Method for the synthesis of 1,4-dihydronicotinamide riboside (NRH) from nicotinamide-β-riboside triacetate chloride (NRA-Cl)

Abstract

The present invention discloses a novel synthesis process for 1,4-dihydronicotinamide riboside (NRH). More specifically, the present invention discloses a cost-effective, good yield and purity synthesis of 1,4-dihydronicotinamide riboside (NRH) from nicotinamide-β-riboside triacetate chloride (NRA-Cl), comprising: a) reducing nicotinamide-β-riboside triacetate chloride (NRA-Cl) in the presence of a non-chlorinated aprotic organic solvent and a reducing agent to obtain 1,4-dihydronicotinamide riboside triacetate (NRH-A); and b) deacetylating 1,4-dihydronicotinamide riboside triacetate (NRHA) in the presence of a base to obtain 1,4-dihydronicotinamide riboside (NRH).

Description

[Technical field]

[0001] The present invention relates to a novel method for the synthesis of 1,4-dihydronicotinamide riboside (NRH), more specifically, the present invention relates to a cost-effective synthesis of 1,4-dihydronicotinamide riboside (NRH) from nicotinamide-beta-riboside triacetate chloride (NRA-Cl) in good yield and purity. [Background technology]

[0002] Nicotinamide riboside and its derivatives, including nicotinic acid riboside, nicotinamide mononucleotide, and nicotinic acid mononucleotide, are metabolites of nicotinamide adenine dinucleotide (NAD+). Nicotinamide adenine dinucleotide (NAD+) and its reduced form, 1,4-dihydronicotinamide adenine dinucleotide (NADH), are important molecules in energy metabolism and mitochondrial function via electron transport. Thus, interest in pharmacological agents that can increase intracellular NAD+ concentrations has stimulated research into nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN). However, NR and NMN require large doses to increase intracellular NAD+ concentrations. Sauve et al. synthesized 1,4-dihydronicotinamide riboside (NRH) and demonstrated that NRH strongly increases NAD+ concentration both in vitro and in vivo, and further reported that NRH increases NAD+ concentration in mammalian cells by 2.5 to 10 times the control value in just 1 hour. Sauve et al. also demonstrated that the use of NRH is more effective than either NR or NMN alone.

[0003] Subsequently, Canto et al. discovered that, in contrast to the NR pathway, the NRH pathway synthesizes NAD+ using different steps and enzymes, and further demonstrated that NRH is orally bioavailable as an NAD+ precursor.

[0004] Since NRH is gaining importance over NR or NMN, industrially useful syntheses of this molecule have also attracted the attention of the research community.

[0005] There is ample literature available on methods for the preparation of NRH.

[0006] NJ Oppenheimer et al. reported the synthesis of NRH from dihydronicotinamide mononucleotide (NMNH) by hydrolysis of the 5'-phosphate in the presence of alkaline phosphatase. However, this method is time-consuming and requires enzymes, so it is not cost-effective. Therefore, Oppenheimer's method is not suitable for industrial production of NRH (Non-Patent Document 1).

[0007] MVMakarov et al. (Non-Patent Document 2) reported a two-step method for the synthesis of NRH by using triacetylated nicotinamide riboside triflate as the starting material. In the first step, triacetylated NR is converted to triacetylated NRH by reduction with Na2S2O4. In the second step, NRH is produced by methanolysis of triacetylated NRH while grinding in a ball mill. Although this method is promising as it gives good yields of NRH, the use of triacetylated nicotinamide riboside triflate, an expensive and non-food grade material due to the presence of triflate anion, limits the scalability of this method. The method reported by MVMakarov et al. is shown in Scheme 1 below.

[0008] [ka]

[0009] Y. Yang et al. reported another method for the synthesis of NRH by reduction of NR triflate in the presence of sodium dithionate (Na2S2O4) and potassium hydrogen phosphate as reducing agents (Non-Patent Document 3). Since NRH is susceptible to both hydrolysis and oxidation under ambient conditions, the crude NRH thus obtained is immediately purified by HPLC using a C18 resin column. The method reported by Yang et al. gives NRH in 70% yield. This method is shown in Scheme 2 below.

[0010] [ka]

[0011] The drawbacks associated with the above methods include: a) the precursor nicotinamide riboside triflate is not only expensive but also highly hygroscopic and therefore must be stored at about −20° C. under an inert atmosphere, which adds additional costs to the production; and b) Nicotinamide riboside triflate is not food grade due to the presence of triflate anion, therefore, column purification of NRH is required to completely remove the triflate anion, thus increasing the cost of the manufacturing process; There is.

[0012] Amin Zarei et al. (Non-Patent Document 4) reported a straightforward method for the scalable synthesis of NRH by using commercially available β-NRCl. In this method, β-NRCl is reduced in an aqueous solution of NaHCO3 and Na2S2O4 under nitrogen atmosphere. However, this method has the drawback that the resulting product, NRH, needs to be purified from the reaction mixture by column chromatography to obtain the product in 55% yield and 96% purity. Furthermore, NRCl has been reported to be an unstable molecule that decomposes when exposed to high temperatures and requires careful storage and handling. The synthesis reported in this paper is shown below in Scheme 3.

[0013] [ka]

[0014] US Pat. No. 5,399,436 discloses that triacetylated NR triflate is reacted with sodium dithionite to obtain triacetylated NRH, which is deacetylated by treating with a base such as sodium methoxide in MeOH to obtain NRH. The process reported in US Pat. No. 5,399,436 is also not suitable for industrial use because triacetylated NR triflate is expensive and is not food grade due to triflate ions, and thus the NRH obtained in this way requires extensive purification to be free of triflate anions. The synthesis is shown in Scheme 4 below.

[0015] [ka]

[0016] In Example 1A and Example 1C of Patent Document 2, it is disclosed that triacetylated NR triflate or tribenzoylated NR triflate is reacted with sodium dithionite to obtain triacetylated NRH. In Example 2 of Patent Document 2, it is disclosed that triacetylated NRH / tribenzoylated NRH is deprotected by using a base such as sodium hydroxide in MeOH in a mechanochemical process as shown in Scheme 5 below. This process also requires additional equipment and column chromatography purification, and therefore is not industrially scalable.

[0017] [ka]

[0018] In view of the above, there remains a need in the art to provide a process for the preparation of NRH in a yield of at least 85-99% and with a purity of at least 98% or more in a cost-effective manner, and thus, may be commercially scalable. [Prior art documents] [Patent documents]

[0019] [Patent Document 1] International Publication No. 2017 / 079195 Brochure [Patent Document 2] International Publication No. 2015 / 014722 Brochure [Non-patent literature]

[0020] [Non-Patent Document 1] N.J. Oppenheimer et al., Biochemistry, 1976, Vol. 15, pp. 3981-3989 [Non-Patent Document 2] MV Makarov et al., Organic and Biomolecular Chemistry, 2019, Vol. 17, pp. 8716-8720 [Non-Patent Document 3] Y. Yang et al., Journal of Biological Chemistry, 2019, Vol. 294, pp. 9295-9307 [Non-Patent Document 4] Amin Zarei et al., [online], Internet<DOI:https: / / doi.org / 10.1039 / D1RA02062E> Summary of the Invention [Problem to be solved by the invention]

[0021] Therefore, it is an object of the present invention to provide a method for the preparation of 1,4-dihydronicotinamide riboside (NRH) using the cost-effective starting material nicotinamide-beta-riboside triacetate chloride (NRA-Cl). [Means for solving the problem]

[0022] In accordance with the above objectives, the present invention provides a method for preparing 1,4-dihydronicotinamide riboside (NRH), comprising the steps of: a) reducing nicotinamide-beta-riboside triacetate chloride (NRA-Cl) in the presence of non-chlorinated aprotic organic solvent(s) and a reducing agent to obtain 1,4-dihydronicotinamide riboside triacetate (NRH-A); b) deacetylating 1,4-dihydronicotinamide riboside triacetate (NRH-A) in the presence of a base to obtain 1,4-dihydronicotinamide riboside (NRH); The present invention provides a method comprising:

[0023] In one aspect, the reducing agent may be selected from the group consisting of sodium dithionite (Na2S2O4) or thiourea dioxide (TDO).

[0024] The non-chlorinated aprotic organic solvent for reducing NRA-Cl may be selected from the group consisting of cyclic and acyclic ethers such as 2-methyltetrahydrofuran (2-MeTHF), t-butylmethyl ether (TBME), diisopropyl ether, diethyl ether, cyclopentyl methyl ether, esters such as ethyl acetate (EtOAc), methyl acetate, propyl acetate, butyl acetate, and cyclic and acyclic hydrocarbon solvents such as cyclohexane, cycloheptane, n-hexane, n-heptane, benzene, xylene, trimethylbenzene, and toluene. In particular, non-aqueous solvents are preferred because the reaction occurs in a two-phase solvent system.

[0025] Bases that may be used for the deacetylation of NRH-Ais are selected from the group consisting of 0.1% NaOH in MeOH, 0.1% NaOMe in MeOH, 1 mol% K2CO3 in methanol, 7% methanolic NH3 and 10% aqueous NH3, or dialkylamines such as N,N-dimethylamine or N,N-diethylamine or N,N-dibutylamine, or cyclic secondary amines such as pyrrolidine, morpholine and piperidine in protic solvents such as methanol, ethanol and isopropanol. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1H NMR of NRH-OAc prepared according to Example 2. [Diagram 2] FIG. 13C NMR-NRH-OAc prepared according to Example 2. [Diagram 3] FIG. 1H NMR of NRH prepared according to Example 3. [Figure 4] FIG. 13C NMR-NRH prepared according to Example 3. [Diagram 5] FIG. 1 shows an HPLC chromatogram of NRH prepared according to Example 3. [Figure 6] FIG. 1 shows the mass spectrum of NRH prepared according to Example 3. [Figure 7] FIG. 1 shows the PXRD of NRH prepared according to Example 3, indicating the amorphous nature of the compound. [Figure 8] FIG. 1 shows HRMS of NRH prepared according to Example 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Detailed Description of the Invention The present invention will now be described in detail with reference to certain preferred and optional embodiments so that its various aspects may be fully understood and appreciated.

[0028] Accordingly, the present invention provides a method for preparing 1,4-dihydronicotinamide riboside (NRH), comprising the steps of: a) reducing nicotinamide-beta-riboside triacetate chloride (NRA-Cl) in the presence of non-chlorinated aprotic organic solvent(s) and a reducing agent to obtain 1,4-dihydronicotinamide riboside triacetate (NRH-A); b) deacetylating 1,4-dihydronicotinamide riboside triacetate (NRH-A) in the presence of a base to obtain 1,4-dihydronicotinamide riboside (NRH); The present invention provides a method comprising:

[0029] According to one embodiment, reduction of nicotinamide-beta-riboside triacetate chloride (NRA-Cl) was carried out with sodium dithionite (NaSO) in the presence of a saturated solution of NaHCO under a nitrogen atmosphere in the presence of a suitable non-chlorinated organic solvent.

[0030] The non-chlorinated aprotic organic solvent for reducing NRA-Cl may be selected from the group consisting of cyclic and acyclic ethers such as 2-methyltetrahydrofuran (2-MeTHF), t-butylmethyl ether (TBME), diisopropyl ether, diethyl ether, cyclopentyl methyl ether, and the like; esters such as ethyl acetate (EtOAc), methyl acetate, propyl acetate, butyl acetate, and the like; and cyclic and acyclic hydrocarbon solvents such as cyclohexane, cycloheptane, n-hexane, n-heptane, benzene, xylene, trimethylbenzene, and toluene.

[0031] More specifically, the non-chlorinated organic solvent for this reaction may be selected from the group consisting of 2-methyltetrahydrofuran (2-MeTHF), t-butylmethyl ether (TBME), ethyl acetate (EtOAc), cyclohexane and toluene. The reduction reaction may be suitably carried out at room temperature to the reflux temperature of the solvent used. Preferably, the reduction reaction was carried out at room temperature for 4 to 5 hours with stirring. After completion of the reaction, the product 1,4-dihydronicotinamide riboside triacetate (NRH-A) was recovered from the organic phase.

[0032] In one preferred embodiment, the suitable non-chlorinated organic solvent is selected from 2-methyl THF or ethyl acetate. 2-methyl THF is a particularly useful solvent among various ethers, which is a green solvent, recoverable and reusable, and furthermore, the solvent provides the product in quantitative yield with excellent purity. Thus, the present invention has demonstrated that NRA-Cl can be converted to NRH-A without using chlorinated solvents such as DCM and DCE.

[0033] The reduction of nicotinamide-β-riboside triacetate chloride can occur in yields of 70% or more in toluene, 75% or more in diethyl ether, 80% or more in tert-butyl methyl ether, 95% or more in ethyl acetate, or 90% or more in 2-methyl THF. The reduction of nicotinamide-β-riboside triacetate chloride can produce 1,4-dihydronicotinamide riboside triacetate in purities of 85% or more in toluene, 90% or more in cyclohexane, and 98% or more in 2-methyl THF or ethyl acetate. The thus obtained NRH-A was further deacetylated in the presence of a suitable base at room temperature. After TLC (MeOH:DCM 2:8) showed the complete disappearance of the starting material, the solvent was evaporated and the thus obtained viscous mass was washed twice with acetone and then dried under vacuum for 1-2 hours to obtain NRH as a pale yellow solid. The base for this deacetylation reaction may be selected from the group consisting of 0.1% NaOH in MeOH, 0.1% NaOMe in MeOH, 1 mol% K2CO3 in methanol, 7% methanolic NH3, and 10% aqueous NH3.

[0034] In one preferred embodiment, the base is 0.1% sodium methoxide in methanol.

[0035] Deacetylation of 1,4-dihydronicotinamide riboside triacetate can occur with ammonia in methanol in yields of 80% or greater, K2CO3 in methanol in yields of 85% or greater, NaOH in methanol in yields of 90% or greater, or NaOMe in methanol in yields of 96% or greater. Deacetylation of 1,4-dihydronicotinamide riboside triacetate can produce NRHwith purity of 90% or greater with K2CO3, 95% or greater with NaOMe, or 98% or greater with NaOH.

[0036] In another preferred embodiment, the reduction of Nicotinamide-beta-riboside triacetate chloride (NRA-Cl) was carried out with thiourea dioxide in the presence of a suitable non-chlorinated aprotic organic solvent in a saturated state. A solution of NaHCO3 as a base under a nitrogen atmosphere. The reduction reaction can be suitably carried out at room temperature to the reflux temperature of the solvent used, but the reduction reaction was preferably carried out at room temperature for 6 to 8 hours with stirring. After the reaction was completed, the product NRH-A was recovered from the organic phase. Cyclic and acyclic ethers, such as diethyl ether, diisopropyl ether, THF, 2-methyltetrahydrofuran, and t-butylmethyl ether (TBME); cyclopentyl methyl ether; Esters, for example, C1-C6 alkyl esters of C1-C6 carboxylic acids such as ethyl acetate, methyl acetate, propyl acetate, and butyl acetate; C1-C10 cyclic alkanes; e.g., cyclohexane, cycloheptane C1-C10 acyclic alkanes; for example, n-hexane, n-heptane, and Aromatic hydrocarbons, such as benzene, toluene, xylene and trimethylbenzene Non-chlorinated aprotic organic solvents that may be used in this reaction include:

[0037] In various embodiments, exemplary non-halogenated aprotic organic solvents that may be used in the reduction of nicotinamide-β-riboside triacetate chloride include 2-methyltetrahydrofuran (2-MeTHF), t-butylmethyl ether (TBME), ethyl acetate (EtOAc), cyclohexane, and toluene.

[0038] Thiourea dioxide is a readily available reducing reagent for the selective 1,4-reduction of NRA-Cl under extremely mild conditions. In one preferred embodiment, the reaction was carried out in 2-methyl-THF solvent, which afforded the product in good yield with excellent purity.

[0039] Further, the thus obtained NRH-A was deacetylated in the presence of a suitable base at room temperature. After TLC (MeOH:DCM 2:8) showed the complete disappearance of the starting material, the solvent was evaporated and the viscous mass was washed with acetone twice, then dried under vacuum for 1-2 hours to obtain NRH as a pale yellow solid. The base that can be used for this deacetylation reaction is selected from the group consisting of 0.1% NaOH in MeOH, 0.1% NaOMe in MeOH, 1 mol% K2CO3 in methanol, 7% methanolic NH3, 10% aqueous NH3, and anhydrous HCl in methanol.

[0040] In one preferred embodiment, the base is 0.1% sodium methoxide in methanol.

[0041] The starting material β-NRCl-OAc used in the synthesis of NRH in the present invention is stable at room temperature, therefore, the material is easier to handle and does not require special conditions for storage. Furthermore, the use of β-NRCl-OAc allows the production of NRH-A in 85-95% yield and NRH in 90-95% yield and 90-98% purity, compared to the reported processes. In the process of the present invention, the intermediate NRH-A and the final product NRH can be easily separated from the organic phase by utilizing a careful selection of solvents, without subjecting them to column chromatographic purification, unlike the teachings of the prior art. Moreover, the entire process can be carried out at room temperature, thereby avoiding the need for additional energy sources. Thus, the process of the present invention for the synthesis of NRH is cost-effective and therefore scalable to industrial scale.

[0042] The present invention will now be described with reference to examples. The above-mentioned embodiments and the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Various modifications of the above-mentioned embodiments and the following examples will be readily apparent to those skilled in the art. EXAMPLES

[0043] Example 1 Synthesis of NRH-A from NRA-Cl using Na2S2O4 in 2-methylTHF Phase 1: Reduction of NRA-Cl using sodium dithionite (Na2S2O4) [ka]

[0044] To NRA-Cl (2.8 g, 7.4 mmol) dissolved in 40 mL of nitrogen-purged 2-methyl-THF under N2 atmosphere was added saturated NaHCO3 solution (13 mL) and solid sodium dithionite (4.17 g, 24 mmol) solution followed by 5 mL of water at 25 °C. The resulting mixture was stirred at the same temperature for 4-5 h. The progress was monitored by TLC using 1% methanol in ethyl acetate or 1% methanol in DCM as mobile phase and the TLC spots were visualized with anisaldehyde solution. The organic phase was separated and the aqueous phase was extracted with 40 mL of 2-methyl-THF. The combined organic layers were washed with saturated brine, dried over sodium sulfate and concentrated under reduced pressure to give a pale yellow solid (NRH-A) in 90% yield with purity of >98%.

[0045] Example 2 Synthesis of NRH from NRH-A using Na2S2O4 in ethyl acetate Phase 1: Reduction of NRA-Cl using sodium dithionite (Na2S2O4) [ka]

[0046] A 3 L, 3-neck RB flask equipped with a magnetic stirrer was charged with ethyl acetate (1400 mL), purged with nitrogen for 30 minutes, NRA-Cl (100 g) was added, and the contents were stirred for 10 minutes. To this solution with stirring at 25° C. was added saturated sodium bicarbonate solution (464 mL) (RM turned pale yellow), followed by slow addition of sodium dithionite (solid, 148.9 g) (reaction mixture turned pale yellow cloudy solution). DM water (250 mL) was added slowly to get a clear solution and the contents were stirred at room temperature for 2 h and monitored by TLC (5% methanol:95% DCM, TLC spots were visualized by anisaldehyde solution or 10% H2SO4 in methanol. After completion of the reaction, the organic layer was separated, washed with saturated brine (500 mL), dried over Na2SO4, and evaporated under reduced pressure while maintaining the bath temperature below 39-40 °C to give 88 g of pale yellow solid product (yield 95.8%).

[0047] NRH-OAc 1 HNMR and 13 The C NMR spectra are shown in Figures 1 and 2, respectively.

[0048] Similarly, reduction of NRA-Cl with sodium dithionite (Na2S2O4) was carried out in various other solvents such as t-butyl methyl ether (TBME), cyclohexane and toluene. As shown in Table 1 below, reduction of NRA-Cl with sodium dithionite (Na2S2O4) gives 90% yield in 2-methyl-THF, 95.8% yield in ethyl acetate, 75% yield in t-butyl methyl ether (TBME), 70% yield in cyclohexane and 65% yield in toluene. Moreover, all of these solvents give the product NRA-H with purity ranging from 85% to 98%. The reaction is carried out at a temperature of 25-30°C.

[0049] [Table 1]

[0050] All of these solvents were found to be suitable as they afforded NRH-A in good yields and are therefore useful for the industrial production of NRH-A.

[0051] Phase 2: Deacetylation of NRH-A(2) with sodium methoxide in methanol [ka]

[0052] To a stirred solution of 2 (80 gm) obtained by the process of Example 1 and Example 2 above in methanol (400 mL) was added sodium methoxide (1.15 g) at 25° C. The resulting solution was stirred at the same temperature for 3-4 hours. Upon complete disappearance of starting material as indicated by TLC (MeOH:DCM 2:8). The organic layer was distilled under reduced pressure maintaining the bath temperature below 39-40° C. to give 52 g of pale yellow solid product (97% yield).

[0053] purification: The pale yellow solid product, NRH (50 g), was dissolved in 500 mL of acetone and stirred vigorously for 30 min. After 30 min, the product was filtered under a strict nitrogen atmosphere and washed with 250 mL of acetone. The filtered product was dried under a nitrogen atmosphere to give an amorphous powder. Purity: 99.97% by Shimadzu HPLC using Lab solutions software

[0054] The 1H NMR, 13C NMR, HPLC chromatogram, mass spectrum, PXRD and HRMS of NRH are shown in Figures 3 to 8, respectively.

[0055] Similarly, the deacetylation reaction was also carried out using different bases such as 0.1% NaOH in MeOH, 1 mol% K2CO3 in methanol, 7% methanolic NH3, and 10% aqueous NH3, and gave the product NRH in very good yields, indicating that these bases are suitable for the industrial scalability of the reaction.

[0056] Example 3: Synthesis of NRH from NRA-Cl using thiourea dioxide (TDO) in 2-MeTHF Phase 1: Reduction of NRA-Cl with TDO [ka]

[0057] To NRA-Cl (2.8 g, 7.4 mmol) dissolved in 40 mL of nitrogen-purged 2-methyl-THF under N2 atmosphere was added a saturated solution of NaHCO3 (13 mL) and solid TDO (1.59 g, 14.8 mmol) at 25 °C. The resulting mixture was stirred at the same temperature for 6-8 h. The organic phase was separated and the aqueous phase was extracted with 40 mL of 2-methyl-THF. The combined organic layers were washed with saturated brine, dried over sodium sulfate, and concentrated under reduced pressure to give a pale yellow solid (NRH-A) in 82% yield with a purity of >98%.

[0058] Similarly, reduction of NRA-Cl with Thiourea Dioxide (TDO) was carried out in various solvents, giving yields of 75% in t-butylmethyl ether (TBME), 80% in ethyl acetate (EtOAc), 70% in cyclohexane, and 65% in toluene. All of these solvents afforded NRH-A in good yield and purity (Table 1), proving that they are suitable for industrial production of NRH-A.

[0059] Similarly, reduction reactions were carried out with different bases to give NRH-A in yields of 85% with aqueous NH3, 80% with alcoholic NH3, 65% with K2HPO4, and 60% with K3PO4. However, concomitant hydrolysis of the acetate ester was also observed with aqueous NH3 or alcoholic NH3. Aqueous NH3 or alcoholic NH3 reduced NRA-Cl and deprotected the acetate group.

[0060] Phase 2: Deacetylation of NRH-A(2) with sodium methoxide [ka]

[0061] To a stirred solution of 2 (80 g) in methanol (400 mL) was added sodium methoxide (1.15 g) at 25 °C. The resulting solution was stirred at the same temperature for 3-4 h. After TLC (MeOH:DCM 2:8) showed complete disappearance of the starting material, the organic layer was distilled under reduced pressure while maintaining the bath temperature below 39-40 °C to give 52 g of pale yellow solid product (97% yield).

[0062] purification: The pale yellow solid product, NRH (50 g), was dissolved in 500 mL (10 volumes) of acetone and stirred vigorously for 30 min. After 30 min, the product was filtered under a strict nitrogen atmosphere and washed with 250 mL (5 volumes) of acetone. The filtered product was dried under a nitrogen atmosphere and transferred to a flame-dried, nitrogen-flushed vial. Purity: 99.97% by Shimadzu HPLC using Lab solutions software

[0063] Similarly, the deacetylation reaction was carried out with different bases to give NRH in yields of over 95% with 0.1% NaOH or NaOMe in MeOH, 85% with 1 mol% K2CO3 in methanol, 90% with 7% methanolic NH3, and 87% with 10% aqueous NH3, demonstrating the suitability of these bases and the scalability of this reaction. [Industrial Applicability]

[0064] The starting material, β-NRCl-OAc, is stable at room temperature, therefore this material is easier to handle and does not require special conditions for storage.

[0065] Furthermore, the use of β-NRCl-OAc affords NRH-A and NRH in good yields and purity compared to reported processes.

[0066] In the process of the present invention, unlike the teachings of the prior art, the intermediate NRH-A and the final product NRH can be easily separated from the organic phase by utilizing a careful selection of solvents without column chromatography purification. The process can be carried out at room temperature and pressure, thus avoiding the need for an energy source to carry out the reaction. The NRH obtained by the process of the present invention is essentially amorphous and of high purity (>99.97% by HPLC).

[0067] Therefore, the process of the present invention for the synthesis of NRH is cost-effective and therefore scalable to industrial scale.

Claims

1. a) reducing nicotinamide-β-riboside triacetate chloride (NRA-Cl) in the presence of a non-chlorinated aprotic organic solvent and a reducing agent to obtain 1,4-dihydronicotinamide riboside triacetate (NRH-A); b) deacetylating the 1,4-dihydronicotinamide riboside triacetate (NRH-A) in the presence of a base to obtain 1,4-dihydronicotinamide riboside (NRH); 1. A method for preparing 1,4-dihydronicotinamide riboside (NRH), comprising:

2. The reducing agent is sodium dithionite (Na ２ S ２ O ４ 2. The method of claim 1, wherein the thiourea dioxide (TDO) is selected from the group consisting of thiourea dioxide (TDO) and thiourea dioxide (TDO).

3. The reducing agent is sodium dithionite (Na ２ S ２ O ４ 2. The method of claim 1 , wherein

4. The method of claim 1 , wherein the reducing agent is thiourea dioxide (TDO).

5. 2. The method of claim 1, wherein the non-chlorinated aprotic organic solvent is selected from the group consisting of cyclic and acyclic ethers, esters, C1-C10 cyclic alkanes, C1-C10 acyclic alkanes, and aromatic hydrocarbons.

6. 6. The method of claim 5, wherein the cyclic and acyclic ethers are selected from the group consisting of diethyl ether, diisopropyl ether, THF, 2-methyltetrahydrofuran, and t-butyl methyl ether (TBME) and cyclopentyl methyl ether.

7. 6. The method of claim 5, wherein the ester is selected from the group consisting of C1 to C6 alkyl esters of C1 to C6 carboxylic acids, such as ethyl acetate, methyl acetate, propyl acetate, and butyl acetate.

8. 6. The method of claim 5, wherein the C1-C10 cyclic alkane is selected from cyclohexane, cycloheptane, and the C1-C10 acyclic alkane is selected from n-hexane and n-heptane.

9. 6. The method of claim 5, wherein the aromatic hydrocarbon is selected from benzene, toluene, xylene and trimethylbenzene.

10. The base for deacetylation of NRH-A was 0.1% NaOH in MeOH, 0.1% NaOMe in MeOH, 1 mol% K in methanol. ２ CO ３ , 7% methanolic NH ３ , and 10% NH ３ 2. The method of claim 1, wherein the amine is selected from the group consisting of dialkylamines such as N,N-dimethylamine, N,N-diethylamine or N,N-dibutylamine in aqueous solution or in protic solvents such as methanol, ethanol and isopropanol, or cyclic secondary amines such as pyrrolidine, morpholine and piperidine.

11. 10. The process according to claim 1, wherein the reduction reaction is suitably carried out at from room temperature to the reflux temperature of the solvent used.

12. 12. The process according to any one of claims 1 to 11, wherein the reduction reaction is carried out in a non-chlorinated organic solvent selected from the group consisting of 2-methyltetrahydrofuran (2-MeTHF), t-butyl methyl ether (TBME), ethyl acetate (EtOAc), cyclohexane, and toluene.

13. The method of claim 12, wherein the non-chlorinated organic solvent is selected from 2-methyl-THF or ethyl acetate.

14. 14. The process according to any one of claims 1 to 13, wherein the base is 0.1% sodium methoxide in methanol.

15. The reduction reaction is carried out using NaHCO, NH ３ Aqueous solution; Alcoholic NH3 solution; K ２ H.P.O. ４ and K. ３ P.O. ４ The process according to any one of claims 1 to 14, carried out in the presence of a base selected from the group consisting of:

16. The reduction reaction is carried out with NaHCO ３ 16. The process of claim 15, carried out in the presence of a saturated solution of

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