and distillation steps were employed. As discussed herein, a version of the method of Congxin et al. was carried out in a comparable yield, partly due to poor selectivity for the diastereomers of APA-8.

[0067] Figure 1 A flowchart of the modified method of Congxin et al. (hereinafter referred to as the “Reference Method”) performed as a comparison with the dynamic method described herein is described. Following the Reference Method, APA-7 was reacted with sodium methoxide (NaOMe) in a tetrahydrofuran (THF) solvent. Based on the reaction mixture (RM), the ratio of diastereomeric APA-8 to APA-8b was determined to be 60:40, meaning that 40% of the resulting material was direct waste of the Reference Method. After post-treatment, extraction, and purification (carbon treatment, distillation, and recrystallization from MTBE), APA-8 was obtained with a separation yield of approximately 40% and a purity >98%, based on the amount of APA-7 utilized. Because the Reference Method was carried out in a THF solvent, post-treatment, extraction, carbon treatment, and distillation steps were required, as the solvent is insoluble in water and must be removed from the product. This is comparable to the 42.2% yield and 96% purity reported by Congxin et al.

[0068] On an industrial scale, the 60:40 diastereomeric ratio according to the reference method is unacceptable for efficiency and economic reasons. Furthermore, from a green chemistry perspective, it is advantageous to replace THF with more economical and environmentally friendly solvents and to avoid resource-intensive steps such as aqueous solution post-treatment, organic extraction, carbon treatment, and distillation.

[0069] Therefore, the present invention provides a solution to these problems by means of an alternative dynamic synthesis procedure that produces APA-8 from APA-7 on an industrial-scale basis, wherein the reaction mixture ratio of diastereomeric APA-8 to APA-8b is approximately 90:10, and the separation yield of APA-8 is approximately doubled to approximately 80% based on the amount of APA-7 used. The method described herein also avoids the use of THF, instead using greener solvents such as alcohols (e.g., isopropanol (IPA) or other alcohols). Furthermore, the resource-intensive aqueous post-treatment, organic extraction, carbon treatment, and distillation steps can be avoided according to this dynamic method, thereby producing the separated product in high yield. This dynamic method is described in Embodiment 3 below.

[0070]

[0071] Option 3: An exemplary dynamic method for producing APA-8 from APA-7.

[0072] Figure 2 An exemplary dynamic method according to this disclosure is described. This method reacts APA-7 with potassium tert-butoxide (KOtBu) in isopropanol (IPA) to produce APA-8 (90%) as a precipitated solid product with a favorable diastereomeric ratio compared to the byproduct APA-8b (10%). As a direct result of this improvement, the yield of APA-8 product separated according to the dynamic method (≈80%) is approximately twice that of the 40% yield of the reference method. As will be further described herein, the dynamic method demonstrates industrial applicability by producing such high yields on a kilogram scale.

[0073] It has been found that the favorable diastereomeric ratio and the resulting high yield are partly due to the use of a solvent in which APA-8 is insoluble, while APA-8b is a relatively soluble solvent. This phenomenon is as follows: Figure 3The process described herein, and referred to as crystallization-induced dynamic resolution, is described. The term crystallization as used herein does not necessarily imply any particular ordered structure or crystal structure, but rather refers to the precipitation of the desired material from the reaction mixture. Because APA-8b is more soluble in the reaction mixture, it will undergo a reverse ring-opening reaction to form a linear APA-7 product, which will then undergo a ring-closing reaction again. Therefore, statistically, APA-8 formed from each ring-closing reaction precipitates or crystallizes from the solvent, where it does not readily undergo the reverse reaction and forms a diastereomeric excess of APA-8 product over time. Given its similar properties to isopropanol, alcohol solvents having 1 to 5 carbon atoms (i.e., from methanol to pentanol with one or more hydroxyl groups) will have a favorable effect on the diastereomeric distribution compared to the reference method solvent THF. Additionally, this disclosure covers other protic organic solvents in which APA-8 has poorer solubility compared to APA-8b.

[0074] This dynamic method offers several additional improvements for obtaining APA-8 with high chiral purity, while eliminating several undesirable steps utilized in the reference method, including aqueous solution post-treatment, extraction, carbonization, and distillation. In one aspect, these steps are avoided by using water-miscible solvents instead of immiscible THF. On an industrial scale, eliminating these steps is significant.

[0075] In one embodiment, APA-7 is reacted with a strong base or a relatively strong base in a solvent to produce a favorable diastereomeric distribution of APA-8 and APA-8b. In one embodiment, the solvent is a protic organic solvent. In one embodiment, the solvent is a weak acid (meaning, herein, that it has a pKa of about 10 or higher, or that its conjugate base is capable of deprotonating APA-7 to initiate a cyclization reaction). In one embodiment, the solvent has a pKa ranging from about 16 to about 20. aIn one embodiment, the pKa of the solvent differs from that of the conjugate acid of the base by about 25% or less, including solvents having the same pKa as the conjugate acid of the base (e.g., isopropanol solvent and isopropanol base). In one embodiment, the solvent is an organic solvent containing an alcohol. In one embodiment, the solvent is an alcohol. In one embodiment, the alcohol contains 1 to 5 carbon atoms. In one embodiment, the alcohol is selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, butanol (including 1-butanol, 2-butanol, tert-butanol, and isobutanol), and various isomers of butanediol and pentanol (including isoamyl alcohol and tert-amyl alcohol). Other alcohol solvents may include ethylene glycol, propylene glycol, etc. In one embodiment, the alcohol is isopropanol. The amount of solvent in a particular reaction can be adjusted as needed; however, in some embodiments, approximately 6 mL of solvent per gram of APA-7 is used. In other embodiments, from approximately 1 mL of solvent per gram of APA-7 to approximately 100 mL of solvent per gram of APA-7 can be used.

[0076] As used herein, the term "APA-7" generally refers to the compound (2S)-6-cyano-5-hexen-1-ol-2-amine having a protecting group on an amine. While Boc (tert-butyl carbamate) is a suitable protecting group, other protecting groups may also be used. As a non-limiting list of protecting groups, benzyl carbamate (Cbz), acetamide (Ac), trifluoroacetamide (TFAc), phthalimide, triphenylmethylamine (Tr), benzyleneamine, and p-toluenesulfonamide (Ts) may be used in alternative embodiments. Similarly, the use of this terminology or similar terminology to refer to the compound (2S)-6-cyano-5-hexen-1-ol-2-amine having a protected amine is intended to cover any protected form of the compound. It should be understood that the protected amine involves bond substitution of one or more protected groups on the hydrogen atoms. Generally, when a compound (APA-7, APA-8, or APA-8b) is described as "protected," it should be understood that the protecting group is bonded to the amine group.

[0077] In one embodiment, a base with suitable alkalinity is used. In one embodiment, the base is a strong base or a relatively strong base (e.g., a base stronger than hydroxides but less strong than butyllithium and related bases). In one embodiment, the base strength can be determined by the acid dissociation constant (pK) of its conjugate acid. a The negative logarithm of ) is defined as follows, where the higher pK is... a The conjugate acid is indicated by a lower acidity, and therefore the base by a higher basicity. In one embodiment, the pK of the conjugate acid of the base is... aThe range is from about 16 to about 20. One example of a suitable base is an alkoxide, although other bases capable of catalyzing ring-closing reactions are also included. In one embodiment, the base is an alkoxide base. Alkoxide bases are typically introduced as a salt of an alkoxide ion. For example, ionic complexes comprising cations such as potassium, sodium, or lithium and alkoxide anions can be utilized. In various embodiments, the cation can be an alkali metal cation, such as potassium (K... + ), sodium (Na + ) or lithium (Li + In alternative embodiments, other cations may be present. For example, basic dications, such as Mg, may be utilized. 2+ or Ca 2+ Or a single cation, such as (MgCl) + Generally, this encompasses any ionic complex that includes a useful alkoxide base. The salt is typically soluble in the reaction mixture, meaning the ionic complex dissociates to provide a certain amount of accessible base.

[0078] The alkoxide can be straight-chain (such as methanol, ethanol, and n-propoxide) or branched (such as isopropoxide, tert-butoxide, and 2-butoxide). The amount of base used can vary depending on the reaction conditions and can alter the total reaction time. In some embodiments, the amount of strong base is about 0.1 molar equivalents of APA-7; however, the amount of strong base can vary. For example, in other embodiments, the amount of strong base can be about 0.01 molar equivalents of APA-7, 0.1 molar equivalents of APA-7, 1 molar equivalent of APA-7, or higher. Because the base is catalytic, it is typically present at a lower concentration compared to APA-7.

[0079] In one implementation, APA-8 is generated from APA-7 at an enantiomeric ratio of at least 70:30, or at least 75:25, or at least 80:20, or at least 85:15, or at least 90:10 (as defined by APA-8:APA-8b) (where “at least” encompasses an APA-8 ratio higher than the first number stated in the ratio, and an APA-8b ratio lower than the number stated in the ratio).

[0080] In one embodiment, APA-7 is reacted with a base in a solvent for a sufficient time to complete the conversion to APA-8 (and the minor product APA-8b) at a given reaction temperature. For example, the reaction can be carried out at 25°C ± 5°C. 0The reaction is carried out at C for approximately 24 hours. In an alternative embodiment, the reaction can be carried out at a lower temperature above the freezing point of the solvent, which makes the reaction kinetically feasible and does not render the undesirable APA-8b product insoluble. The reaction temperature should also not be high enough to dissolve the desired APA-8 product or prevent its precipitation. For example, in an alternative embodiment, the temperature can be approximately 10°C. 0 C to approximately 50 0 C. Those skilled in the art are typically able to monitor the reaction products to determine the appropriate temperature and time conditions for a given ring-closing reaction of APA-7.

[0081] Following the ring-closing reaction of APA-7, the heterogeneous reaction mixture (RM) contains the major product APA-8 as a precipitate or crystallization product, along with dissolved minor products APA-8b, residual APA-7, solvent, base, and trace byproducts. The precipitated APA-8 product may also contain small amounts of APA-8b and other trace impurities, which are removed in subsequent purification steps. The RM can then be quenched, for example, by adding sufficient water. An excess of water can be used, such as, for example, 20 mL of water per gram of APA-7. Preferably, the water may contain an acid in the same or similar molar equivalent to the base. For example, in one embodiment, the water used for quenching the reaction may contain ammonium chloride or another acid. The acid can first be added to a small aliquot of water (such as about 0.25 mL per gram of APA-7) and stirred for a few minutes (e.g., 10-15 minutes), followed by the addition of excess water. The RM can be cooled before, during, or after quenching to maintain or lower its temperature as a result of the exothermic quenching. For example, the RM can be cooled and maintained at about 0°C. 0 C to approximately 10 0 The temperature should be set at C, or maintained as needed to avoid product loss. The RM can be cooled for a period of time, such as about 1 hour, to ensure quenching is complete. Once quenched, the wet product containing APA-8 can be collected by gravity filtration, vacuum filtration, or other methods to remove the liquid phase. During filtration, the wet product can be washed with water.

[0082] The wet product obtained from filtration can then be purified. In an alternative embodiment, the wet product can first be dried and then rewetted with water, although purification of the wet product obtained from the reaction is generally more efficient. Various purification methods are covered, including but not limited to chemical purification, chromatographic purification (column or high-throughput), and any other methods. Non-limiting examples of chemical purification are described below.

[0083] In one embodiment, the product is purified by recrystallization from methyl tert-butyl ether (MTBE). In one embodiment, the wet material (containing APA-8) is mixed with about 3 mL of methyl tert-butyl ether (MTBE) per gram of APA-7 used. As will be understood by those skilled in the art, more or less MTBE can be used. The MTBE suspension can be heated at about 25°C–30°C. 0 Stir at C for at least about 1 hour, which dissolves at least some of the wet material containing APA-8. Then, cool the mixture to about 0°C-5°C. 0 C (where APA-8 forms solid crystals), and then mix for at least about 1 hour. The liquid can then be removed by vacuum filtration, and the solid can be washed with cooled MTBE. The obtained solid can then be dried to obtain the purified APA-8 product. Although MTBE is generally preferred, any solvent in which APA-8 is relatively insoluble can be used for the purification and crystallization of the APA-8 product compared to APA-8b.

[0084] As an optional or additional step, before or after MTBE washing, the wet material can be mixed with approximately 5 mL of n-heptane per gram of APA-7 used. The n-heptane suspension can be incubated at 25°C–30°C. 0 Stir at C for at least about 30 minutes, then filter under vacuum and wash with n-heptane. Washing with n-heptane helps remove additional solvents or other impurities from the wet material before recrystallization. Other volatile solvents, such as hexane, can be used.

[0085] While the described methods advantageously avoid aqueous post-treatment, organic extraction, carbon treatment, and distillation, these or other methods can be used in a variety of alternative embodiments. Those skilled in the art will understand other alternative embodiments of the methods, and such alternative embodiments are covered herein.

[0086] Example

[0087] Example 1: Synthesis of ((3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-yl)carbamate tert-butyl ester (APA-8):

[0088]

[0089] Option 4: An exemplary method for producing APA-8

[0090] At 0-5°C, potassium tert-butoxide (2.33 g, 20.8 mmol) was added to a stirred solution of (S)-(6-cyano-1-hydroxyhex-5-en-2-yl)carbamate, i.e., APA7 (50.0 g, 208 mmol), in isopropanol (300 mL). The reaction mixture was brought to 25-30°C and stirred at the same temperature (25-30°C) for 36 h (observation: the reaction mass became heterogeneous during the holding period). After the reaction was complete (chemical conversion and desired / undesired isomer ratio monitored by HPLC), the reaction mixture was quenched with 20% ammonium chloride solution (25 mL) below 30°C, and the mixture was stirred at 25-30°C for 30 min. Water (1000 mL) was added to the mixture over a 20-minute period at 25-30°C, and the mixture was stirred for 30 min. Cool the material to 0℃-10℃ and stir for 1 h. Filter the resulting solid, wash with water (250 mL), and vacuum dry for 30 min. Collect the wet material and subject it to the following purification method.

[0091] Purification of the wet material: MTBE (150 mL) and APA8 wet material were placed in a round-bottom flask and stirred at 25℃-30℃ for 1 h. The material was cooled to 0℃-5℃ and stirred at 0℃-5℃ for 1 h. The solid was filtered and washed with MTBE (100 mL), and dried under vacuum for 30 min. The solid was dried under vacuum at below 45℃ for 8 h. APA8 weight: 43.0 g, yield: 86%.

[0092] In summary, APA-8 was successfully obtained through a process involving reaction, quenching, purification, and drying. Various analytical techniques were employed, including HPLC, LC-MS, and... 1 H NMR, 13 The obtained products were characterized by C NMR and FT-IR.

[0093] HPLC was performed using a Dura Shell C18 (250 x 4.6) mm x 5.0 µm column or equivalent (lot number: 110805) and UV / PDA detection. The chromatographic conditions are shown in Table 1 below.

[0094] Table 1: HPLC Chromatographic Conditions

[0095]

[0096] Under these conditions, APA-7, APA-8, and APA-8b (listed in elution order) were found to have different distinguishable retention times. Figure 4As shown in the exemplary chromatograms, these retention times correspond to 19.9, 24.7, and 25.7 minutes, respectively.

[0097] The APA-8 product resolved by HPLC was subjected to mass spectrometry (MS). The instrument conditions for MS are shown in Table 2 below, and exemplary LC-MS data are as follows: Figure 5 As shown in the image.

[0098] Table 2: LC-MS Conditions

[0099]

[0100] NMR spectroscopy ( 1 H and 13 C) was used to characterize and verify the obtained APA-8 structure. One-dimensional NMR spectra were obtained on a 300 MHz Bruker NMR spectrometer. This was achieved by using a large number of (for) 1 The H NMR value is 5 mg, for 13 A 20 mg APA-8 sample was dissolved in 0.7 mL of DMSO-d6 solvent, and then the solution was transferred to an NMR tube to prepare the sample. (Exemplary example) 1 H and 13 The CNMR spectra are shown in Figure 6 and Figure 7 middle.

[0101] Fourier transform infrared (FTIR) spectra were collected using potassium bromide (KBr) particles on a Shimadzu spectrometer. Approximately 3 to 4 mg of sample was mixed with approximately 300 to 400 mg of KBr in an agate mortar. The mixed powder was granulated using a hydraulic press. Measurements were taken at 4000 to 400 cm⁻¹. -1 The scanning was performed within the specified range, with a resolution of 4 cm. -1 . Figure 8 An example IR spectrum is shown below.

[0102] Summary of analysis data

[0103] HPLC chemical purity: 98.96%.

[0104] The ratio of desired to undesired isomers in the purified product was 99.31:0.68.

[0105] IR (KBr): 3361, 2978, 2868, 2252, 1681, 1525, 1313, 1244, 1180, 1089,1060, 873, 607 cm -1 .

[0106] 1 H-NMR (300 MHz, DMSO-d6): δ 6.804-6.778 (1H, d, J = 7.8 Hz,), 3.821-3.777 (1H, dd, J = 10.5, 2.4 Hz), 3.461-3.419 (1H, m), 3.350-3.324 (1H, m),3.021-2.950 (1H, t, J = 10.5 Hz), 2.787-2.600 (2H, m), 1.880-1.810 (1H, m),1.721-1.682 (1H, m), 1.391-1.307 (2H, m), 1.350 (9H, s) ppm.

[0107] 13 C-NMR (75 MHz, DMSO-d6): δ 154.97, 118.39, 77.79, 71.99, 70.29, 45.83, 29.67, 28.76, 28.18, 23.34 ppm.

[0108] Mass (ES+): m / z = 241.2234 (M++1); Melting range: 166.3℃ to 169.5℃

[0109] Example 2: Reference Method

[0110] In comparison, based on Figure 1The method described herein is a reference method. (S)-(6-cyano-1-hydroxyhex-5-en-2-yl)carbamate tert-butyl, i.e., APA7 (34.0 g, 141.4 mmol), was stirred in a THF (340 mL) stirring solution for 10 min. The reaction was cooled to 0-5°C, and methanol (7.64 g, 35.37 mmol) containing 25% sodium methoxide was added. The reaction mixture was stirred at 0-5°C for 1.0 h. The reaction mixture was quenched with ammonium chloride solution (85 mL), and the layers and aqueous layer were separated. The layers were extracted with MTBE (170 mL), and the two organic layers were combined and washed with a brine solution (100 mL). Charcoal (3.4 g) was added to the organic layer at 25-30°C, and the temperature was raised to 45-50°C and maintained for 30 min. The layer was filtered through a diatomaceous earth bed and washed with MTBE (17 mL). The filtrate was distilled under vacuum at 40°C, MTBE (100 mL) was added, and the mixture was heated to 50°C-55°C and stirred for 1.0 h. The mixture was then brought to 20°C-30°C and maintained for 1.0 h. The mixture was cooled to 0°C-10°C and maintained for 1.0 h. The solid was filtered and washed with pre-cooled MTBE (34 mL). The solid was dried under vacuum at below 45°C for 8 h. APA8 weight: 12.9 g, yield: 38%. HPLC chemical purity: 99.09%; desired to undesired isomer ratio: 99.09:0.91.

[0111] Example 3: Repeated Batch and Scale-up

[0112] According to the dynamic method, repeated batches of APA-8 were conducted at scales ranging from 50 g to 62 kg to test reproducibility under different reaction conditions and to scale up to an industrial-related scale. As seen in Table 3 below, excellent diastereomeric ratios were obtained for the desired isomer (isomer 1 in the table, where isomer 2 is the undesired APA-8b product), with higher yields based on the amount of starting material (APA-7), and higher purity of the purified products for the dynamic method (Examples 2–6). Example 1 is shown as a comparison according to the reference method.

[0113] Table 3: Repeat and Scale-up Batches

[0114]

[0115] Inclusion of references

[0116] The full disclosure of each patent document, including amendment certificates, patent application documents, scientific articles, government reports, websites, and other references mentioned herein, is incorporated herein by reference in its entirety for all purposes. In the event of conflicting terminology, this specification shall prevail.

[0117] equivalent

[0118] The invention may be practiced in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are to be considered illustrative in all respects and not to limit the scope of the invention described herein. In various embodiments of the compositions and methods of the invention, when the terminology is used with respect to the described components of the composition or the steps of the method, it also covers compositions and methods that are substantially composed of, or consist of, the described steps or components. Furthermore, it should be understood that the order of the steps or the order in which certain actions are performed is not important, as long as the invention remains operable. Moreover, two or more steps or actions may be performed simultaneously.

[0119] In this specification, unless the context clearly specifies otherwise, the singular form also includes the plural form. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of conflict, this specification shall prevail.

[0120] Furthermore, it should be recognized that in some cases, a composition can be described as consisting of components before mixing, because during mixing, some components may further react or be transformed into other materials.

[0121] Unless otherwise indicated, all percentages and ratios used herein are by weight.

Claims

1. A method comprising: (2S)-6-cyano-5-hexen-1-ol-2-amine having a protecting group on the amine is reacted with a base in an alcohol solvent to produce a reaction mixture containing a diastereomeric mixture of (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine and (3S,6S)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine.

2. The method of claim 1, wherein the pKa of the conjugate acid of the base is about 16 to about 20.

3. The method of claim 1, wherein the base is a salt of an alkoxide ion.

4. The method of claim 3, wherein the alkoxide ion is a tert-butoxide ion or an isopropoxide ion.

5. The method of claim 3, wherein the salt is potassium tert-butoxide, sodium tert-butoxide, or lithium tert-butoxide.

6. The method of claim 5, wherein the salt is potassium tert-butoxide.

7. The method of claim 1, wherein the alcohol solvent comprises one or more of the following: methanol, ethanol, n-propanol, isopropanol, butanol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, isoamyl alcohol, and tert-amyl alcohol.

8. The method of claim 7, wherein the alcohol solvent comprises isopropanol.

9. The method of claim 1, wherein the alcohol solvent is isopropanol.

10. The method of claim 1, wherein the protecting group on the amine is selected from the group consisting of: benzyl carbamate (Cbz), acetamide (Ac), trifluoroacetamide (TFAc), phthalimide, triphenylmethylamine (Tr), benzylamine and p-toluenesulfonamide (Ts) and tert-butyloxycarbonyl.

11. The method of claim 10, wherein the protecting group on the amine is tert-butoxycarbonyl.

12. The method of claim 1, wherein the temperature ranges from about 10°C to 50°C. 0 At a temperature of C, choose any temperature between 20℃ and 30℃. 0 Perform under C.

13. The method of claim 12, wherein it is carried out for about 24 hours, or until the amount of (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine no longer increases.

14. The method of claim 1, further comprising quenching the reaction mixture with an acidic solution to neutralize the base.

15. The method of claim 1, wherein a solid phase of (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine and (3S,6S)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine is precipitated from the alcohol solvent.

16. The method of claim 15, wherein the ratio of the diastereomeric form of (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine to that of (3S,6S)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine in the solid phase is at least about 75:

25.

17. The method of claim 16, wherein the diastereomeric ratio is about 90:

10.

18. The method of any one of claims 15 to 17, further comprising filtering the solid phase from the reaction mixture.

19. The method of any one of claims 1 to 18, further comprising purifying (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine from the solid phase.

20. The method of claim 19, wherein (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine is purified from the diastereomeric mixture at a diastereomeric ratio of about 99:

1.

21. The method of claim 19 or claim 20, wherein the purification comprises contacting the diastereomeric mixture with a purification solvent in which (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine is insoluble and precipitates from the solution, while (3S,6S)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine is soluble and remains in the solution; and filtering the resulting purified precipitate, the precipitate containing (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine.

22. The method of claim 21, wherein the purification solvent comprises methyl tert-butyl ether.

23. The method of claim 21, wherein the purification solvent is methyl tert-butyl ether.

24. The method of any one of claims 19 to 23, further comprising reacting the purified (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine with hydrochloric acid to deprotect the amine and form ((3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-yl) hydrochloride.

25. The method of claim 24, further comprising separating the ((3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-yl) hydrochloride.

26. A method comprising: (2S)-6-cyano-5-hexen-1-ol-2-amine, having a protecting group on its amine, is reacted with a base in a solvent to produce a reaction mixture containing a solid phase, wherein: The solid phase comprises a diastereomeric mixture of (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine and (3S,6S)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine; The (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine is insoluble in the solvent; and The (3S,6S)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine is at least partially soluble in the solvent.

27. The method of claim 26, wherein the solvent is miscible with water.

28. The method of claim 27, wherein the solvent is a weak acid.

29. The method of claim 26, wherein the pKa of the solvent differs from the pKa of the conjugate acid of the base by about 25% or less.

30. The method of claim 26, wherein the pKa of the solvent is about 16 to about 20.

31. The method of claim 26, wherein the ratio of the diastereomeric form of (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine to that of (3S,6S)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine in the solid phase is at least about 75:25, preferably about 90:

10.

32. A method comprising: (2S)-6-cyano-5-hexen-1-ol-2-amine, having a protecting group on its amine, is reacted with an alkoxide base in an alcoholic solvent to produce a reaction mixture containing a solid phase, wherein: The solid phase comprises a diastereomeric mixture of (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine and (3S,6S)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine having a protecting group on the amine; and The ratio of the diastereomeric form of the solid phase having a protecting group on the amine (3S,6R)-6-(cyanomethyl)-tetrahydro-2H-pyran-3-amine to the diastereomeric form of the amine having a protecting group on the amine is at least about 75:

25.

33. The method of claim 32, wherein the reaction is carried out until at least about 80% of APA-7 is converted to APA-8.

34. The method of claim 32, wherein the reaction is carried out at about 10°C-50°C. 0 At a temperature of C, choose any temperature between 20℃ and 30℃. 0 Perform under C.

35. The method of claim 32, wherein the reaction mixture is stirred or agitated while the reaction is being carried out.

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