A method for synthesizing N-glycosides without protective sugars

Abstract

This invention relates to the field of chemical synthesis technology, and more specifically to a method for synthesizing N-glycosides from unprotected sugars. The method is characterized by dissolving an unprotected glycosyl donor, acceptor, and base in water or a mixture of water and an organic solvent at temperatures ranging from -78°C to 25°C, adding a promoter, and reacting to obtain the corresponding glycoside. This invention synthesizes a series of DMC analogs, which are previously unreported and are novel compounds. These analogs can mediate the glycosylation of unprotected sugars with a base as the acceptor, and can also specifically bind to the 9-N position of the acceptor. This method avoids the complex operations of upper and lower protecting groups, and the glycosylation reaction product exhibits high stereoselectivity, significantly reducing the complexity and cost of glycosylation synthesis.

Description

Technical Field

[0001] This invention relates to chemical synthesis, and more specifically to a method for synthesizing N-glycosides without protective sugars. Background Technology

[0002] Sugars, also known as carbohydrates, are one of the four important biological macromolecules in life processes, along with proteins, nucleic acids, and lipids. They are widely distributed in plants, animals, microorganisms, and viruses. Sugars exist in the form of monosaccharides, oligosaccharides, polysaccharides, and glycoconjugates. Currently, there are two main methods for the in vitro synthesis of sugars: enzymatic synthesis and chemical synthesis. Although enzymatic synthesis has advantages such as mild reaction and good regio and stereoselectivity, the required glycosyltransferases and glycosidases are relatively expensive. In addition, the enzymes have poor acceptance of non-natural or abnormal substrates. Therefore, chemical synthesis of sugars is indispensable. However, existing glycosylation methods still have many shortcomings. To date, no glycosylation method is universally applicable to the synthesis of all oligosaccharides. Furthermore, existing glycosylation synthesis involves a large number of experimental operations involving adding and removing protecting groups, and the extended synthetic steps increase the complexity of the synthesis. Therefore, it is of great significance to study new one-pot glycosylation methods for unprotected sugars in aqueous phase.

[0003] 2-Chloro-1,3-dimethylimidazoline chloride (DMC) was developed by Isobe and Ishikawathe in the late 1990s as a dehydrating agent to replace DCC. In 2009, Shoda et al. first introduced DMC into the carbohydrate field and revealed its ability to selectively activate the anomeric hydroxyl groups of unprotected sugars in aqueous solution. To date, DMC has been successfully applied to the synthesis of glycosyl oxazolines, the production of 1,6-anhydrous sugars, the synthesis of glycosyl azides, and glycosyl thiols, but no reports have been found on its application to N-glycosides.

[0004] Summary of the Invention

[0005] Purpose of the invention

[0006] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide a method for the synthesis of unprotected sugars via N-glycosylation mediated by DMC and its analogues.

[0007] Technical solution

[0008] A method for synthesizing N-glycosides from unprotected sugars, characterized in that, under conditions of -78℃ to 25℃, an unprotected sugar donor, an acceptor, and a base are dissolved in water or a mixture of water and an organic solvent, an accelerator is added, and the reaction yields the corresponding glycoside. The general reaction formula is as follows:

[0009]

[0010] The glycosyl donor is a pyranose, furanose, disaccharide, polysaccharide, or a glycosyl analogue;

[0011] The receptor is a nitrogen heterocyclic compound or an organic amine;

[0012] The base is triethylamine or DIPEA;

[0013] The accelerator is selected from any one of the following structures:

[0014]

[0015] The method is characterized in that,

[0016] Pyranose can be ribose, arabinose, or 2-deoxyribose;

[0017] Furanose can be glucose, galactose, mannose, fucose, xylose, arabinose, N-acetylglucosamine, or rhamnose.

[0018] The disaccharide is lactose, maltose, or cellobiose;

[0019] The sugar structure analogue is tetrahydro-2H-pyran-2-ol.

[0020] The method is characterized in that, when the acceptor is a nitrogen heterocyclic compound, it is selected from compounds with any of the following structures:

[0021]

[0022] Wherein, R1 is hydrogen, fluorine, chlorine, bromine, iodine, amino, nitrogen acetyl, nitrogen benzoyl, NHBoc, or N(Boc)2; R2 is hydrogen, fluorine, chlorine, bromine, iodine, amino, nitrogen acetyl, nitrogen benzoyl, NHBoc, or N(Boc)2; R3 is hydrogen, hydroxyl, carboxyl, methyl formate, nitro, amino, fluorine, chlorine, bromine, or iodine; R4 is hydrogen, hydroxyl, carboxyl, methyl formate, nitro, amino, fluorine, chlorine, bromine, or iodine.

[0023] When the acceptor is an organic amine, it includes straight-chain amine and aromatic amine. The straight-chain amine is n-butylamine, and the aromatic amine is aniline, p-methylaniline, or p-methoxyaniline.

[0024] The method is characterized in that the mixed solvent of water and organic solvent is any one of the following: a mixed reagent of water and tetrahydrofuran, a mixed reagent of water and 1,4-dioxane, a mixed reagent of water and acetonitrile, a mixed reagent of water and DMF, a mixed reagent of water and DMSO, or a mixed reagent of water and acetone.

[0025] The method is characterized in that:

[0026] The molar ratio of the glycosyl donor to the acceptor is 1:1.1 to 1:10; the molar ratio of the glycosyl donor to the promoter is 1:1.5 to 1:5; and the molar ratio of the glycosyl donor to the base is 1:5 to 1:20.

[0027] The method is characterized in that the volume ratio of the mixed solvents in the reaction solvent is 1:0 to 1:5.

[0028] The method is characterized in that the temperature is -10℃.

[0029] In some embodiments of the present invention, the molar ratio of glycosyl donor to acceptor is 1:1.1 to 1:10, preferably 1:5; the molar ratio of glycosyl donor to promoter is 1:1.5 to 1:5, preferably 1:3; the molar ratio of glycosyl donor to base is 1:5 to 1:20, preferably 1:5 to 1:10, and most preferably 1:10.

[0030] In some embodiments of the present invention, the reaction solvent is any one of water, a mixture of water and tetrahydrofuran, a mixture of water and 1,4-dioxane, a mixture of water and acetonitrile, a mixture of water and DMF, a mixture of water and DMSO, or a mixture of water and acetone, preferably a mixture of water and tetrahydrofuran or a mixture of water and 1,4-dioxane.

[0031] In some embodiments of the present invention, the mixing ratio (volume ratio) of the reaction solvent is preferably V. 水 V 有机试剂 =1:0 to 1:1, the optimal value is V 水 V 有机试剂 =1:1;

[0032] In some embodiments of the present invention, considering the ease of subsequent separation, purification, and structural stability, the aqueous glycosylation product is subjected to acetylation. The process is characterized by: dissolving the aqueous glycosylation product in anhydrous pyridine at 0°C, slowly adding acetic anhydride, reacting overnight at room temperature, washing the reaction solution with 1N dilute hydrochloric acid, extracting the reaction solution three times with EA, combining the organic phases, washing the organic phases with water, saturated sodium bicarbonate, and brine, drying with anhydrous sodium sulfate, filtering, and purifying by column chromatography.

[0033] Furthermore, the molar ratio of the aqueous glycosylation product to pyridine is 1:5 to 1:30, preferably 1:10; the molar ratio of the aqueous glycosylation product to acetic anhydride is 1:4 to 1:20, preferably 1:5.

[0034] To further inform the inventors, the following steps were taken for screening:

[0035] I. Screening of alkalis

[0036] In this system, the sugar is D-glucose, the acceptor is 6-chloropurine, the promoter is 1-1, and the solvent is water and 1,4-dioxane (V) 水 V 有机试剂 Taking a ratio of 1:1 and a temperature of -10℃ as examples, common bases are screened, and the general reaction formula is as follows:

[0037]

[0038] The results of the alkali screening are shown in Table 1.

[0039] Table 1. Screening of Alkali Types

[0040]

[0041] Note: Trace indicates a yield of less than 5%.

[0042] II. Screening of accelerators

[0043] The reaction was carried out using D-glucose as the sugar, 6-chloropurine as the acceptor, triethylamine as the base, at a temperature of -10°C, and water and 1,4-dioxane (V) as the solvent. 水 V 有机试剂 Taking a ratio of 1:1 as an example, the accelerators were screened, and the general reaction formula is as follows:

[0044]

[0045] The screening results are shown in Table 2.

[0046] Table 2. Accelerator Screening

[0047]

[0048]

[0049]

[0050] III. Screening of solvents and solvent ratios

[0051] Taking D-glucose as the sugar, 6-chloropurine as the acceptor, 1-1 as the promoter, triethylamine as the base, and a temperature of -10℃ as an example, the solvent and solvent ratio were screened, and the general reaction formula is as follows:

[0052]

[0053] The screening results are shown in Table 3.

[0054] Table 3. Solvent Screening

[0055]

[0056] IV. Screening for reaction temperature as a condition.

[0057] In some embodiments of the present invention, the temperature is -78°C to 25°C, preferably -40°C to -10°C, and most preferably -10°C. The sugar used is D-glucose, the acceptor is 6-chloropurine, the promoter is compound 1-1, the base is triethylamine, and the solvent is water and 1,4-dioxane (V... 水 V 有机试剂 Taking (e.g., 1:1) as an example, the reaction temperature is used to screen for this condition, and the general reaction formula is as follows:

[0058]

[0059] The screening results are shown in Table 4.

[0060] Table 4. Temperature Screening

[0061]

[0062] Beneficial effects:

[0063] 1. Existing technologies have shown that DMC has been successfully applied to the synthesis of glycosyl oxazolines, the production of 1,6-anhydrous sugars, the synthesis of glycosyl azides, and glycosyl thiols, but there are no literature reports on N-glycosides, especially those with nucleotide bases as receptors. For example, receptors such as purines have multiple N sites, but specifically bind to a particular site, such as position 9, without the need for a protecting group, which has always been a technical challenge in this field. This invention is the first to discover that under specific temperature and alkaline conditions, DMC can mediate the synthesis of N-glycosides (nucleotides) from unprotected sugars. It is important to note that this selective binding to the 9-position N receptor, rather than other N sites, is not reported in the literature.

[0064] 2. This invention synthesizes a series of DMC analogs, which are novel compounds not previously reported in the literature. These analogs can mediate the glycosylation of unprotected sugars with a receptor base, and can also specifically bind to the 9-position N of the receptor. This method avoids the complex operations of upper and lower protecting groups, and the glycosylation reaction product has high stereoselectivity, greatly reducing the complexity and cost of glycosylation synthesis.

[0065] Abbreviation Table

[0066] Boc tert-Butoxycarbonyl Bz benzoyl Ac Acetyl DCM dichloromethane PE petroleum ether EA Ethyl acetate THF Tetrahydrofuran DMF N,N-Dimethylformamide DMSO Dimethyl sulfoxide Dioxane 1,4-Dioxane MeOH methanol DBU 1,8-Diazabicyclo[5.4.0]undec-7-ene DIPEA Diisopropylethylamine DABCO Triethylenediamine TEA Triethylamine DMC 2-Chloro-1,3-dimethylimidazoline chloride CDMBI 2-Chloro-1,3-dimethyl-1H-benzimidazole-3-chloride NaOH Sodium hydroxide RT room temperature MeCN Acetonitrile

[0067] Terms and Explanations

[0068] In this invention, unless otherwise stated, the scientific and technical terms used herein have the meanings commonly understood by those skilled in the art. Furthermore, to better understand this invention, definitions and explanations of relevant terms are provided below.

[0069] All ranges described in this article include those endpoints that list the range between two values. Whether indicated or not, all values ​​listed in this article include the expected degree of experimental, technical, and instrumental error of the given technique used to measure that value.

[0070] In this invention, unless otherwise stated, % is a percentage of weight / weight (w / w).

[0071] In this invention, unless otherwise specified, the room temperature is 20–30°C, for example: 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30°C.

[0072] Unless otherwise stated, any numerical value, such as the concentration or concentration range described herein, should be understood to be modified by the term "about" in all cases. Therefore, numerical values ​​typically include ±10% of the stated value.

[0073] "Alkyl" refers to a saturated aliphatic hydrocarbon group, including straight-chain and branched groups with 1 to 10 carbon atoms, preferably including 1 to 6 carbon atoms. In this invention, non-limiting examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, n-pentyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, 1-ethylpropyl, 2-methylbutyl, 3-methylbutyl, n-hexyl, 1-ethyl-2-methylpropyl, 1,1,2-trimethylpropyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 2,2-dimethylbutyl, 1,3-dimethylbutyl, 2-ethylbutyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 2,3-dimethylbutyl, etc. The alkyl group may be substituted or unsubstituted. When substituted, the substituent may be replaced at any usable connection point, preferably one or more of the following groups, independently selected from alkyl, alkenyl, alkynyl, alkoxy, alkylthio, alkylamino, halogen, thiol, hydroxyl, nitro, cyano, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, cycloalkoxy, heterocycloalkoxy, cycloalkylthio, heterocycloalkylthio, and oxo. In some preferred embodiments of the invention, the alkyl group is methyl or ethyl. Attached Figure Description

[0074] Figure 1 The NMR spectrum of compound 1aa obtained in Example 1 is shown. Detailed Implementation

[0075] The present invention will be further described in detail below with reference to embodiments. It should be understood that the following description is exemplary only and does not limit its content. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods. Unless otherwise specified, the experimental materials used in the following embodiments were all purchased from conventional biochemical reagent stores.

[0076] Example 1:

[0077]

[0078] Synthesis of 1a:

[0079] Dissolve D-glucose (45 mg, 0.25 mmol) and 1-1 (228 mg, 0.75 mmol) in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-chloropurine (192.5 mg, 1.25 mmol) was added. The reaction was maintained at -10 °C, and TLC was monitored. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 1a in 58% yield.

[0080] Example 2:

[0081]

[0082] Synthesis of 1aa:

[0083] At 0°C, 1a was dissolved in anhydrous pyridine, and acetic anhydride was slowly added. The reaction was carried out overnight at room temperature. The reaction solution was washed with 1N dilute hydrochloric acid, and the reaction was extracted three times with EA. The organic phases were combined, washed with water, saturated sodium bicarbonate, and brine, dried over anhydrous sodium sulfate, and purified by column chromatography. The NMR spectrum is shown in S1, which is consistent with the results in previous reports.

[0084] 1 H NMR(300MHz,Chloroform-d)δ8.78(s,1H),8.34(s,1H),5.96(d,J=9.5Hz,1H),5.68(t,J=9.4Hz,1H),5.48(t,J=9.4Hz,1H), 5.31(t,J=9.7Hz,1H),4.30(dd,J=12.6,4.8Hz,1H),4.19–4.00(m,2H),2.08(s,3H),2.07(s,3H),2.04(s,3H),1.78(s,3H).

[0085] Example 3:

[0086]

[0087] Synthesis of 1a:

[0088] Dissolve D-glucose (45 mg, 0.25 mmol) and CDMBI (165 mg, 0.75 mmol) in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-chloropurine (192.5 mg, 1.25 mmol) was added. The reaction was maintained at -10 °C, and TLC was monitored. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 1a in 49% yield.

[0089] Example 4:

[0090]

[0091] Synthesis of 1a:

[0092] Dissolve D-glucose (45 mg, 0.25 mmol) and 1-4 (127.5 mg, 0.75 mmol) in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-chloropurine (192.5 mg, 1.25 mmol) was added. The mixture was maintained at -10 °C and monitored by TLC. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 1a in 17% yield.

[0093] Example 5:

[0094]

[0095] Synthesis of 1a:

[0096] Dissolve D-glucose (45 mg, 0.25 mmol) and 1-5 (137.6 mg, 0.75 mmol) in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-chloropurine (192.5 mg, 1.25 mmol) was added. The reaction was maintained at -10 °C, and TLC was monitored. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 1a in 30% yield.

[0097] Example 6:

[0098]

[0099] Synthesis of 1a:

[0100] D-glucose (45 mg, 0.25 mmol) and 1-6 (167.3 mg, 0.75 mmol) were dissolved in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-chloropurine (192.5 mg, 1.25 mmol) was added. The mixture was maintained at -10 °C and monitored by TLC. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 1a in 32% yield.

[0101] Example 7:

[0102]

[0103] Synthesis of 1a:

[0104] D-glucose (45 mg, 0.25 mmol) and 1-7 (188.2 mg, 0.75 mmol) were dissolved in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-chloropurine (192.5 mg, 1.25 mmol) was added. The reaction was maintained at -10 °C, and TLC was monitored. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 1a in 32% yield.

[0105] Example 8:

[0106]

[0107] Synthesis of 1a:

[0108] Dissolve D-glucose (45 mg, 0.25 mmol) and 1-8 (240.8 mg, 0.75 mmol) in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V DioxaneIn a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-chloropurine (192.5 mg, 1.25 mmol) was added. The reaction was maintained at -10 °C, and TLC was monitored. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 1a in 37% yield.

[0109] Example 9:

[0110]

[0111] Synthesis of 1a:

[0112] D-glucose (45 mg, 0.25 mmol) and 1-9 (208.9 mg, 0.75 mmol) were dissolved in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-chloropurine (192.5 mg, 1.25 mmol) was added. The reaction was maintained at -10 °C, and TLC was monitored. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 1a in 50% yield.

[0113] Example 10:

[0114]

[0115] Synthesis of 1a:

[0116] Dissolve D-glucose (45 mg, 0.25 mmol) and 1-10 (165.2 mg, 0.75 mmol) in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-chloropurine (192.5 mg, 1.25 mmol) was added. The reaction was maintained at -10 °C, and TLC was monitored. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 1a in 43% yield.

[0117] Example 11:

[0118]

[0119] Synthesis of 1a:

[0120] D-glucose (45 mg, 0.25 mmol) and 1-11 (183.9 mg, 0.75 mmol) were dissolved in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-chloropurine (192.5 mg, 1.25 mmol) was added. The reaction was maintained at -10 °C, and TLC was monitored. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 1a in 50% yield.

[0121] Example 12:

[0122]

[0123] Synthesis of 1a:

[0124] Dissolve D-glucose (45 mg, 0.25 mmol) and 1-12 (245.0 mg, 0.75 mmol) in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-chloropurine (192.5 mg, 1.25 mmol) was added. The reaction was maintained at -10 °C overnight. The aqueous layer was extracted with DCM, evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give target compound 1a in 40% yield.

[0125] Example 13:

[0126]

[0127] Synthesis of 1a:

[0128] D-glucose (45 mg, 0.25 mmol) and 1-13 (204.7 mg, 0.75 mmol) were dissolved in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-chloropurine (192.5 mg, 1.25 mmol) was added. The reaction was maintained at -10 °C overnight. The aqueous layer was extracted with DCM, evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give target compound 1a in 39% yield.

[0129] Example 14:

[0130]

[0131] Synthesis of 1a:

[0132] Dissolve D-glucose (45 mg, 0.25 mmol) and DMC (127 mg, 0.75 mmol) in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-chloropurine (192.5 mg, 1.25 mmol) was added. The reaction was maintained at -10 °C, and TLC was monitored. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 1a in 47% yield.

[0133] Example 15:

[0134]

[0135] Synthesis of 1b:

[0136] Dissolve D-glucose (45 mg, 0.25 mmol) and 1-1 (228 mg, 0.75 mmol) in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-2-chloropurine (192.5 mg, 1.25 mmol) was added. The reaction was maintained at -10 °C, and TLC was monitored. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 1b in 29% yield.

[0137] Example 16:

[0138]

[0139] Synthesis of 1c:

[0140] Dissolve D-glucose (45 mg, 0.25 mmol) and 1-1 (228 mg, 0.75 mmol) in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V DioxaneIn a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-methoxypurine (187.5 mg, 1.25 mmol) was added. The mixture was maintained at -10 °C and monitored by TLC. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 1c in 46% yield.

[0141] Example 17:

[0142]

[0143] 1d synthesis:

[0144] Dissolve D-glucose (45 mg, 0.25 mmol) and 1-1 (228 mg, 0.75 mmol) in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-purine (150.4 mg, 1.25 mmol) was added. The reaction was maintained at -10 °C, and TLC was monitored. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 1d, with a yield of 36%.

[0145] Example 18:

[0146]

[0147] Synthesis of 1e:

[0148] Dissolve D-glucose (45 mg, 0.25 mmol) and 1-1 (228 mg, 0.75 mmol) in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-1-18 (262.5 mg, 1.25 mmol) was added. The reaction was maintained at -10 °C, and TLC was monitored. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 1e in 35% yield.

[0149] Example 19:

[0150]

[0151] 1f synthesis:

[0152] Dissolve D-glucose (45 mg, 0.25 mmol) and 1-1 (228 mg, 0.75 mmol) in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-1-19 (337 mg, 1.25 mmol) was added. The reaction was maintained at -10 °C and monitored by TLC. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 20:1) to give the target compound 1f in 56% yield.

[0153] Example 20:

[0154]

[0155] Synthesis of 1g:

[0156] Dissolve D-glucose (45 mg, 0.25 mmol) and 1-1 (228 mg, 0.75 mmol) in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-bromopurine (248.7 mg, 1.25 mmol) was added. The reaction was maintained at -10 °C, and TLC was monitored. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give 1 g of the target compound, with a yield of 45%.

[0157] Example 21:

[0158]

[0159] Synthesis in 1 hour:

[0160] Dissolve D-glucose (45 mg, 0.25 mmol) and 1-1 (228 mg, 0.75 mmol) in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-methylpurine (167.5 mg, 1.25 mmol) was added. The reaction was maintained at -10 °C, and TLC was monitored. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound in 1 h, with a yield of 48%.

[0161] Example 22:

[0162]

[0163] Synthesis of 2a:

[0164] D-mannose (45 mg, 0.25 mmol) and 1-1 (228 mg, 0.75 mmol) were dissolved in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-chloropurine (192.5 mg, 1.25 mmol) was added. The mixture was maintained at -10 °C and monitored by TLC. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 2a in 40% yield.

[0165] Example 23:

[0166]

[0167] Synthesis of 2b:

[0168] D-mannose (45 mg, 0.25 mmol) and 1-1 (228 mg, 0.75 mmol) were dissolved in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-bromopurine (248.7 mg, 1.25 mmol) was added. The mixture was maintained at -10 °C and monitored by TLC. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 2b in 35% yield.

[0169] Example 24:

[0170]

[0171] Synthesis of 2c:

[0172] D-mannose (45 mg, 0.25 mmol) and 1-1 (228 mg, 0.75 mmol) were dissolved in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-24 (418.8 mg, 1.25 mmol) was added. The mixture was maintained at -10 °C and monitored by TLC. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 20:1) to give the target compound 2c in 31% yield.

[0173] Example 25:

[0174]

[0175] Synthesis of 3a:

[0176] Dissolve D-xylose (38 mg, 0.25 mmol) and 1-1 (228 mg, 0.75 mmol) in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-chloropurine (192.5 mg, 1.25 mmol) was added. The mixture was maintained at -10 °C and monitored by TLC. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 3a in 31% yield.

[0177] Example 26

[0178]

[0179] Synthesis of 4a:

[0180] L-rhamnose (41 mg, 0.25 mmol) and 1-1 (228 mg, 0.75 mmol) were dissolved in a mixture of water and 1,4-dioxane (total 1 ml, V). 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-chloropurine (192.5 mg, 1.25 mmol) was added. The mixture was maintained at -10 °C and monitored by TLC. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 4a in 27% yield.

[0181] Example 27:

[0182]

[0183] Synthesis of 5a:

[0184] Dissolve D-galactose (45 mg, 0.25 mmol) and 1-1 (228 mg, 0.75 mmol) in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V DioxaneIn a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-bromopurine (248.7 mg, 1.25 mmol) was added. The reaction was maintained at -10 °C, and TLC was monitored. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 5a in 26% yield.

[0185] Example 28:

[0186]

[0187] Synthesis of 6a:

[0188] Cellobiose (85.5 mg, 0.25 mmol) and 1-1 (308.2 mg, 0.75 mmol) were dissolved in a mixture of water and 1,4-dioxane (total 1 ml, V). 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-chloropurine (192.5 mg, 1.25 mmol) was added. The mixture was maintained at -10 °C and monitored by TLC. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 8:1) to give the target compound 6a in 29% yield.

[0189] Example 29

[0190]

[0191] Synthesis of 7a:

[0192] Lactose (85.5 mg, 0.25 mmol) and 1-1 (308.2 mg, 0.75 mmol) were dissolved in a mixture of water and 1,4-dioxane (total 1 ml, V). 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-chloropurine (192.5 mg, 1.25 mmol) was added. The mixture was maintained at -10 °C and monitored by TLC. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 8:1) to give the target compound 7a in 30% yield.

[0193] Example 29

[0194]

[0195] Synthesis of 8a:

[0196] N-acetylglucosamine (55 mg, 0.25 mmol) and 1-1 (228 mg, 0.75 mmol) were dissolved in a mixture of water and 1,4-dioxane (total 1 ml, V). 水 V Dioxane In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, p-6-chloropurine (192.5 mg, 1.25 mmol) was added. The reaction was maintained at -10 °C, and TLC was monitored. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 8a in 42% yield.

[0197] Example 31:

[0198]

[0199] Synthesis of 9a:

[0200] Dissolve D-glucose (45 mg, 0.25 mmol) and 1-1 (228 mg, 0.75 mmol) in a mixture of water and tetrahydrofuran (total 1 ml, V 水 V THF In a 1:1 mixture, 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 5 min. Then, n-butylamine (91.2 mg, 1.25 mmol) was added. The reaction was monitored by TLC at -10 °C. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 9a in 36% yield.

[0201] Example 32:

[0202]

[0203] Synthesis of 10a:

[0204] Dissolve D-glucose (45 mg, 0.25 mmol) and 1-1 (228 mg, 0.75 mmol) in a mixture of water and 1,4-dioxane (total 1 ml, V 水 V Dioxane In a mixture of ethyl acetate and methanol (β:α = 1:1), 350 μL of pre-cooled triethylamine was added at -10 °C, and the reaction was maintained at -10 °C for 30 min. Then, p-aniline (116.4 mg, 1.25 mmol) was added. The reaction was monitored by TLC at -10 °C. After the reaction was complete, the reaction mixture was evaporated to dryness, and purified by column chromatography (eluting with ethyl acetate:methanol = 10:1) to give the target compound 10a (β:α = 3:1), with a yield of 78%.

[0205] References:

[0206] [1]Tanaka T,Nagai H,Noguchi M,et al.One-step conversion ofunprotected sugars to b-glycosyl azides using 2-chloroimidazolinium salt inaqueous solution[J].Chemical communications-royal society of chemistry,2009(23):3378;

[0207] [2]Tomonari,Tanaka,Takeshi,et al.Direct Transformation of UnprotectedSugars to Aryl1-Thio-β-glycosides in Aqueous Media Using 2-Chloro-1,3-dimethylimidazolinium Chloride[J].Chemistry Letters,2009,38(5):458-459;

[0208] [3]M.Sc,Sebastian, et al.One-Pot Synthesis of UnprotectedAnomeric Glycosyl Thiols in Water for Glycan Ligation Reactions with HighlyFunctionalized Sugars[J].

[0209] Angewandte Chemie International Edition,2016;[4]Qiu X,FairbanksAJ.Direct Synthesis of para-Nitrophenyl Glycosides from Reducing Sugars inWater[J].Organic Letters,2020,22(6).

Claims

1. A method for synthesizing N-glycosides without protective sugars, characterized in that, Under conditions of -78℃ to 25℃, unprotected glycosyl donors, acceptors, and bases are dissolved in water or a mixture of water and organic solvents, and a accelerator is added to react and obtain the corresponding glycosides. The general reaction formula is as follows: Where: R represents the structure corresponding to the receptor; The glycosyl donors are glucose, mannose, xylose, rhamnose, galactose, cellobiose, lactose, and N-acetylglucosamine. The acceptor is a nitrogen-containing heterocyclic compound, n-butylamine, or aniline; wherein the nitrogen-containing heterocyclic compound is selected from any of the following structures: 、 ， Wherein, R1 can be hydrogen, fluorine, chlorine, bromine, iodine, amino, NHBoc, or N(Boc). 2； R2 can be hydrogen, fluorine, chlorine, bromine, iodine, amino, NHBoc, or N(Boc)2; The base is triethylamine or DIPEA; The accelerator is selected from any one of the following structures: CDMBI、DMC、 、 、 、 、 、 、 、 、 、 、 、 、 、 。 2. The method according to claim 1, characterized in that, The mixed solvent of water and organic solvent is any one of the following: a mixed reagent of water and tetrahydrofuran, a mixed reagent of water and 1,4-dioxane, a mixed reagent of water and acetonitrile, a mixed reagent of water and DMF, a mixed reagent of water and DMSO, or a mixed reagent of water and acetone.

3. The method according to claim 2, characterized in that: V of the reaction solvent 水 V 有机溶剂 The ratio is 1:

1.

4. The method according to claim 1, characterized in that: The molar ratio of the glycosyl donor to the acceptor is 1:1.1 to 1:10; the molar ratio of the glycosyl donor to the promoter is 1:1.5 to 1:5; and the molar ratio of the glycosyl donor to the base is 1:5 to 1:

20.

5. The method according to claim 1, characterized in that: The temperature is -10℃.

Images