A method for highly stereoselective synthesis of Acinetobacter baumannii surface glycoantigen

Abstract

This invention belongs to the field of organic synthesis technology, specifically relating to a method for synthesizing Acinetobacter baumannii surface glycoantigens with high stereoselectivity. By selecting appropriate protecting groups and a suitable synthetic strategy, this invention first uses retrosynthetic analysis to determine the [2+1+2] synthetic strategy for the key pentasaccharides 2-70 and 2-69. Then, by inducing beta-glycosidic bonds through long-range hydrogen bonding of adjacent sugar levulinyl (Lev) groups, the stereoselectivity problem of high steric hindrance and low reactivity of the receptor is solved, achieving optimization of the synthetic conditions and improvement of stereoselectivity for pentasaccharides 2-70 and 2-69. Finally, the synthesis of the pentasaccharides is achieved by removing the levulinyl protecting group. This invention completes the synthesis of the Acinetobacter baumannii ATCC 17961 lipopolysaccharide O-antigen, facilitating the understanding of the influence of sugar sequence and length on antigenicity, and laying the foundation for the development of glycoantigen vaccines against Acinetobacter baumannii.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, and specifically relates to a method for synthesizing Acinetobacter baumannii surface glycoantigen with high stereoselectivity. Background Technology

[0002] Currently, most of the polysaccharides used in clinically available bacterial polysaccharide and glycoconjugate vaccines are extracted and purified from bacterial cell cultures. These polysaccharides are heterogeneous and prone to batch-to-batch variation. In contrast, glycoconjugate vaccines obtained through chemical synthesis exhibit high consistency and better safety. Furthermore, chemical synthesis allows for selection of representative repeat unit frameshifts, alteration of lengths, and improved design of synthetic oligosaccharide targets, all of which contribute to the development of more stable glycoconjugate vaccines.

[0003] The key to oligosaccharide chemical synthesis lies in the stereoselective construction of glycosidic bonds. Common methods for oligosaccharide chemical synthesis include linear synthesis, convergent synthesis, and the increasingly popular one-pot synthesis strategy. The one-pot synthesis strategy allows multiple glycosylation reactions to proceed continuously in one pot by adjusting the activity of the glycosyl donor or acceptor. Compared to traditional linear and convergent synthesis, one-pot synthesis avoids the adjustment of protecting groups and the separation and purification of intermediates between glycosylation reactions, significantly improving synthetic efficiency.

[0004] Stereochemical control is crucial in glycosylation reactions. Neighbor group participation is one of the most common strategies for guiding the stereochemistry of newly formed glycosidic bonds. A typical glycosylation strategy involves attaching a participating group to the C-2 atom near the anodic center of the glycosyl donor. After the donor is activated, the adjacent group helps stabilize the positive charge forming at the anodic site and stereoelectronically guides the formation of the 1,2-trans glycosidic bond.

[0005] For remote participation-assisted strategies, appropriately designed remotely oriented acyl groups from the C-3, C-4, or C-6 positions in the donor can achieve high 1,2-cis selectivity during glycosylation. Remote participation of the levylpropionyl (Lev) group in glycosidic bonding can be used for highly stereoselective synthetic methods. Currently, all examples of remote group participation involve groups on the same sugar ring of the donor activated during glycosylation, and stereoselective participation is not limited to groups within the activated sugar ring.

[0006] Acinetobacter baumannii is an aerobic, Gram-negative bacillus listed by the World Health Organization as a key target for urgently needed novel antimicrobial drugs. It is a common cause of soft tissue and urinary tract infections, sepsis, pneumonia, and meningitis. With the increasing number of multidrug-resistant strains and their global prevalence, vaccines have become an effective means of preventing and controlling Acinetobacter baumannii infection. In exploring solutions to Acinetobacter baumannii infection, capsular polysaccharides, lipopolysaccharides, lipooligosaccharides, and O-glycans have all emerged as potential immune targets for vaccine development.

[0007] Due to their structural specificity and important potential immunomodulatory activity, this invention designs and synthesizes Acinetobacter baumannii ATCC 17961 lipopolysaccharide O-antigens (including tetrasaccharides with different branching, pentasaccharides containing a single repeating unit, and decasaccharides containing two repeating units). These oligosaccharide molecules can be used to screen for immunogenic epitopes and can also be compared with Acinetobacter baumannii ATCC 17978 capsular polysaccharide O-antigens to understand the influence of sugar sequence and length on antigenicity, laying the foundation for the screening of Acinetobacter baumannii-related sugar antigens. Summary of the Invention

[0008] The purpose of this invention is to provide a method for synthesizing surface glycoantigens of Acinetobacter baumannii A. baumannii. ATCC17961 with high stereoselectivity, which can efficiently synthesize pentasaccharides and decasaccharides, providing a raw material basis for the development of glycoconjugated vaccines.

[0009] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0010] This invention first provides a tetrasaccharide compound, comprising the compound shown in Formula I and the compound shown in Formula II, with the following specific structures:

[0011]

[0012] Furthermore, R1 can be TIPS, Bn, or H.

[0013] Furthermore, Ac represents acetyl, Bn represents benzyl, TIPS represents triisopropylsilyl, Bz represents benzoyl, TCA represents trichloroacetic acid, and Cbz represents benzyloxycarbonyl.

[0014] Specifically, the tetrasaccharide compound shown in Formula II is 2-13, 2-42, or 2-43, with the following structural formula:

[0015]

[0016] Secondly, the present invention also provides a pentasaccharide compound, comprising the compound shown in Formula III, with the following specific structure:

[0017]

[0018] Furthermore, R2 is Lev, Bn, or H; R3 is Lev, Bn, or H; R4 is TBS, or

[0019] Furthermore, Bn represents benzyl, Lev represents acetylpropionyl, Ph represents phenyl, TIPS represents triisopropylsilyl, TBS represents tert-butyldimethylsilyl, TCA represents trichloroacetic acid, and Cbz represents benzyloxycarbonyl.

[0020] Specifically, the compounds represented by Formula III are 2-70, 2-22, 2-69, or 2-23, with the following structural formulas:

[0021]

[0022] Furthermore, based on a general inventive concept, this invention also provides a method for synthesizing the pentasaccharide compound of Formula III. This method, through remote hydrogen bonding induction, achieves the construction of glycosidic bonds using the levulinyl (Lev) group of adjacent sugars while simultaneously improving stereoselectivity. Specifically, it includes the following steps:

[0023] 1) Mix the disaccharide donor, trisaccharide acceptor and toluene and co-evaporate to obtain a mixture. Add organic solvent I to the mixture for pre-reaction, then add catalyst I and react at room temperature (20-25℃) until TLC analysis shows that the acceptor has been completely consumed.

[0024] 2) After the reaction, the product was quenched, filtered, and concentrated under reduced pressure to obtain the crude product. The crude product was then purified by gel column chromatography and silica gel column chromatography to obtain the final product.

[0025] Specifically, the disaccharide donor is 2-21, and its structural formula is:

[0026] Specifically, the trisaccharide receptors are 2-72 and 2-49, with the following structural formulas:

[0027] Specifically, the pre-reaction process in step 1) is as follows: after mixing the mixture with organic solvent I, molecular sieves are added, and the mixture is stirred at room temperature for 10 minutes under an inert atmosphere, and then stirred at 0°C for 5 minutes.

[0028] Specifically, the reaction time in step 1) is 2-6 hours, preferably 4 hours.

[0029] Specifically, the inert atmosphere is formed using nitrogen or argon.

[0030] Specifically, the organic solvent I is dichloromethane, toluene, or chloroform, preferably dichloromethane (DCM).

[0031] Specifically, catalyst I is TMSOTf (trimethylsilyl trifluoromethanesulfonate).

[0032] Specifically, the molar ratio of disaccharide donor to trisaccharide acceptor is (1-2):1; preferably 2:1.

[0033] Specifically, the molar ratio of the trisaccharide receptor to catalyst I is (1.6-1.9):1; preferably 1.838:1.

[0034] Specifically, the volume ratio of organic solvent I to catalyst I is (1-1.5):1; preferably 1.2:1.

[0035] Furthermore, based on a general inventive concept, the present invention also provides the application of the said pentasaccharide compound in the synthesis of decasaccharide compounds.

[0036] Specifically, the decasaccharide compounds include compounds shown in Formula IV and Formula V, with the following structures:

[0037]

[0038] Furthermore, R2 can be Lev, Bn, or H; R3 can be Lev, Bn, or H.

[0039] Furthermore, Bn represents benzyl, Lev represents acetylpropionyl, TIPS represents triisopropylsilyl, TCA represents trichloroacetic acid, and Cbz represents benzyloxycarbonyl.

[0040] Specifically, compounds represented by formula V are 2-24 and 2-75, with the following structural formulas:

[0041]

[0042] Furthermore, the present invention also provides a method for synthesizing a decasaccharide compound using the pentasaccharide compound of Formula III, the synthesis method comprising:

[0043] The pentasaccharide acceptor and pentasaccharide donor reacted at 20-25℃ for 2-4 hours under catalytic conditions, quenched, filtered, concentrated, separated and purified to obtain the decasaccharide compound.

[0044] Specifically, the method for synthesizing the decasaccharide compound 2-24 includes the following steps:

[0045] The pentasaccharide acceptor 2-22 and the pentasaccharide donor 2-23 were mixed with organic solvent II and catalyst II under an inert atmosphere and reacted in an oil bath at 20-25°C (preferably 20°C) for 2-4 h (preferably 3.5 h). The mixture was quenched, filtered, and concentrated to obtain a crude product. The crude product was then purified by gel column chromatography and silica gel column chromatography to obtain decasaccharide compound 2-24.

[0046] Specifically, the inert atmosphere is formed using nitrogen or argon.

[0047] Specifically, the organic solvent II is a mixture of DCM and Et2O, wherein the volume ratio of DCM to Et2O is 1:3.

[0048] Specifically, the catalyst II is TBSOTf (tert-butyldimethylsilyltrifluoromethanesulfonate).

[0049] Specifically, the molar ratio of pentasaccharide receptor 2-22 to pentasaccharide donor 2-23 is 1:(1-1.5); preferably 1:1.3.

[0050] Specifically, the molar ratio of pentasaccharide receptor 2-22 to catalyst II is (2-5):1; preferably 5:1.

[0051] Specifically, the volume ratio of organic solvent II to catalyst II is preferably 1000:1.

[0052] Furthermore, the present invention also provides a method for synthesizing compound 2-75 using compound 2-24, comprising the following steps:

[0053] Compound 2-24 was dissolved in dichloromethane, stirred, and then pyridine and acetic acid were added sequentially. A mixture of N₂H₄·H₂O and AcOH was added under ice bath conditions. After reacting at room temperature for 6 hours, the mixture was diluted, acid-washed, washed with salt solution, dried, concentrated, and purified by column chromatography to obtain a foamy solid, 2-75. The ratio of compound 2-24 to the mixture of N₂H₄·H₂O and AcOH was 1000 g: 1 L. The volume ratio of N₂H₄·H₂O to AcOH was 1:1.

[0054] Furthermore, the present invention also provides a method for synthesizing compound 2-5 using compound 2-75, comprising the following steps:

[0055] Compound 2-75 was dissolved in tetrahydrofuran, and tert-butanol, H2O, AcOH, and Pd(OH)2 / C were added. The mixture was ventilated with H2 in an ice bath for 15 min, and then reacted at room temperature for 5 days under H2 conditions at 1 atm. After filtration and concentration under reduced pressure, compound 2-5 was obtained by separation using a Sephadex LH-20 column. The mass ratio of Pd(OH)2 / C to compound 2-75 was 5:1.

[0056] Compared with the prior art, the advantages of the present invention are:

[0057] This invention synthesizes the lipopolysaccharide O-antigen of Acinetobacter baumannii ATCC17961, including tetrasaccharide, pentasaccharide, and decasaccharide molecules, by selecting appropriate protecting groups and using suitable synthetic strategies. First, retrosynthetic analysis was used to determine the [2+1+2] synthetic strategy for the key pentasaccharides 2-70 and 2-69. Then, by inducing the construction of beta-glycosidic bonds through long-range hydrogen bonding of adjacent sugar levulinyl (Lev) groups, the stereoselectivity problem of high steric hindrance and low reactivity of the acceptor was solved, thus optimizing the synthetic conditions and improving the stereoselectivity of pentasaccharides 2-70 and 2-69. Finally, the synthesis of the pentasaccharides was achieved by removing the levulinyl protecting group.

[0058] This invention has completed the synthesis of the lipopolysaccharide O-antigen of Acinetobacter baumannii ATCC 17961, which facilitates comparison with the capsular polysaccharide O-antigen of Acinetobacter baumannii ATCC 17978, and helps to understand the influence of sugar sequence and length on antigenicity, laying the foundation for the development of sugar vaccines against Acinetobacter baumannii. Detailed Implementation

[0059] The technical solution of the present invention will be further described in detail below through specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0060] In the following examples, the abbreviations are: Ac for acetyl, Ac2O for acetic anhydride, AcOH for glacial acetic acid, All for allyl, Bn for benzyl, Bu2SnO for di-n-butyltin oxide, Bz for benzoyl, Cbz for benzyloxycarbonyl, DCM for dichloromethane, DDQ for 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, DIPEA for diisopropylethylamine, DMAP for 4,4-dimethylaminopyridine, DMF for dimethylformamide, DTBMP for 2,6-di-tert-butyl-4-methylpyridine, EDCI for 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, Et for ethyl, and Im for imidazole. i- Pr stands for isopropyl, Me for methyl, MS for molecular sieve, Nap for 2-(bromomethyl)naphthalene, NBS for N-bromosuccinimide, NIS for N-iodosuccinimide, PE for petroleum ether, EA for ethyl acetate, Ph for phenyl, PiVOH for trimethylacetic acid, PMB for methoxybenzyl, PMBCl for 4-methoxybenzyl chloride, PTFAI for N-phenyltrifluoroacetyl, PTFAICl for N-phenyltrifluoroacetyl chloride, PPY for 4-pyrrolidinylpyridine, and Py for pyridine. tBu is tert-butyl, TBAB is tetrabutylammonium bromide, TBAI is tetrabutylammonium iodide, TBAN is tetrabutylammonium nitrate, TBAF is tetrabutylammonium fluoride, TBDPS is tert-butyldiphenylsilyl, TBDPSCl is diphenyltert-butylchlorosilane, TEMPO is 2,2,6,6-tetramethylpiperidine oxide, BAIB is bis(acetoxy)iodobenzene, TBS is tert-butyldimethylsilyl, TBSCl is dimethyltert-butylchlorosilane, and TCA is trichloroacetic acid. Tf stands for trifluoromethanesulfonate, TIPS stands for triisopropylsilyl, TIPSCl stands for triisopropylchlorosilane, TEA stands for triethylamine, TFA stands for trifluoroacetic acid, THF stands for tetrahydrofuran, TMS stands for trimethylsilyl, TMSOTf stands for trimethylsilyl trifluoromethanesulfonate, TBSOTf stands for tert-butyldimethylsilyltrifluoromethanesulfonate, Tol stands for toluene, Ts stands for p-toluenesulfonyl, TsOH stands for p-toluenesulfonic acid, TCCA stands for trichloroisocyanuric acid, and Lev stands for acetylpropionyl.

[0061] In the following examples, peracetylglucose, D-glucose, and D-glucosamine hydrochloride are conventional commercially available products.

[0062] Example 1: Synthesis of tetrasaccharides, pentasaccharides, and decasaccharides containing diaminoglucuronic acid structure, and optimization of pentasaccharide synthesis method.

[0063] 1. Retrosynthetic analysis of tetrasaccharides 2-3, pentasaccharides 2-4, and decasaccharides 2-5

[0064] For the synthesis of target compounds 2-3, 2-4, and 2-5, this invention employs a convergent synthesis strategy while also exploring a one-pot synthesis strategy. Retrosynthetic analysis of the decasaccharide 2-5 revealed that it is obtained by deprotecting the fully protected decasaccharide 2-24, which in turn is obtained through regio- and stereoselective glycosylation of the pentasaccharide acceptor 2-22 and the pentasaccharide donor 2-23. The one-step hydrogenation of the pentasaccharide 2-22 yields the target molecule 2-4, which is obtained by [2+1+2] glycosylation of the disaccharide acceptor 2-19, the monosaccharide donor 2-7, and the disaccharide donor 2-21 followed by deprotection of the acetylpropionyl group. The synthesis of the pentasaccharide donor 2-23 also begins with [2+1+2] glycosylation to obtain the potential donor, where the anomeric position of the disaccharide acceptor is protected by orthogonally removable TBS. Subsequently, the trifluoroacetylimine ester donor is generated by removing the TBS protecting group and reacting with N-phenyltrifluoroacetyl chloride. The synthesis of the tetrasaccharide target molecule 2-3 is obtained by [2+2] glycosylation of the disaccharide acceptor 2-14 and the disaccharide donor 2-17. Specifically, the following is included:

[0065] 2. Synthesis of tetrasaccharides 2-3

[0066] 2.1 Synthesis of trisaccharides 2-39

[0067] First, this invention optimizes the reaction conditions to selectively protect the C6-hydroxyl group with Bz: using pyridine as a solvent, compound 2-19 is reacted with 2 equivalents of benzoyl chloride at 30°C to synthesize disaccharide 2-14 with a yield of 88%.

[0068] Then, after obtaining the disaccharide acceptor 2-14, the present invention uses trifluoroacetylimine ester donor 2-40 to obtain the trisaccharide product 2-39 in 94% yield under optimal conditions, with a selectivity of β:α = 4:1. The reaction formula for the synthesis of compound 2-39 is as follows:

[0069]

[0070] 2.2 Synthesis of Tetrasaccharide 2-42

[0071]

[0072] The product prepared by the above steps was a mixture of trisaccharide 2-39 and its α-configuration 2-39a. After removing the Nap protecting group from the mixture using DDQ, the completely separated β-configuration product 2-41 was obtained. The trisaccharide acceptor 2-41 was glycosylated with the monosaccharide donor 2-17 to obtain a mixture of tetrasaccharide 2-13 and its α-configuration 2-13a in 85% yield. Then, the silyl protecting group of the tetrasaccharide mixture was removed using HF·Py to obtain the β-configuration product 2-42 in 82% yield.

[0073] 2.3 Synthesis of Tetrasaccharides 2-3

[0074] After obtaining the tetrasaccharide 2-42, the target molecule 2-3 can be synthesized simply by deprotection. First, compound 2-42 was reacted with a 1M aqueous lithium hydroxide solution, and then the intermediate product was hydrogenated under normal pressure for 5 days using Pd(OH)2 / C catalysis, finally yielding the target molecule 2-3 in a high yield.

[0075] The proportions of raw materials and specific steps in the synthesis of tetrasaccharides 2-3 are as follows:

[0076] Compound S13

[0077]

[0078] Compound S12 (1.81 g, 5 mmol) was dissolved in 40 mL of toluene. In a solution dried by MS (to remove water), dibutyltin oxide (2.49 mg, 10 mmol, 2 eq) was added at room temperature. The mixture was refluxed in an oil bath at 120 °C for 6 hours and allowed to cool naturally for 20 minutes. Tetrabutylammonium bromide (1.61 g, 5 mmol, 1 eq) and 4-methoxybenzyl chloride (1.7 mL, 12.5 mmol, 2.5 eq) were added rapidly, and the mixture was heated in an oil bath at 115 °C, maintaining a gentle boil. The mixture was stirred for 5 hours, and the reaction was quenched with triethylamine. The solvent was removed by concentration under reduced pressure, and the mixture was separated by column chromatography (petroleum ether: ethyl acetate 8:1-1:1) to give a white solid S13 (2.03 g, 3.35 mmol, 67%).

[0079] Compound S12 was prepared using the method described in the literature (Zhang Q, Gimeno A, Santana D, Wang Z, Valdés-Balbin Y, Rodríguez-Noda LM, Hansen T, Kong L, Shen M, Overkleeft HS, Vérez-Bencomo V, van der Marel GA, Jiménez-Barbero J, Chiodo F, Codée JDC. Synthetic, Zwitterionic Sp1 Oligosaccharides Adopt a Helical Structure Crucial for Antibody Interaction. ACS Cent Sci. 2019 Aug28;5(8):1407-1416.).

[0080] Compound S14

[0081]

[0082] Under nitrogen protection, compound S13 (1.87 g, 3.1 mmol) was dissolved in 18 mL of pyridine. 4-Dimethylaminopyridine (76 mg, 0.6 mmol, 0.2 eq) was added at room temperature, and the mixture was stirred for 5 minutes. Acetic anhydride (0.43 mL, 4.6 mmol, 1.5 eq) was then added, and the reaction was stirred at room temperature. TLC monitoring showed that the reactants were exhausted. The mixture was diluted with ethyl acetate and transferred out, washed twice with 1N HCl solution, once each with saturated NaHCO3 solution and saturated brine, and then dried over anhydrous Na2SO4. The solution was filtered and concentrated under reduced pressure. Column chromatography (petroleum ether:ethyl acetate 8:1-2:1) yielded a white solid S14 (1.84 g, 2.85 mmol, 92%).

[0083] Compound S16

[0084]

[0085] Compound S14 (1.94 g, 3 mmol) was dissolved in 22 mL of a mixed solvent of acetone and water (10:1 v / v). NBS (1.6 g, 9 mmol, 3 eq) was added in two portions over an ice-water bath. The mixture was slowly brought to room temperature and stirred for 1 hour. TLC was used to monitor the depletion of the reactants. The reaction was quenched by adding saturated sodium thiosulfate solution. The mixture was diluted with DCM and transferred out. The solution was washed successively with water, saturated NaHCO3 solution, and saturated brine. The solution was dried over anhydrous Na2SO4, filtered, and concentrated under reduced pressure. Column chromatography (petroleum ether:ethyl acetate 5:1–1:1) yielded colorless syrup S15 (1.52 g, 2.76 mmol, 92%). Compound S15 (1.05 g, 1.9 mmol) was dissolved in 12 mL of acetone, potassium carbonate (320 mg, 2.3 mmol, 1.2 eq) was added, and the mixture was stirred at room temperature for 10 min. PTFAI (0.46 mL, 2.8 mmol, 1.5 eq) was added, and the mixture was reacted at room temperature for 5 h. Triethylamine was added, the mixture was filtered, concentrated under reduced pressure, and separated by column chromatography (petroleum ether: ethyl acetate 16:1-5:1) to obtain colorless syrup S16 (1.24 g, 1.71 mmol, 90%, α:β = 1.1:1).

[0086] Compound S17

[0087]

[0088] Trifluoroacetylimine ester donor S16 (100 mg, 0.14 mmol, 1 eq) and acceptor S21 (63 mg, 0.19 mmol, 1.4 eq) were dissolved in 2 mL of DCM ( In MS drying and dehydration, newly activated [product / material] is added. MS (200 mg), under nitrogen protection, stirred at room temperature for 30 min, the reaction was placed at -60 °C, TMSOTf (4 μL, 0.02 mmol, 0.15 eq) was added, the temperature was gradually raised to room temperature and stirred for 2 hours, the reaction was quenched by adding triethylamine, filtered, concentrated under reduced pressure, and separated by column chromatography (petroleum ether: ethyl acetate 12:1-3:1) to obtain a mixture of colorless syrups S17 and S17b (117 mg, 98%, α:β = 1:6.5).

[0089] The receptor S21 was prepared using the method described in the literature (Noti C, de Paz JL, Polito L, et al. Preparation and use of microarrays containing synthetic heparin oligosaccharides for therapid analysis of heparin–protein interactions[J]. Chemistry–A European Journal, 2006, 12(34): 8664-8686.).

[0090] Compound S8

[0091]

[0092] Compound S17 (270 mg, 0.31 mmol) was dissolved in 3 mL of a mixed solvent of dichloromethane and methanol (2:1), and sodium methoxide (4 mg, 0.08 mmol, 0.25 eq) was added. The mixture was reacted at room temperature for 48 hours, and the pH was adjusted to about 7 with acidic resin (continuously monitored with pH test paper). The mixture was filtered, concentrated under reduced pressure, and separated by column chromatography (petroleum ether: ethyl acetate 5:1-2:1) to obtain colorless syrup S8 (246 mg, 0.3 mmol, 97%).

[0093] Compound S23

[0094]

[0095] Peracetylglucose olefin (12 g, 44 mmol) was dissolved in a mixture of dichloromethane and methanol (20 mL: 40 mL), and potassium carbonate (3 g, 22 mmol, 0.5 eq) was added. The mixture was reacted at room temperature for 4 hours, filtered, and concentrated under reduced pressure to obtain crude product S22. Crude product S22 was dissolved in 40 mL of LDM, and imidazole (11.98 g, 176 mmol, 4 eq) was added at room temperature. Dimethyl tert-butylchlorosilane (14.59 g, 96.8 mmol, 2.2 eq) was added under an ice-water bath. The mixture was transferred to room temperature and reacted overnight. The mixture was diluted with ethyl acetate and washed three times with water, once each with saturated NaHCO3 solution and saturated brine. The mixture was dried over anhydrous Na2SO4, filtered, concentrated under reduced pressure, and separated by column chromatography (petroleum ether: ethyl acetate 50:1-20:1) to obtain colorless syrup S23 (14.84 g, 39.6 mmol, 90%).

[0096] Compound S25

[0097]

[0098] Compound S23 (9 g, 24 mmol) was dissolved in 100 mL of tetrahydrofuran. The reaction system was placed in an ice-water bath, and sodium hydride (1.92 g, 48 mmol, 2 eq) was added in portions. The mixture was stirred for 20 min, and benzyl bromide (4 mL, 33.6 mmol, 1.4 eq) was slowly added. The mixture was gradually heated to room temperature and reacted overnight. TLC showed that the starting material was exhausted. Methanol was added dropwise to quench the reaction, and the mixture was filtered, concentrated under reduced pressure, and separated by column chromatography (petroleum ether: ethyl acetate 80:1) to obtain colorless syrup S24 (9.15 g, 19.68 mmol, 82%). Compound S24 (5.4 g, 11.6 mmol) was dissolved in 35 mL of tetrahydrofuran, and TBAF (6.6 g, 23.2 mmol, 2 eq) was added. The mixture was reacted at room temperature for 3 hours. When the starting material was exhausted by TLC, the mixture was concentrated under reduced pressure and separated by column chromatography (petroleum ether: ethyl acetate 5:1-1:1) to give a white solid S25 (2.74 g, 10.44 mmol, 90%).

[0099] Compound S27

[0100]

[0101] Compound S25 (8.3 g, 35.1 mmol) was dissolved in 330 mL of DMF, and imidazole (3.59 g, 52.7 mmol, 1.5 eq) was added. Diphenyl tert-butylchlorosilane (10 mL, 38.6 mmol, 1.1 eq) was added under an ice-water bath. The mixture was transferred to room temperature and reacted for 24 hours. TLC showed that the starting material was exhausted. The mixture was diluted with ethyl acetate and transferred out. It was washed three times with water, once each with saturated NaHCO3 solution and saturated brine, dried over anhydrous Na2SO4, filtered, and concentrated under reduced pressure to obtain crude product S26. The crude product was dissolved in a mixed solvent of DCM:Py (120 mL: 60 mL), and 4-dimethylaminopyridine (855 mg, 7 mmol, 0.2 eq) and acetic anhydride (5 mL, 52.6 mmol, 1.5 eq) were added. The mixture was stirred at room temperature, and the reaction mixture was monitored by TLC until the reactants were exhausted. The mixture was diluted with dichloromethane and transferred out, washed twice with 1 N HCl solution, once with saturated NaHCO3 solution, and once with saturated brine. The solution was dried over anhydrous Na2SO4. The mixture was filtered and concentrated under reduced pressure. Column chromatography (petroleum ether:ethyl acetate 30:1-20:1) was used to obtain colorless syrup S27 (15.6 g, 30.18 mmol, 86%).

[0102] Compound S35

[0103]

[0104] Compound S27 (12 g, 23.2 mmol) was dissolved in 250 mL of dichloromethane. Tetrabutylammonium nitrate (14.13 g, 46.4 mmol, 2 eq) and 2,6-di-tert-butyl-4-methylpyridine (9.53 g, 46.4 mmol, 2 eq) were added at room temperature under nitrogen protection. Trifluoromethanesulfonic anhydride (7.8 mL, 46.4 mmol, 2 eq) was added at -70 °C, and the reaction was carried out at -70 °C for 30 min. The dichloromethane was diluted and transferred out, washed with 1 M HCl solution, washed with saturated brine, dried over anhydrous Na2SO4, filtered, concentrated under reduced pressure, and the salt formed in the reaction system was crystallized out with glacial ethyl acetate. The solution was filtered, evaporated to dryness, and separated by column chromatography (petroleum ether: ethyl acetate 20:1-16:1) to obtain colorless syrup S34 (9.6 g, 17.17 mmol, 74%). Compound S34 (3.1 g, 5.5 mmol) was dissolved in 30 mL of dichloromethane, and 4-pyrrolylpyridine (163 mg, 1.1 mmol, 0.2 eq) and trimethylsilane azide (0.87 mL, 6.6 mmol, 1.2 eq) were added. The reaction was carried out at room temperature for 30 min. TLC showed that the starting material was exhausted. Trimethylacetic acid (337 mg, 3.3 mmol, 0.6 eq) and allyl alcohol (1.75 mL, 11 mmol, 2 eq) were added to the reaction system. The system was sealed and reacted in an oil bath at 35 °C for 48 hours. The mixture was concentrated under reduced pressure and separated by column chromatography (petroleum ether: ethyl acetate 30:1-20:1) to obtain colorless syrup S35 (2.25 g, 3.74 mmol, 68%).

[0105] Compound S37

[0106]

[0107] Compound S35 (770 mg, 1.3 mmol) was dissolved in a mixed solvent of tetrahydrofuran:water (15 mL:1.5 mL). Zinc powder (1.7 g, 26 mmol, 20 eq) and copper sulfate (207 mg, 1.3 mmol, 1 eq) were added. Hydrochloric acid (0.68 mL, 13 mmol, 10 eq) was slowly added. The mixture was stirred at room temperature. TLC analysis showed that the starting material was exhausted. Saturated sodium bicarbonate solution was added to neutralize the hydrochloric acid. The mixture was filtered, and the water was evaporated to dryness by azeotropic distillation with toluene to obtain the crude product. The crude product was dissolved in 15 mL of tetrahydrofuran (… (Smoothed by MS), triethylamine (1.4 mL, 10.4 mmol, 8 eq) and trichloroacetyl chloride (0.6 mL, 5.2 mmol, 4 eq) were added, and the mixture was reacted at room temperature for 4 h. After filtration, the mixture was concentrated under reduced pressure and separated by column chromatography (petroleum ether: ethyl acetate 16:1-10:1) to give colorless syrup S36 (640 mg, 0.78 mmol, 60%). Compound S36 (1.43 g, 1.7 mmol) was dissolved in 5 mL of tetrahydrofuran, and tetrabutylammonium fluoride (444 mg, 1.7 mmol, 1 eq) was added. The mixture was reacted at room temperature for 10 h. When the starting material was exhausted by TLC, the mixture was directly concentrated under reduced pressure and separated by column chromatography (petroleum ether: ethyl acetate 5:1-1:1) to give white foamy solid S37 (0.9 g, 1.5 mmol, 88%).

[0108] Compound S33

[0109]

[0110] Compound S37 (1.04 g, 1.7 mmol) was dissolved in a mixed solvent of dichloromethane:water:tert-butanol (2:1:1, 20 mL). TEMPO oxidant (53 mg, 0.34 mmol, 0.2 eq) and BAIB (1.1 g, 3.4 mmol, 2 eq) were added under ice-water bath conditions. The mixture was then transferred to room temperature and reacted overnight. TLC analysis showed that the starting material was exhausted. The reaction was quenched with saturated sodium thiosulfate solution, diluted with dichloromethane, washed with water, and back-extracted from the aqueous phase with dichloromethane. The organic phases were combined, washed with saturated brine, dried over anhydrous Na2SO4, filtered, and concentrated under reduced pressure to obtain the crude product S38. The crude product S38 was dissolved in 10 mL of DMF, and potassium bicarbonate (1.02 g, 10.2 mmol, 6 eq) and benzyl bromide (0.6 mL, 5.1 mmol, 3 eq) were added. The mixture was stirred at room temperature for 18 h. The mixture was diluted with ethyl acetate and transferred out. It was washed three times with water, once each with saturated NaHCO3 solution and saturated brine, and dried over anhydrous Na2SO4. The mixture was filtered, concentrated under reduced pressure, and separated by column chromatography (petroleum ether: ethyl acetate 12:1-8:1) to give a white solid S33 (0.84 g, 1.19 mmol, 70%).

[0111] Compound S7

[0112]

[0113] Compound S33 (0.4 g, 0.57 mmol) was dissolved in 18 mL of a mixed solvent of methanol and dichloromethane in a volume ratio of 2:1. Palladium dichloride (25 mg, 0.14 mmol, 0.25 eq) was added, and the mixture was reacted at 35 °C for 3 h. The mixture was filtered through silica gel, concentrated under reduced pressure, and separated by column chromatography (petroleum ether: ethyl acetate 5:1-1:1) to give a white waxy solid S39 (300 mg, 0.45 mmol, 80%). Compound S39 (300 mg, 0.45 mmol) was dissolved in 4 mL of acetone, and cesium carbonate (176 mg, 0.54 mmol, 1.2 eq) was added. The mixture was stirred at room temperature for 10 min, and PTFAI (0.11 mL, 0.68 mmol, 1.5 eq) was added. The mixture was reacted at room temperature for 5 h, and triethylamine was added. The mixture was filtered, concentrated under reduced pressure, and separated by column chromatography (petroleum ether: ethyl acetate 12:1-8:1) to obtain colorless syrup S7 (305 mg, 0.36 mmol, 81%).

[0114] Compound S75

[0115]

[0116] Donor S7 (104 mg, 0.12 mmol, 1.5 eq) and acceptor S8 (68 mg, 0.083 mmol, 1 eq) were mixed, azeotropically twice with toluene, evaporated to dryness, and dissolved in 2 mL LCM. Add to MS drying and dehydration (x2) MS (200 mg), under nitrogen protection, stirred at -40 °C for 10 min, TBSOTf (4 μL, 0.017 mmol, 0.2 eq) was added, and the reaction was carried out at -40 °C for 2 h. Triethylamine was added to quench the reaction, and the mixture was filtered, concentrated under reduced pressure, and separated by rapid column chromatography (petroleum ether: ethyl acetate 8:1-2:1) to obtain colorless and transparent syrup S75 (106 mg, 0.072 mmol, 87%).

[0117] Compound 2-19

[0118]

[0119] Compound S75 (180 mg, 0.12 mmol, 1 eq) was dissolved in 5 mL of dichloromethane. TFA (0.25 mL) was added under an ice-water bath, and the reaction was gradually brought to room temperature. The reaction mixture was monitored by TLC until the starting material was exhausted. The reaction mixture was then poured into an ice-cold saturated sodium bicarbonate solution and extracted twice with dichloromethane. The organic phases were combined, washed with saturated brine, dried over anhydrous Na2SO4, filtered, concentrated under reduced pressure, and separated by column chromatography (petroleum ether: ethyl acetate 5:1-1:1) to obtain colorless syrup 2-19 (138 mg, 0.11 mmol, 94%).

[0120] Compound 2-14

[0121]

[0122] Compound 2-19 (555 mg, 0.453 mmol) was dissolved in 14 mL of dry pyridine under nitrogen protection. B2Cl (0.11 mL, 0.906 mmol, 2 eq) was added, and the mixture was reacted in an oil bath at 30 °C. After 0.5 h, TCL was used to detect the complete reaction of the starting material. The mixture was diluted with ethyl acetate, washed with H2O and saturated NaCl solution, dried over anhydrous Na2SO4, concentrated, and then purified by dry loading and column chromatography (petroleum ether:ethyl acetate = 10:1 → 2:1) to obtain a foamy solid 2-14 (533 mg, 0.401 mmol, 88%).

[0123] Compound 2-40

[0124]

[0125] Compound 2-12 (400 mg, 0.533 mmol) was dissolved in 4 mL of acetone, 1 mL of H2O was added, and the mixture was placed at 0 °C. NaHCO3 (224 mg, 2.66 mmol, 5 eq) and TCCA (130 mg, 0.559 mmol, 1.05 eq) were added alternately. After 2 h, the reaction was confirmed by TCL to be complete. The reaction was quenched with saturated Na2S2O3 solution, concentrated, dissolved and diluted with dichloromethane, washed with H2O and saturated NaCl solution, dried with anhydrous Na2SO4, concentrated, mixed with dry sample, and purified by column chromatography to obtain 298 mg of the intermediate free of glucosinolates. The intermediate was dissolved in 6 mL of acetone, and Cs2CO3 (226 mg, 0.693 mmol, 1.3 eq) was added. PTFAI (0.11 mL, 0.693 mmol, 1.3 eq) was added under ice bath conditions. The reaction was carried out at room temperature. After 2 h, Et3N was added, filtered, concentrated, and dry-mixed. The mixture was then purified by column chromatography (petroleum ether: ethyl acetate = 20:1 → 10:1) to obtain a pale yellow foamy solid 2-40 (304 mg, 0.373 mmol, 70%).

[0126] Compound 2-12 was prepared using the method described in the literature (Hui Liu, Zhi-Fen Liang, Han-Jian Liu, Jin-Xi Liao, Li-Jun Zhong, Yuan-Hong Tu, Qing-Ju Zhang, Bin Xiong, and Jian-Song Sun, Journal of the American Chemical Society 2023 145(6), 3682-3695.).

[0127] Compound 2-39

[0128]

[0129] The acceptor 2-14 (41 mg, 0.0308 mmol) and the donor 2-40 (50 mg, 0.0616 mmol, 2 eq) were weighed into a reaction flask, azeotropically treated three times with toluene, and pumped for 2 hours. Then, activated [the substance] was added. MS, nitrogen purging 3 times, 2 mL of dry DCM was injected into the system, placed at 0℃, stirred for 10 min, and then TBSOTf (1.4 uL, 0.00616 mmol, 0.2 eq) was injected. After 4 h, TCL detection showed that the acceptor reaction was complete, Et3N was added to quench, filtered, concentrated, dry-mixed, and separated by column chromatography (toluene:ethyl acetate = 50:1 → 10:1) to obtain a mixture of foamy solids 2-39 and 2-39a (57 mg, 0.0291 mmol, 94%, β / α = 4:1).

[0130] Compound 2-41

[0131]

[0132] A mixture of compounds 2-39 and 2-39a (446 mg, 0.228 mmol) was dissolved in 8 mL of dichloromethane. 1.6 mL of buffer solution was added, and DDQ (207 mg, 0.912 mmol, 4 eq) was added in small amounts several times at 0 °C. The temperature was gradually increased to 10 °C, and the reaction was quenched with saturated Na2S2O3 solution after 4.5 h. The mixture was filtered, washed twice with H2O and once with saturated NaCl solution, dried over anhydrous Na2SO4, concentrated, mixed dry, and separated by column chromatography (petroleum ether:ethyl acetate = 10:1 → 2:1) to obtain a foamy solid 2-41 (219 mg, 0.121 mmol, 53%).

[0133] Compound 2-17

[0134]

[0135] Compound S44 (5.9 g, 13.09 mmol) was dissolved in 60 mL of dichloromethane, and DMAP (0.64 g, 5.24 mmol, 0.4 eq) and triethylamine (7.3 mL, 52.36 mmol, 4 eq) were added. Under nitrogen protection, B2Cl (3.1 mL, 26.18 mmol, 2 eq) was slowly added under ice-water bath. The mixture was stirred for 4 h, concentrated under reduced pressure, and separated by column chromatography (petroleum ether: ethyl acetate 10:1-5:1) to give a white solid S76 (5.66 g, 10.21 mmol, 78%). Compound S76 (1.28 g, 2.3 mmol) was placed in a 50 mL round-bottom flask, and boranetetrahydrofuran solution (14 mL, 14 mmol, 6 eq) was added. The mixture was stirred in an ice-water bath for 10 min, and copper trifluoromethanesulfonate (42 mg, 0.12 mmol, 0.05 eq) was added. The mixture was gradually brought to room temperature and stirred overnight. The reaction was quenched dropwise with methanol, filtered, concentrated under reduced pressure, and separated by column chromatography (petroleum ether: ethyl acetate 12:1-5:1) to give a white solid S-77 (1.2 g, 2.16 mmol, 94%).

[0136] Compound S44 was prepared using the method described in the literature (Shie CR, Tzeng ZH, Kulkarni SS, et al. Cu(OTf)2 as an Efficient and Dual-Purpose Catalyst in the Regioselective Reductive Ring Opening of Benzylidene Acetals[J]. Angewandte Chemie International Edition, 2005, 44(11): 1665-1668.).

[0137]

[0138] Compound S77 (5.35 g, 9.61 mmol) was dissolved in 5.5 mL of DMF, and imidazole (0.98 g, 14.42 mmol, 1.5 eq) and DMAP (0.12 g, 0.96 mmol, 0.1 eq) were added. TIPSCl (2.5 mL, 11.68 mmol, 1.2 eq) was added under ice-water bath, and the mixture was transferred to room temperature and reacted for 3 h. The mixture was diluted with ethyl acetate and transferred out. It was washed three times with water, once each with saturated NaHCO3 solution and saturated brine, dried over anhydrous Na2SO4, filtered, concentrated under reduced pressure, and separated by column chromatography (petroleum ether: ethyl acetate 100:1-50:1) to obtain colorless syrup S78 (6.28 g, 8.17 mmol, 85%). Compound S78 (6.28 g, 8.18 mmol) was dissolved in 80 mL of a mixed solvent of acetone and water (3:1 volume ratio). TCCA (2 g, 8.59 mmol, 1.05 eq) and NaHCO3 (3.43 g, 40.88 mmol, 5 eq) were added in two portions in an ice-water bath. The reaction was carried out at 0 °C for 1 hour, quenched with saturated sodium thiosulfate solution, diluted with ethyl acetate, and washed successively with water, saturated NaHCO3 solution, and saturated brine. The mixture was dried over anhydrous Na2SO4, filtered, and concentrated under reduced pressure. Column chromatography (petroleum ether:ethyl acetate 20:1–10:1) yielded colorless syrup S79 (4.26 g, 6.46 mmol, 79%). Compound S79 (1 g, 1.61 mmol) was dissolved in 10 mL of acetone, and cesium carbonate (630 mg, 1.93 mmol, 1.2 eq) was added. The mixture was stirred at room temperature for 10 min, and PTFAICl (0.4 mL, 2.41 mmol, 1.5 eq) was added. The mixture was reacted at room temperature for 5 h, and triethylamine was added. The mixture was filtered, concentrated under reduced pressure, and separated by column chromatography (petroleum ether: ethyl acetate 100:1-60:1) to obtain colorless syrup 2-17 (1 g, 1.26 mmol, 78%).

[0139] Compound 2-13

[0140]

[0141] Receptor 2-41 (219 mg, 0.121 mmol) and donor 2-17 (280 mg, 0.354 mmol, 2.9 eq) were weighed into a reaction flask, azeotropically treated three times with toluene, and pumped for 2 hours. Then, activated [reactant / concentrate / etc.] was added. MS, nitrogen purging 3 times, 6 mL of dry DCM was injected into the system, placed at -20℃, stirred for 10 min, and then TfOH (3.5 μL, 0.0396 mmol, 0.33 eq) was injected. After 2 h, TCL detection showed complete acceptor reaction, Et3N was added for quenching, filtered, concentrated, dry-mixed, and separated by column chromatography (petroleum ether:ethyl acetate = 20:1 → 5:1) to obtain a mixture of foamy solids 2-13 and 2-13a (248 mg, 0.103 mmol, 85%, β / α > 10:1). [α] D 20 = +23.9 (c 1.1, CHCl3); 1 H NMR (400MHz, CDCl3) δ8.07–8.00(m,2H),7.95(d,J=6.4Hz,2H),7.84(d,J=8.2Hz,1H),7.56 (t,J=7.4Hz,1H),7.48(t,J=7.4Hz,1H),7.43(d,J=7.8Hz,2H),7.40–7.18(m,29H),7.18–7. 09(m,14H),7.09–7.02(m,4H),6.95(t,J=7.2Hz,1H),6.89(d,J=5.9Hz,1H),5.32(t,J=8.5 Hz,1H),5.21–5.11(m,3H),5.11–4.99(m,3H),4.92(d,J=10.5Hz,1H),4.89–4.81(m,2H),4. 77(d,J=12.5Hz,1H),4.73–4.64(m,3H),4.59(d,J=10.9Hz,2H),4.54(s,1H),4.50–4.41(m ,5H),4.37(d,J=11.6Hz,2H),4.33–4.24(m,2H),4.16(d,J=11.1Hz,1H),4.13–3.97(m,4H), 3.96–3.70(m,9H),3.69–3.63(m,1H),3.54–3.38(m,3H),3.35–3.21(m,1H),3.10(d,J=29. 5Hz,2H),2.89(d,J=11.9Hz,1H),1.44–1.28(m,4H),1.10–1.05(m,2H),1.05–0.94(m,21H). 13C NMR (100MHz, CDCl3) δ167.54,166.03,165.14,163.47,162.58,162.50,156.63,138.67 ,138.01,137.93,137.86,137.75,137.60,137.23,134.96,133.19,133.00,130.11,130 .08,129.86,129.58,129.15,128.74,128.58,128.52,128.49,128.45,128.35,128.32,128.28,128.26,128.23,128.02,128.00,127.96,127.91,127.87,127.80,127.77,127. 72,127.53,127.34,127.21,102.10,101.14,98.83,96.46,92.40,91.74,91.66,82.92,78.65,77.77,77.54,77.26,76.60,76.47,75.84,75.51,75.44,75.29,75.22,74.95,74 .87,74.16,73.81,73.04,72.83,70.07,67.68,67.46,67.15,66.90,64.74,62.23,57.92,57.28,54.63,50.53,50.18,47.12,46.15,29.12,27.92,27.47,23.36,18.06,11.90.

[0142] Compound 2-42

[0143]

[0144] A mixture of compounds 2-13 and 2-13a (248 mg, 0.103 mmol) was dissolved in 3 mL of tetrahydrofuran and 3 mL of pyridine. 0.3 mL of HF·Py (65.9%) was added under ice bath conditions, and the mixture was stirred at room temperature for 24 h. After 24 h, the mixture was diluted with ethyl acetate and poured into a saturated NaHCO3 solution under ice bath conditions. The solution was stirred for 10 min, extracted, washed once with saturated NaCl solution, dried over anhydrous Na2SO4, concentrated, and purified by dry mixing using column chromatography (petroleum ether:ethyl acetate = 10:1 → 2:1) to obtain a foamy solid 2-42 (191 mg, 0.0845 mmol, 82%), [α]D 20 = +12.4 (c 2.3, CHCl3), 1H NMR(400MHz,CDCl3)δ8.02(d,J=7.2Hz,2H),7.95(d,J=7.2Hz,2H),7.85(d,J=8.4Hz,1H),7.55(t,J=7.4Hz,1H),7.47(t,J=7.4Hz,1H),7.41(t,J=7.7Hz,2H),7.39–7.27(m,18H),7.26–7.09(m,27H),7.08–7.05(m,2H),7.02(t,J=7.0Hz,1H),6.94(d,J=6.0Hz,1H),5.35–5.27(m,1H),5.16(d,J=7.3Hz,3H),5.07(t,J=9.5Hz,2H),5.01(d,J=12.1Hz,1H),4.84(dd,J=11.1,3.9Hz,2H),4.81–4.76(m,1H),4.72(t,J=8.8Hz,2H),4.69–4.59(m,4H),4.58(d,J=4.2Hz,1H),4.54(s,1H),4.47(d,J=10.5Hz,1H),4.45–4.34(m,5H),4.34–4.25(m,2H),4.22–4.05(m,3H),3.98(d,J=9.2Hz,1H),3.94–3.80(m,6H),3.79–3.70(m,4H),3.66(dd,J=10.0,3.3Hz,1H),3.62–3.53(m,1H),3.49–3.37(m,2H),3.36–3.22(m,1H),3.18–3.00(m,2H),2.99–2.82(m,1H),1.44–1.28(m,4H),1.13–0.95(m,2H). 13C NMR (100MHz, CDCl3) δ167.59,166.03,165.24,163.31,162.58,162.49,156.67,1 38.69,137.93,137.77,137.73,137.69,137.53,137.18,134.95,133.31,133.01 ,130.11,129.66,129.58,129.27,128.73,128.59,128.53,128.49,128.39,128.36,128.32,128.29,128.10,128.04,128.00,127.94,127.89,127.84,127.77,12 7.64, 127.34, 127.21, 101.94, 101.12, 99.14, 96.53, 92.39, 91.82, 91.76, 82.46, 78.58, 77.46, 77.28, 75.86, 75.54, 75.48, 75.34, 75.31, 75.01, 74.82, 74.72, 7 4.60,74.35,73.92,73.00,72.92,69.40,67.71,67.51,67.17,66.94,64.69,61.63,57.73,57.12,54.58,50.55,50.20,47.12,46.11,29.11,27.85,27.44,23.36.

[0145] Compounds 2-3

[0146]

[0147] Compound 2-42 (69 mg, 0.0305 mmol) was dissolved in 6 mL of tetrahydrofuran and 2 mL of methanol. 0.2 mL of 1 M LiOH aqueous solution was added, and the reaction was carried out at room temperature. After 11 h, acidic resin was added to neutralize the reaction until the reaction was quenched by weak acidity. The mixture was filtered, concentrated under reduced pressure, and purified by dry mixing and column chromatography to obtain an intermediate with the Bz protecting group removed. This intermediate was dissolved in 1 mL of tetrahydrofuran, and 5 mL of tert-butanol, 2 mL of H2O, and 0.05 mL of AcOH were added. 120 mg of Pd(OH)2 / C (20%) was weighed in, and the mixture was ventilated with H2 in an ice bath for 15 min. The reaction was carried out at room temperature for 5 days under 1 atm H2. The mixture was filtered, concentrated under reduced pressure, and purified by Sephadex LH-20 column (CH3OH:H2O = 1:1) to obtain compound 2-3 (23 mg, 0.0259 mmol, 85%). 1H NMR (600MHz, D2O) δ5.03(d,J=8.4Hz,1H),4.88(d,J=3.9Hz,1H),4.63(d,J=8.5Hz,1H),4.51(d,J=7.9Hz,1H),4.39(d,J= 2.5Hz,1H),4.20(d,J=3.1Hz,1H),4.11(dd,J=10.8,8.6Hz,1H),4.04(dd,J=11.0,10.0Hz,1H),3.93–3.84(m,5H),3.84– 3.77(m,4H),3.76–3.68(m,4H),3.64(dd,J=11.8,6.7Hz,1H),3.59(t,J=9.8Hz,1H),3.56–3.52(m,1H),3.48–3.44(m,1H ),3.44–3.39(m,2H),3.34–3.30(m,1H),3.01(t,J=7.6Hz,2H),2.05–1.94(m,9H),1.73–1.63(m,4H),1.50–1.41(m,2H). 13 C NMR(150MHz,D2O)δ175.78,174.67,174.59,104.36,103.62,101.23,98.44,80.23,80.17,76.19,75.69,75.56,75.51,74.66,72.83,7 0.34,69.84,69.37,67.97,67.86,67.21,61.15,60.44,60.16,54.57,53.54,51.49,39.33,28.02,26.41,22.32,22.31,22.12,21.96.

[0148] 3. Synthesis of pentasaccharides 2-4 and decasaccharides 2-5

[0149] 3.1 Synthesis of compounds 2-18, 2-16, and 2-21

[0150] In the synthesis of pentasaccharides 2-4, this invention employs a [3+2] strategy for glycosylation synthesis of pentasaccharides. The synthesis of the monosaccharide donors and disaccharide donors involved is shown below.

[0151]

[0152] Synthesis of compound 2-18: Starting with D-glucose, compound 2-54 was obtained in 60% yield. Then, the benzylidene protecting group was reduced and cleaved using 1M BH3·THF under TMSOTf catalysis to expose the C6-hydroxyl group, yielding compound 2-55 in 95% yield. The exposed two hydroxyl groups were protected with Lev, yielding compound 2-56 almost quantitatively. Finally, its anolyte thioglycoside was hydrolyzed using NBS, followed by reaction with PTFAI to give the trifluoroacetylimine ester donor 2-18.

[0153] Synthesis of compound 2-16: Starting with compound 2-12, the anomeric position of 2-12 was converted to an allyl group, yielding compound 2-63 in 80% yield. Finally, the naphthyl methyl protection was removed using DDQ to obtain the aminogalactose acceptor 2-16.

[0154] Synthesis of compound 2-21: The β-configuration acceptor 2-16 was reacted with glucose donor 2-18 to obtain a single β-configuration disaccharide 2-66 in 89% yield. Subsequently, the anolyl allyl group was removed using palladium chloride, and the substrate was added after stirring with a base and PTFAI for 10 min to prepare the trifluoroacetylimine ester donor 2-21 in a two-step yield of 48%.

[0155] 3.2 Synthesis of pentasaccharides 2-70 and 2-69

[0156] In the synthesis of 2-70 and 2-69, this invention uses TfOH as a promoter to react compound 2-19 or 2-20 with monosaccharide donor 2-7 at -60°C to obtain trisaccharides 2-72 and 2-49 with a single configuration. Further attempts were made to couple 2-72 or 2-49 with 2-21 using a method that efficiently constructs 1,2-trans glycosidic bonds to build β-glycosidic bonds, but the stereoselectivity was low.

[0157] To improve the synthesis efficiency of pentasaccharides (2-70, 2-69) and further achieve the efficient synthesis of the surface glycoantigen (decansaccharide) of Acinetobacter baumannii ATCC 17961, it is necessary to improve the stereoselectivity of [2+3] glycosylation in pentasaccharide synthesis. Since another sugar chain exists at the C4-O- position, stereoselective glycosylation at the C3-OH of galactose is crucial.

[0158] Therefore, this invention employs a method for constructing beta glycosidic bonds through long-range hydrogen bonding induced by levulinyl (Lev) groups of adjacent sugars. This method achieves stereoselective synthesis of [2+3] glycosylation through the participation of adjacent sugar groups induced by Lev long-range hydrogen bonding, solving the stereoselectivity problems of high steric hindrance and low reactivity of the acceptors. Based on this, this invention starts with disaccharides 2-19 and 2-20, which have completed the construction of 1,2-cis glycosidic bonds, to first synthesize 2-72 and 2-49, and then synthesizes pentasaccharide acceptors 2-70 and 2-69. The general reaction formulas for the synthesis of pentasaccharide acceptors 2-70 and 2-69 are as follows:

[0159]

[0160] The disaccharide donor 2-21 has the following structural formula:

[0161] The structural formulas of receptors 2-72 and 2-49 are as follows:

[0162] The optimal reaction conditions were obtained by optimizing the reaction conditions, as shown in Table 1 below:

[0163] Table 1

[0164]

[0165] After optimizing the reaction conditions, the results showed that the glycosylation of disaccharide donor 2-21 with acceptor 2-49 yielded the desired pentasaccharide 2-69 in 85% yield, exhibiting high stereoselectivity (β:α = 4.5:1). Furthermore, coupling disaccharide donor 2-21 with trisaccharide acceptor 2-72 generated the pentasaccharide 2-70 in 81% yield, with good stereoselectivity (β:α = 5:1). The superior stereoselectivity of compound 2-21 in glycosylation is attributed to the protecting group C2',6'-di-O-acetylacetyl (Lev).

[0166] Finally, the general experimental process of stereoselective glycosylation involving the distal Lev protecting group during the synthesis of pentasaccharide receptors 2-70 and 2-69 was determined to be as follows:

[0167] The mixture of donor (2 equiv) and acceptor (1 equiv) was co-evaporated three times with toluene, and then dried with a fresh flame. Molecular sieves and dried DCM (0.023 M) were added sequentially to a round-bottom flask. The mixture was stirred at room temperature for 10 minutes under nitrogen protection, then stirred at 0°C for 5 minutes. TMSOTf (0.2 eq) was added, and the mixture was gradually brought to room temperature until TLC analysis showed complete consumption of the acceptor. The reaction was quenched with a saturated NaHCO3 aqueous solution, filtered under vacuum, and concentrated under reduced pressure. The crude product was first purified by gel column chromatography (DCM:MeOH = 1:1), followed by silica gel column chromatography to obtain the corresponding product.

[0168] Therefore, the optimized synthesis method for compound 2-69 is as follows:

[0169] Following the general experimental procedure for stereoselective glycosylation involving the distal Lev protecting group, the reaction was carried out using donor 2-21 (166 mg, 0.137 mmol), acceptor 2-49 (110 mg, 0.068 mmol), TMSOTf (2.5 μL, 0.037 mmol), and DCM (3 mL). The reaction was carried out in a 10 mL round-bottom flask, gradually heated to room temperature from an ice-water bath for 4 hours. The crude product was first purified by gel column chromatography (DCM:MeOH = 1:1), and then separated and purified by silica gel column chromatography to obtain a white foamy solid 2-69 (152 mg, 85%, α:β = 1:4.5, PE:EA = 3:1, Rf = 0.4).

[0170] The optimized synthesis method for compound 2-70 is as follows:

[0171] Following the general experimental procedure for stereoselective glycosylation involving the distal Lev protecting group, the following reaction was performed using donor 2-21 (243 mg, 0.2 mmol), acceptor 2-72 (180 mg, 0.1 mmol), TMSOTf (3.5 μL, 0.02 mmol), and DCM (4 mL). The reaction was carried out in a 10 mL round-bottom flask, gradually heated to room temperature from an ice-water bath for 4 hours. The crude product was first purified by gel column chromatography (DCM:MeOH = 1:1), and then separated and purified by silica gel column chromatography to obtain a white foamy solid 2-70 (230 mg, 81%, α:β = 1:5, PE:EA = 2.5:1, Rf = 0.25).

[0172] 3.3 Synthesis of pentasaccharides 2-4

[0173] In the synthesis of 2-70 described above, a mixture of two configurations, 2-70 and 2-70a, was obtained. This invention, after removing some protecting groups, yielded a product with a single configuration. Then, two Lev protecting groups on the pentasaccharide were removed using a hydrazine hydrate acetic acid solution, yielding the pentasaccharide acceptor 2-22 in a high yield of 91%. Finally, the pentasaccharide 2-22 was hydrogenated in one step to obtain the target molecule 2-4.

[0174] 3.4 Synthesis of pentasaccharides 2-23

[0175] The pentasaccharide 2-23 was synthesized using a [3+1+1] glycosylation strategy. After the synthesis of 2-69, the TBS protecting group at the anomeric position of compound 2-69 was removed using TBAF, and then reacted with PTFAI to prepare the trifluoroacetylimine ester donor 2-23. The two-step yield was 84%.

[0176] Synthesis of 3.5 decasaccharides 2-5

[0177] With the pentasaccharide acceptor 2-22 and pentasaccharide donor 2-23, the decasaccharide 2-24 was synthesized using a [5+5] strategy. Experiments revealed that the regioselective glycosylation of the [5+5] combination can occur at the C-6 position of the pentasaccharide acceptor. For the construction of the 1,2-cis-glycosidic bond in the decasaccharide synthesis, this invention employs additive control or solvent effects to achieve the synthesis of α-glycosides. After screening the [5+5] glycosylation conditions, a reaction at 20°C was ultimately selected, using TBSOTf as a catalyst, which improved the α-selectivity of the reaction. Furthermore, increasing the temperature significantly improved the reaction yield.

[0178] After obtaining the decasaccharide product 2-24, the two Lev protecting groups on the decasaccharide were removed using a hydrazine hydrate acetic acid solution, separating the two configurations of products 2-75 and 2-76. With compounds 2-22 and 2-75, the target molecule was synthesized via final hydrogenation. Using Pd(OH)₂ / C as a catalyst, hydrogenation was carried out at atmospheric pressure for 5 days, yielding the target molecule 2-5 in 71% yield.

[0179] The proportions of raw materials and specific steps in the synthesis of pentasaccharides 2-4 and decasaccharides 2-5 are as follows:

[0180] Compound 2-55

[0181]

[0182] Compound 2-54 (6.343 g, 13.6 mmol) was dissolved in 64 mL of dry dichloromethane under nitrogen protection. 1 M BH3·THF (27 mL, 27.2 mmol, 2 eq) and TMSOTf (0.25 mL, 1.36 mmol, 0.1 eq) were added under ice bath conditions. The mixture was gradually brought to room temperature. After 4 h, TCL analysis showed complete reaction of the starting material. The reaction was quenched by adding Et3N and MeOH under ice bath conditions. The mixture was concentrated, wet-mounted, and separated by column chromatography (petroleum ether:ethyl acetate = 10:1 → 2:1) to obtain a white solid 2-55 (6.04 g, 12.9 mmol, 95%).

[0183] Compounds 2-54 were prepared using the method described in the literature (Wang, CC., Lee, JC., Luo, SY. et al. Regioselective one-pot protection of carbohydrates. Nature 446, 896–899 (2007).).

[0184] Compound 2-56

[0185]

[0186] Compound 2-55 (4.94 g, 10.6 mmol), EDCI (8.128 g, 42.4 mmol, 4 eq), and DMAP (647 mg, 5.3 mmol, 0.5 eq) were dissolved in 50 mL of dry dichloromethane under nitrogen protection. LevOH (4.3 mL, 42.4 mmol, 4 eq) and DIPEA (7 mL, 42.4 mmol, 4 eq) were added under ice bath conditions. The mixture was gradually brought to room temperature and reacted. After 3.5 h, TCL analysis showed that the reaction was complete. The mixture was diluted with dichloromethane, washed with H2O and saturated NaCl solution, dried over anhydrous Na2SO4, concentrated, and dry-mixed. The mixture was then separated by column chromatography (petroleum ether: ethyl acetate = 10:1 → 2:1) to obtain a white solid 2-56 (6.95 g, 10.5 mmol, 99%).

[0187] Compound 2-18

[0188]

[0189] Compound 2-56 (4.12 g, 6.22 mmol) was dissolved in 40 mL of acetone, and 4 mL of H2O was added. NBS (3.321 g, 18.7 mmol, 3 eq) was added under ice bath conditions. The reaction was carried out at room temperature for 1 h. Then, NBS (2.214 g, 12.4 mmol, 2 eq) was added to continue the reaction until the reactants were completely reacted. The reaction was quenched with saturated Na2S2O3 solution, concentrated, dissolved and diluted with dichloromethane, washed with H2O and saturated NaCl solution, dried over anhydrous Na2SO4, concentrated, mixed with dry sample, and purified by column chromatography to obtain 3.224 g of the intermediate from which the glucosinolates were removed. The intermediate was dissolved in 32 mL of acetone, and Cs2CO3 (2.828 g, 8.68 mmol, 1.4 eq) was added. PTFAI (1.3 mL, 8.68 mmol, 1.4 eq) was added under ice bath conditions. The mixture was reacted at room temperature, and Et3N was added after 2 h. The mixture was filtered, concentrated, and dry-mixed. The mixture was then purified by column chromatography (petroleum ether: ethyl acetate = 10:1 → 3:1) to obtain a yellowish-brown oily liquid 2-18 (3.712 g, 5.10 mmol, 82%).

[0190] Compound 2-63

[0191]

[0192] Under nitrogen protection, compound 2-12 (110 mg, 0.15 mmol, 1 eq) was... MS (500 mg) dissolved in 5 mL DCM ( In MS (drying), after stirring at 0°C for 10 min, allyl alcohol (0.1 mL, 1.46 mmol, 10 eq), NIS (46 mg, 0.2 mmol, 1.4 eq), and trifluoromethanesulfonic acid (8 μL, 0.09 mmol, 0.6 eq) were added. The mixture was stirred at 0°C overnight for 6 h. Triethylamine and saturated sodium thiosulfate solution were added to quench the reaction. The molecular sieve was removed by filtration, the mixture was concentrated under reduced pressure, and separated by column chromatography (petroleum ether: ethyl acetate 16:1-10:1) to obtain colorless syrup 2-63 (73 mg, 0.12 mmol, 80%).

[0193] Compound 2-16

[0194]

[0195] Compound 2-63 (1.902 g, 2.78 mmol) was dissolved in 25.5 mL of dichloromethane, and 2.5 mL of buffer solution was added. DDQ (945 mg, 4.16 mmol, 1.5 eq) was added in small amounts several times under ice bath conditions. The mixture was gradually brought to room temperature and reacted overnight. The reaction was confirmed by TCL to be complete. The reaction was quenched with saturated Na2S2O3 solution, filtered, washed twice with H2O and once with saturated NaCl solution, dried over anhydrous Na2SO4, concentrated, mixed dry, and purified by column chromatography (petroleum ether:ethyl acetate = 10:1 → 4:1) to obtain a foamy solid 2-16 (1.237 g, 2.27 mmol, 82%).

[0196] Compound 2-66

[0197]

[0198] The acceptor 2-16 (327 mg, 0.6 mmol) and the donor 2-18 (660 mg, 0.9 mmol, 1.5 eq) were weighed into a reaction flask, azeotropically treated three times with toluene, and pumped for 2 hours. Then, activated [reactant / concentrate / etc.] was added. MS, nitrogen purging 3 times, 12 mL of dry DCM was injected into the system, placed at -20℃, stirred for 10 min, and then TBSOTf (28 uL, 0.12 mmol, 0.2 eq) was injected. After 3 h, saturated NaHCO3 solution was added to quench the reaction, filtered, concentrated, dry-mixed, and separated by column chromatography (petroleum ether: ethyl acetate = 10:1 → 3:1) to obtain foamy solid 2-66 (578 mg, 0.533 mmol, 89%).

[0199] Compound 2-21

[0200]

[0201] Compound 2-66 (1.194 g, 1.10 mmol) was dissolved in 15 mL of dichloromethane and 45 mL of methanol. PdCl2 (49 mg, 0.275 mmol, 0.25 eq) was added, and the mixture was reacted in an oil bath at 35 °C. After 3 h, the mixture was filtered through diatomaceous earth and silica gel, and then separated by dry column chromatography to obtain 0.937 g of the intermediate. Cs2CO3 (440 mg, 1.35 mmol, 1.2 eq) and Et3N (0.19 mL, 1.35 mmol) were added. 1.2 eq), PTFAI (0.37 mL, 2.44 mmol, 2.2 eq) and 5 mL of acetone were first added to the reaction flask. Under nitrogen protection, the mixture was stirred at room temperature for 5 min. The intermediate was dissolved in 15 mL of acetone and added to the flask under ice bath conditions. The mixture was gradually brought to room temperature and reacted. After 3 h, Et3N was added, filtered, concentrated, and dry-mixed. The mixture was then purified by column chromatography (petroleum ether: ethyl acetate = 15:1 → 4:1) to obtain a foamy solid 2-21 (644 mg, 0.53 mmol, 48%).

[0202] Compounds 2-7

[0203]

[0204] Compound 2-36 (2.07 g, 2.95 mmol) was dissolved in 20 mL of acetone, and 2 mL of H2O was added. NBS (2.102 g, 11.8 mmol, 4 eq) was added under ice bath conditions. The reaction was carried out at room temperature for 2 h. Then, NBS (526 mg, 2.95 mmol, 1 eq) was added to continue the reaction until the reactants were completely reacted. The reaction was quenched with saturated Na2S2O3 solution, concentrated, dissolved and diluted with dichloromethane, washed with H2O and saturated NaCl solution, dried over anhydrous Na2SO4, concentrated, mixed with dry sample, and purified by column chromatography to obtain 1.594 g of the intermediate from which the glucosinolates were removed. The intermediate was dissolved in 16 mL of acetone, and Cs2CO3 (1.443 g, 4.43 mmol, 1.5 eq) was added. PTFAI (0.8 mL, 5.31 mmol, 1.8 eq) was added under ice bath conditions. The mixture was reacted at room temperature, and Et3N was added after 2 h. The mixture was filtered, concentrated, and dry-mixed. The mixture was then purified by column chromatography (petroleum ether: ethyl acetate = 15:1 → 8:1) to give a pale yellow waxy solid 2-7 (1.762 g, 2.30 mmol, 78%).

[0205] Compounds 2-36 were prepared using the method described in the literature (Zhang, Yonglian; Knapp, Spencer. Simplified beta-glycosylation of peptides (Article) [J]. Tetrahedron, 2018, Vol. 74 (23): 2891-2903.).

[0206] Compound 2-72

[0207]

[0208] Receptor 2-19 (958 mg, 0.782 mmol) and donor 2-7 (810 mg, 1.06 mmol, 1.35 eq) were weighed into a reaction flask, azeotropically treated three times with toluene, and pumped for 2 hours. Then, activated [reactant / concentrate / etc.] was added. MS, nitrogen purging 3 times, 48 ​​mL of dry DCM was injected into the system, placed at -60℃, stirred for 10 min, and then TfOH (7 uL, 0.0782 mmol, 0.1 eq) was injected. After 4 h, TCL detection showed that the acceptor reaction was complete, Et3N was added to quench, filtered, concentrated, dry-mixed, and separated by column chromatography (petroleum ether: ethyl acetate = 10:1 → 3:1) to obtain foamy solid 2-72 (1.253 g, 0.695 mmol, 89%).

[0209] Compound 2-70

[0210]

[0211] The acceptor 2-72 (180 mg, 0.1 mmol) and the donor 2-21 (243 mg, 0.2 mmol, 2 eq) were weighed into a reaction flask, azeotropically treated three times with toluene, and pumped for 2 hours. Then, activated [reactant / concentrate / etc.] was added. MS, nitrogen purging 3 times, 4 mL of dry DCM was injected into the system, placed at 0℃, stirred for 10 min, and then TMSOTf (3.5 uL, 0.02 mmol, 0.2 eq) was injected. After 4 h, saturated NaHCO3 solution was added to quench the reaction, filtered, concentrated, and first separated using a gel column (MeOH:DCM = 1:1), followed by dry mixing and column chromatography (petroleum ether:ethyl acetate = 10:1 → 2.5:1) to obtain a mixture of foamy solids 2-70 and 2-70a (230 mg, 0.0813 mmol, 81%, β / α = 5:1). [α]D 20 = +2.2 (c 0.55, CHCl3); 1 H NMR (400MHz, CDCl3) δ8.47(dd,J=15.9,5.6Hz,1H),7.92(d,J=8.1Hz,1H),7.53(d,J=7.9Hz,1H), 7.36(d,J=5.5Hz,4H),7.34–7.29(m,12H),7.28–7.23(m,17H),7.18(s,21H),7.12–7.04(m,5H),6 .96(d,J=9.2Hz,1H),6.86(d,J=6.4Hz,1H),5.31–5.23(m,1H),5.22–5.10(m,4H),5.08–4.99(m, 2H),4.88–4.77(m,4H),4.76–4.70(m,4H),4.69–4.62(m,4H),4.57(d,J=11.0Hz,2H),4.53–4.45( m,5H),4.40(d,J=10.4Hz,5H),4.35–4.18(m,4H),4.09–3.95(m,4H),3.94–3.87(m,4H),3.86–3. 84(m,1H),3.84–3.78(m,5H),3.75–3.67(m,1H),3.64–3.58(m,2H),3.57–3.49(m,3H),3.45(d,J= 9.8Hz,1H),3.42–3.31(m,1H),3.28–3.14(m,2H),3.09–2.83(m,2H),2.72–2.62(m,1H),2.58(t, J=6.2Hz,2H),2.48–2.33(m,3H),2.15(s,5H),2.04(s,3H),1.57–1.39(m,4H),1.25–1.13(m,2H).13 C NMR (100MHz, CDCl3) δ208.18,206.72,172.26,171.58,168.00,163.79,162.64,162.32,161 .90,156.25,139.61,139.12,138.59,138.20,138.04,138.01,137.53,137.38,137.11,136 .67,135.16,129.18,128.61,128.58,128.47,128.34,128.26,128.23,128.11,127.93,127.85,127.83,127.78,127.70,127.62,127.57,127.44,127.32,127.26,101.91,101.46,99. 64,99.23,97.55,92.83,92.52,92.40,91.76,82.32,80.97,79.03,78.37,77.91,77.69,76.32,76.17,75.61,75.29,75.13,75.02,74.88,74.71,74.65,73.76,73.55,73.30,73.09,7 2.77, 69.93, 69.08, 68.47, 67.97, 67.43, 67.22, 62.80, 57.66, 57.08, 55.96, 54.72, 50.60, 50.18, 47.45, 46.41, 37.90, 37.79, 30.04, 29.84, 29.42, 28.15, 27.87, 27.76, 27.40, 23.65.

[0212] Compound 2-22

[0213]

[0214] Compound 2-70 (419 mg, 0.148 mmol) was dissolved in 3.2 mL of dichloromethane. 1.6 mL of pyridine and 1 mL of acetic acid were added sequentially with stirring. 0.15 mL of N2H4·H2O / AcOH (volume ratio 1:1) was added under ice bath conditions. After reacting at room temperature for 5.5 h, the dichloromethane was diluted. The solution was first washed with 1 M hydrochloric acid, then with saturated NaHCO3 solution and NaCl solution. The solution was dried over anhydrous Na2SO4, concentrated, and then separated by column chromatography (petroleum ether:ethyl acetate = 5:1 → 1.5:1) to obtain a foamy solid 2-22 (356 mg, 0.135 mmol, 91%). 1H NMR(400MHz,d6-Acetone)δ8.49(d,J=9.3Hz,1H),8.41(t,J=9.5Hz,1H),8.23(d,J=7.6Hz,1H),8.01(d,J=8.9Hz,1H),7.42(dd,J=11.9,7.4Hz,6H),7.34–7.29(m,20H),7.28–7.24(m,17H),7.23(s,5H),7.21(s,8H),7.20(s,3H),7.10(t,J=7.3Hz,1H),5.56(d,J=8.4Hz,1H),5.19(q,J=12.6Hz,4H),5.03(t,J=10.2Hz,2H),4.93–4.76(m,8H),4.75–4.61(m,6H),4.60–4.50(m,7H),4.46–4.34(m,6H),4.29–4.20(m,3H),4.16(d,J=2.7Hz,1H),4.05(t,J=9.2Hz,3H),4.01–3.93(m,1H),3.92–3.84(m,3H),3.82(d,J=2.5Hz,3H),3.78–3.69(m,4H),3.68–3.59(m,2H),3.58–3.50(m,4H),3.47(dd,J=9.2,3.6Hz,1H),3.42–3.37(m,1H),3.29–3.16(m,2H),3.13–3.03(m,1H),1.60–1.42(m,4H),1.30(s,2H). 13C NMR(100MHz,d6-Acetone)δ163.33,163.25,163.19,162.91,162.84,162.40,162.32,140.58,140. 27,139.80,139.62,139.53,139.50,139.36,138.85,136.46,129.60,129.40,129.29,129.15,129 .12,129.04,129.00,128.96,128.95,128.91,128.89,128.87,128.67,128.64,128.60,128.59,128.49,128.45,128.43,128.33,128.31,128.25,128.21,128.16,128.11,128.03,127.98,127.92,1 05.32,102.38,102.13,102.04,97.36,94.23,94.19,93.85,93.81,93.72,93.68,93.42,93.39,85.40,83.05,79.57,79.34,78.25,77.34,77.10,76.90,76.47,76.19,76.05,75.85,75.61,75.33,7 5.31,75.27,75.23,75.12,74.94,73.90,73.36,73.21,71.71,71.57,70.58,69.93,69.33,68.14,67.69,67.37,62.23,62.11,58.13,56.39,55.75,50.94,47.99,47.00,30.10,28.82,28.29,24.28.

[0215] Compounds 2-4

[0216]

[0217] Compound 2-22 (32 mg, 0.0124 mmol) was dissolved in 1 mL of tetrahydrofuran, and 5 mL of tert-butanol, 2 mL of H2O, and 0.05 mL of AcOH were added. 120 mg of Pd(OH)2 / C (20%) was weighed in, and the mixture was ventilated with H2 in an ice bath for 15 min. The reaction was carried out at room temperature for 5 days under H2 conditions at 1 atm. The mixture was filtered, concentrated under reduced pressure, and separated using a Sephadex LH-20 column (CH3OH:H2O = 1:1) to obtain compound 2-4 (6.7 mg, 0.00614 mmol, 49%). 11H NMR (600 MHz, D2O) δ 8.45 (s, 1H), 5.01 (d, J = 8.4 Hz, 1H), 4.86 (d, J = 3.9 Hz, 1H), 4.61 (d, J = 8.5 Hz, 1H), 4.50 (d, J = 7.9 Hz, 1H), 4.47 (d, J = 8.5 Hz, 1H), 4.36 (d, J = 2.4 Hz, 1H), 4.19 (d, J = 3.1 Hz, 1H), 4.14–4.08 (m, 2H), 4.02 (dd, J = 11.0, 10.0 Hz, 2H), 3.95 (d, J = 11.9 Hz, 1H), 3.92–3.84 (m, 4H), 3.83–3.73 (m, 5H), 3.73–3.67 (m, 4H), 3.66–3.63 (m, 1H), 3.59 (t, J = 9.8 Hz, 1H), 3.54–3.50 (m, 1H), 3.50–3.39 (m, 6H), 3.34–3.30 (m, 1H), 3.02 (t, J = 7.5 Hz, 2H), 2.01 (dd, J = 7.0, 1.5 Hz, 12H), 1.73–1.60 (m, 4H), 1.51–1.41 (m, 2H). 13 13C NMR (150 MHz, D2O) δ 175.55, 174.72, 174.59, 174.57, 174.10, 104.34, 103.63, 101.78, 101.29, 98.00, 80.35, 80.11, 77.38, 76.70, 75.78, 75.69, 75.50, 74.70, 74.10, 72.83, 71.61, 70.48, 69.78, 69.37, 69.31, 67.97, 67.11, 61.22, 60.44, 55.51, 54.64, 53.59, 51.50, 39.38, 27.98, 26.45, 22.48, 22.32, 22.18, 22.15, 21.96.

[0218] Compound S85

[0219]

[0220] Compound S15 (1.1 g, 2 mmol) was dissolved in 10 mL of DMF, and imidazole (272 mg, 4 mmol, 2 eq) and dimethyl tert-butylchlorosilane (452 ​​mg, 3 mmol, 1.5 eq) were added sequentially. Under nitrogen protection, the mixture was stirred overnight at room temperature. The solution was diluted with ethyl acetate and transferred out. The solution was washed three times with water, once each with saturated NaHCO3 solution and saturated brine, and dried over anhydrous Na2SO4. The solution was filtered, concentrated under reduced pressure, and separated by column chromatography (petroleum ether: ethyl acetate 12:1-6:1) to obtain colorless syrup S84 (1.16 g, 1.74 mmol, 87%, β configuration). Compound S84 (250 mg, 0.37 mmol) was dissolved in dichloromethane:methanol (2:1, 3 mL), sodium methoxide (10 mg, 0.18 mmol, 0.5 eq) was added, and the mixture was reacted at room temperature for 5 hours. The pH was adjusted to about 7 with acidic resin (continuous pH monitoring with pH paper), filtered, concentrated under reduced pressure, and separated by column chromatography (petroleum ether:ethyl acetate 10:1-5:1) to obtain colorless syrup S85 (208 mg, 0.33 mmol, 90%).

[0221] Compound S86

[0222]

[0223] Donor S7 (84 mg, 0.1 mmol, 1.5 eq) and acceptor S85 (42 mg, 0.067 mmol, 1 eq) were mixed, azeotropically twice with toluene, evaporated to dryness, and dissolved in 2 mL of DCM. Add to MS drying and dehydration (x2) MS (200 mg), under nitrogen protection, stirred at -40 °C for 10 min, added TBSOTf (3 μL, 0.013 mmol, 0.2 eq), reacted at -40 °C for 2 h, quenched with triethylamine, filtered, concentrated under reduced pressure, and separated by rapid column chromatography (petroleum ether: ethyl acetate 12:1-6:1) to obtain colorless transparent syrup S86 (73 mg, 0.057 mmol, 85%).

[0224] Compound 2-20

[0225]

[0226] Compound S86 (950 mg, 0.75 mmol) was dissolved in 25 mL of DCM, and 5 mL of buffer solution was added. DDQ (0.41 g, 1.8 mmol, 2.4 eq) was added under ice-water bath conditions, and the reaction was gradually brought to room temperature for 5 h. The reaction was quenched with saturated sodium thiosulfate solution, diluted with ethyl acetate, and filtered. The filtrate was washed successively with water, saturated NaHCO3 solution, and saturated brine, dried over anhydrous Na2SO4, filtered, concentrated under reduced pressure, and separated by column chromatography (petroleum ether: ethyl acetate 8:1-2:1) to obtain colorless syrup 2-20 (596 mg, 0.58 mmol, 78%).

[0227] Compound 2-49

[0228]

[0229] Receptor 2-20 (872 mg, 0.847 mmol) and donor 2-7 (973 mg, 1.27 mmol, 1.5 eq) were weighed into a reaction flask, azeotropically treated three times with toluene, and pumped for 2 hours. Then, activated [reactant / concentrate / etc.] was added. MS, nitrogen purging 3 times, 44 mL of dry DCM was injected into the system, placed at -60℃, stirred for 10 min, and then TfOH (7.5 uL, 0.0847 mmol, 0.1 eq) was injected. After 3.5 h, TCL detection showed that the acceptor reaction was complete, Et3N was added to quench, filtered, concentrated, dry-mixed, and separated by column chromatography (petroleum ether: ethyl acetate = 10:1 → 3:1) to obtain foamy solid 2-49 (1.27 g, 0.79 mmol, 93%).

[0230] Compound 2-69

[0231]

[0232] Receptor 2-49 (110 mg, 0.068 mmol) and donor 2-21 (166 mg, 0.137 mmol, 2 eq) were weighed into a reaction flask, azeotropically treated three times with toluene, pumped for 2 hours, and then activated... MS, nitrogen purging 3 times, 3 mL of dry DCM was injected into the system, placed at 0℃, stirred for 10 min, and then TMSOTf (3 μL, 0.014 mmol, 0.2 eq) was injected. After 2.5 h, saturated NaHCO3 solution was added to quench the reaction, filtered, concentrated, and first separated using a gel column (MeOH:DCM = 1:1), followed by dry mixing and column chromatography (petroleum ether:ethyl acetate = 10:1 → 3:1) to obtain a mixture of foamy solids 2-69 and 2-69a (152 mg, 0.0578 mmol, 85%, β / α = 4.8:1). β-configuration product 2-69: [α]D 20=+1.8(c 3.0,CHCl3), 1 H NMR(400MHz,CDCl3)δ8.25(d,J=6.6Hz,1H),7.88(d,J=8.1Hz,1H),7.35–7.30(m,6H),7.30–7.23(m,27H),7.22–7.17(m,10H),7.16(s,5H),7.12–7.06(m,6H),6.91(d,J=8.2Hz,1H),5.30(d,J=8.2Hz,1H),5.19–5.11(m,2H),5.06(d,J=12.2Hz,1H),5.03–4.98(m,1H),4.81(s,1H),4.78(s,2H),4.76(d,J=3.0Hz,2H),4.74–4.71(m,2H),4.71–4.66(m,4H),4.66–4.60(m,2H),4.58(d,J=4.5Hz,1H),4.55(s,1H),4.50(dd,J=14.3,2.0Hz,2H),4.46(d,J=5.6Hz,1H),4.44–4.40(m,2H),4.38(s,2H),4.36–4.31(m,1H),4.19(dd,J=11.9,4.7Hz,1H),4.10–4.02(m,1H),4.00–3.89(m,6H),3.86–3.76(m,6H),3.74–3.66(m,1H),3.62–3.42(m,10H),2.99–2.87(m,1H),2.59–2.48(m,3H),2.41(t,J=6.3Hz,2H),2.38–2.28(m,1H),2.13–2.05(m,4H),2.03(s,3H),0.77(s,9H),0.07(s,3H),0.00(s,3H). 13C NMR (100MHz, CDCl3) δ208.10,206.47,172.20,171.48,167.85,163.88,162.72,162.44,16 1.80,139.48,138.49,138.15,137.98,137.95,137.87,137.85,137.48,137.33,134.98,12 9.13, 128.77, 128.63, 128.55, 128.51, 128.47, 128.46, 128.43, 128.37, 128.24, 128.20, 128.17, 128.08, 127.96, 127.92, 127.84, 127.78, 127.75, 127.72, 127.67, 127.60, 127.55, 12 7.09, 126.97, 101.85, 101.47, 99.40, 98.67, 98.21, 92.65, 92.47, 92.07, 91.54, 82.38, 82.29, 80.27, 80.13, 78.13, 77.82, 77.62, 77.28, 76.20, 75.29, 75.23, 75.18, 75.14, 75.10, 74 .88,74.79,74.67,73.62,73.32,73.25,73.17,72.96,70.29,68.95,68.46,67.65,62.69,57.69,57.35,57.07,54.81,37.81,37.74,30.05,29.78,27.83,25.83,17.98,-3.66,-4.50.

[0233] Compound 2-23

[0234]

[0235] Compound 2-69 (532 mg, 0.202 mmol) was dissolved in 10 mL of tetrahydrofuran, and 1 M TBAF tetrahydrofuran solution (0.61 mL, 0.606 mmol, 3 eq) and AcOH (35 μL, 0.606 mmol, 3 eq) were added. The mixture was reacted in an oil bath at 30 °C for 36 h, then concentrated. The mixture was then dry-mixed and separated by column chromatography (petroleum ether: ethyl acetate = 4:1 → 1:1) to obtain 450 mg of the intermediate. The solid was dissolved in 9 mL of acetone, and Cs2CO3 (105 mg, 0.322 mmol, 1.6 eq) and PTFAI (41 μL, 0.27 mmol, 1.3 eq) were added under ice bath conditions. The mixture was gradually heated to room temperature and reacted. After 3 h, Et3N was added, filtered, concentrated, and mixed with a dry sample. The mixture was then separated by column chromatography (petroleum ether: ethyl acetate = 10:1 → 2.5:1) to obtain a foamy solid 2-23 (453 mg, 0.168 mmol, 84%). 1H NMR(400MHz,d6-Acetone)δ8.49–8.44(m,2H),8.41(d,J=9.4Hz,1H),8.10(d,J=9.3Hz,1H),7.44(d,J=7.2Hz,3H),7.38–7.35(m,4H),7.34–7.32(m,7H),7.32–7.31(m,5H),7.30–7.27(m,10H),7.26(s,8H),7.25–7.22(m,9H),7.21–7.16(m,5H),7.13(t,J=7.4Hz,1H),7.02(t,J=7.4Hz,1H),6.57(d,J=7.7Hz,2H),6.38(s,1H),5.53(d,J=8.4Hz,1H),5.27(d,J=12.5Hz,1H),5.20–5.14(m,2H),5.06(dd,J=9.5,8.1Hz,1H),4.97(d,J=11.4Hz,1H),4.88–4.83(m,3H),4.83–4.80(m,2H),4.79(s,1H),4.78–4.76(m,3H),4.67(t,J=4.7Hz,3H),4.63(d,J=4.5Hz,2H),4.58(d,J=8.4Hz,3H),4.56–4.49(m,2H),4.47–4.43(m,1H),4.42(d,J=3.1Hz,1H),4.38(s,1H),4.35(d,J=1.6Hz,1H),4.33(s,1H),4.32–4.28(m,2H),4.27–4.19(m,2H),4.10(d,J=9.2Hz,2H),4.07–4.02(m,2H),4.02–3.98(m,2H),3.97–3.93(m,1H),3.90–3.86(m,1H),3.85–3.81(m,3H),3.80–3.72(m,3H),3.68(d,J=5.1Hz,1H),3.67–3.63(m,2H),3.59–3.53(m,1H),2.85–2.75(m,3H),2.71–2.65(m,2H),2.56–2.45(m,3H),2.15(s,3H),2.05(s,3H). 13C NMR(100MHz,d6-Acetone)δ206.98,206.37,172.01,171.85,168.36,162.51,162.43,162.04,162.00,161. 97,161.92,161.75,161.67,143.82,139.15,138.80,138.68,138.66,138.62,138.58,138.41,138.38,138. 03,135.63,128.80,128.52,128.50,128.31,128.30,128.27,128.24,128.20,128.18,128.12,128.10,128.04,128.02,127.83,127.75,127.68,127.67,127.65,127.50,127.39,127.35,127.29,127.18,126.91,123. 82,119.34,101.69,101.41,101.24,100.70,94.04,93.26,93.22,92.99,92.95,92.85,92.81,92.45,92.41,82.29,81.94,81.91,79.44,78.54,78.11,77.36,77.06,76.60,75.71,75.33,75.18,74.85,74.67,74.56 ,74.47,74.42,74.26,74.05,73.43,73.38,73.24,73.01,72.48,72.34,69.38,69.08,67.07,62.65,57.17,57.08,56.95,56.86,55.36,55.27,55.00,54.89,54.59,37.67,37.39,29.10,28.89,27.90,27.65.Compounds 2-24

[0236]

[0237] Receptor 2-22 (113 mg, 0.043 mmol, 1 eq) and donor 2-23 (150 mg, 0.0558 mmol, 1.3 eq) were weighed into a sealing tube, and activated [the drug / method] was added. MS, nitrogen purging 3 times, 2 mL of dry DCM / Et2O (1:3, volume ratio) and TBSOTf (2 μL, 0.00859 mmol, 0.2 eq) were added under nitrogen atmosphere, and the mixture was placed in an oil bath at 20 °C for reaction. After 3.5 h, saturated NaHCO3 solution was added to quench the reaction, filtered, concentrated, and first separated by gel column chromatography (MeOH:DCM = 1:1), followed by dry mixing and column chromatography separation (petroleum ether:ethyl acetate = 5:1 → 2:1) to obtain a mixture of foamy solids 2-24 and 2-24b (183 mg, 0.0357 mmol, 83%, β / α = 1:1).

[0238] Compound 2-75

[0239]

[0240] A mixture of compounds 2-24 and 2-24b (120 mg, 0.0234 mmol) was dissolved in 2.6 mL of dichloromethane. 1.3 mL of pyridine and 0.8 mL of acetic acid were added sequentially with stirring. 0.12 mL of N₂H₄·H₂O / AcOH (volume ratio 1:1) was added under ice bath conditions. After reacting at room temperature for 6 h, the dichloromethane was diluted, washed first with 1 M hydrochloric acid, then with saturated NaHCO₃ solution and NaCl solution, dried over anhydrous Na₂SO₄, concentrated, and then separated by column chromatography (petroleum ether:ethyl acetate = 5:1 → 2:1) to obtain a foamy solid 2-75 (55 mg, 0.011 mmol, 48%). [α]D 20 = +20.6 (c 1.1, CHCl3), 1H NMR(600MHz,d6-Acetone)δ8.45–8.35(m,2H),8.18(dd,J=7.7,3.0Hz,1H),8.10(d,J=7.9Hz,1H),7.94(d,J=8.5Hz,1H),7.91(d,J=9.3Hz,1H),7.45–7.39(m,8H),7.34(dd,J=11.2,4.5Hz,14H),7.32–7.28(m,36H),7.28–7.26(m,18H),7.25(d,J=2.5Hz,4H),7.25–7.22(m,14H),7.22–7.19(m,7H),7.18–7.16(m,6H),7.16–7.14(m,2H),7.14–7.10(m,2H),7.09–7.05(m,1H),5.47(d,J=8.4Hz,2H),5.22(dd,J=11.4,4.1Hz,3H),5.14(s,4H),5.11(d,J=8.3Hz,1H),5.07(d,J=3.2Hz,1H),5.04(d,J=11.6Hz,1H),5.01(d,J=11.5Hz,1H),4.91(d,J=11.4Hz,1H),4.88(d,J=2.8Hz,1H),4.86(d,J=5.0Hz,1H),4.85–4.82(m,3H),4.81(s,2H),4.79(d,J=3.2Hz,2H),4.78(d,J=3.5Hz,1H),4.76(d,J=4.9Hz,1H),4.74(d,J=4.4Hz,1H),4.71(d,J=8.8Hz,2H),4.68(s,1H),4.66–4.64(m,2H),4.64(d,J=2.4Hz,2H),4.59(d,J=12.2Hz,1H),4.55(s,3H),4.54–4.53(m,3H),4.52(s,2H),4.51–4.48(m,3H),4.46(d,J=11.8Hz,2H),4.43(s,1H),4.41(s,1H),4.40(s,1H),4.38–4.35(m,2H),4.33–4.26(m,4H),4.26–4.17(m,5H),4.14–4.08(m,5H),4.08–4.02(m,4H),4.08–3.99(m,8H),4.01(d,J=9.9Hz,3H),3.98–3.94(m,5H),3.93–3.87(m,3H),3.86–3.81(m,6H),3.80–3.76(m,4H),3.75–3.69(m,4H),3.65–3.60(m,5H),3.57–3.55(m,2H),3.54–3.49(m,6H),3.48–3.46(m,1H),3.45–3.39(m,3H),3.37–3.34(m,1H),3.29–3.19(m,2H),3.11–3.01(m,1H),1.59–1.50(m,4H),1.36–1.32(m,2H). 13C NMR(150MHz,d6-Acetone)δ209.79,209.75,169.09,169.03,163.34,163.32,163.27,163.24,163.20,163.16,162.92,162.86,162.84,162.79,162.52,162.45,162.35,162.28,157.13,156.53,140.56,140.42,140.24,140.03,139.76,139.63,139.52,139.48,139.45,139.43,139.32,139.26,139.18,138.86,138.81,138.40,138.16,136.47,136.45,129.67,129.41,129.36,129.30,129.27,129.23,129.15,129.11,129.09,129.08,129.03,129.02,128.97,128.93,128.92,128.88,128.86,128.65,128.63,128.61,128.57,128.54,128.51,128.48,128.45,128.40,128.34,128.30,128.24,128.22,128.20,128.17,128.14,128.10,128.04,128.00,127.97,127.94,127.90,127.82,106.00,105.32,102.50,102.26,102.15,101.88,101.67,98.01,97.36,97.20,94.39,94.36,94.21,94.17,93.84,93.80,93.77,93.61,93.58,93.42,93.38,93.26,93.23,85.57,85.53,85.31,85.27,82.97,82.87,82.84,80.16,79.58,79.31,79.08,79.05,78.18,78.14,77.92,77.88,77.78,77.48,77.05,76.95,76.48,76.20,76.13,76.10,75.99,75.95,75.87,75.83,75.76,75.72,75.55,75.48,75.42,75.34,75.28,75.26,75.21,75.19,75.09,74.86,73.90,73.88,73.71,73.44,73.29,73.20,73.09,73.06,72.39,72.28,71.73,71.53,71.28,71.04,70.71,70.41,69.94,69.91,69.67,69.26,68.14,68.00,67.65,67.54,67.35,66.75,62.20,62.07,61.98,61.85,58.4 5,58.36,58.25,58.19,58.14,58.10,57.97,57.10,56.92,56.80,56.58,56.52,56.49,55.93,55.79,55.69,55.46,55.43,50.97,50.76,48.03,47.07,30.36,28.87,28.26,24.28.

[0241] Compounds 2-5

[0242]

[0243] Compound 2-75 (30 mg, 0.00608 mmol) was dissolved in 1 mL of tetrahydrofuran, and 5 mL of tert-butanol, 2 mL of H2O, and 0.05 mL of AcOH were added. 150 mg of Pd(OH)2 / C (20%) was weighed in, and the mixture was ventilated with H2 in an ice bath for 15 min. The reaction was carried out at room temperature for 5 days under H2 conditions at 1 atm. The mixture was filtered, concentrated under reduced pressure, and separated using a Sephadex LH-20 column (CH3OH:H2O = 1:1) to obtain compound 2-5 (9 mg, 0.00432 mmol, 71%). 1H NMR(600MHz,D2O)δ4.94(d,J=8.4Hz,1H),4.91(d,J=8.4Hz,1H),4.83(d,J=3.8Hz,1H),4.77(d,J=3.9Hz,1H),4.52(d,J=8.5Hz,2H),4.47(d,J=7.8Hz,1H),4.43(d,J=7.8Hz,1H),4.41–4.37(m,2H),4.28(d,J=9.7Hz,2H),4.11(d,J=2.5Hz,2H),4.07–4.05(m,2H),4.03(d,J=1.4Hz,1H),4.02(d,J=4.0Hz,1H),3.98(d,J=12.0Hz,1H),3.95(d,J=6.2Hz,1H),3.93(s,1H),3.91(d,J=2.1Hz,1H),3.88(s,1H),3.86(s,1H),3.84(s,1H),3.81(s,1H),3.79(s,3H),3.77(d,J=2.9Hz,2H),3.76(d,J=3.5Hz,1H),3.75–3.73(m,2H),3.71(d,J=2.8Hz,1H),3.69(s,2H),3.68–3.66(m,4H),3.64(d,J=5.1Hz,2H),3.63–3.61(m,4H),3.60(d,J=4.4Hz,2H),3.57–3.54(m,3H),3.51(s,2H),3.50(s,1H),3.48(s,1H),3.46–3.42(m,2H),3.38(s,2H),3.37(s,4H),3.33(d,J=7.7Hz,2H),3.25–3.22(m,2H),2.93(t,J=7.5Hz,2H),1.95–1.90(m,24H),1.64–1.58(m,4H),1.40–1.34(m,2H). 13C NMR(150MHz,D2O)δ175.57,175.55,174.73,174.68,174.62,174.57,174.22,174.10,104.69,104.31,103.84,103.61,101.84,101.79, 101.31,101.26,98.01,80.56,80.32,80.15,80.11,77.39,76.72,76.67,75.79,75.67,75.59,75.49,74.80,74.63,74.19,74.11,74.01 ,72.87,72.80,71.61,71.43,70.50,70.38,69.78,69.53,69.38,69.32,68.90,68.03,67.92,67.32,67.16,67.11,64.69,61.69,61.48,61.22,61.14,60.55,60.44,55.60,55.52,54.65,53.58,51.55,51.42,39.39,28.00,26.46,22.50,22.33,22.25,22.19,22.16,21.97.

[0244] In summary, this invention has successfully synthesized the lipopolysaccharide O-antigen of Acinetobacter baumannii ATCC 17961, including tetrasaccharide, pentasaccharide, and decasaccharide molecules, by selecting appropriate protective groups and using suitable synthetic strategies.

[0245] For the synthesis of highly branched tetrasaccharides 2-3, pentasaccharides 2-4, and decasaccharides 2-5, this invention employs a method that first achieves the challenging linkage between diaminoglucuronic acid and the C4-hydroxyl group of galactose. Subsequently, by flexibly adjusting the donor volume and protecting group, stereoselective construction of the densely branched galactose C-3 glycosidic bond is achieved. Experiments revealed that using the disaccharide donor 2-21 containing a Lev protecting group in reaction with the trisaccharide acceptor yields the desired glycoside product with excellent yield and stereoselectivity. Simultaneously, a one-pot synthesis of the potential pentasaccharide acceptor and donor is realized. Utilizing the solvent effect, a [5+5] glycosylation reaction is finally performed, yielding the decasaccharide molecule in excellent yield.

Claims

1. A method for synthesizing a pentasaccharide compound, characterized in that, The pentasaccharide compound is compound 2-4, with the following structure: ; The method for synthesizing compounds 2-4 includes the following steps: 1) Mix the disaccharide donor, trisaccharide acceptor and toluene and co-evaporate to obtain a mixture. Add organic solvent I to the mixture for pre-reaction, then add catalyst I and react at room temperature until the acceptor is completely consumed. 2) After the reaction, the mixture was quenched, filtered, and concentrated under reduced pressure to obtain the crude product. The crude product was then purified by gel column chromatography and silica gel column chromatography to obtain compound 2-70. Compound 2-70 was deprotected by acetylpropionyl to obtain compound 2-22. 3) Compound 2-22 was dissolved in 1 mL of tetrahydrofuran, 5 mL of tert-butanol, 2 mL of H2O and 0.05 mL of AcOH were added, 120 mg of Pd(OH)2 / C was weighed in, H2 was exchanged in an ice bath for 15 min, and the reaction was carried out at room temperature for 5 days under H2 at 1 atm. The mixture was filtered, concentrated under reduced pressure, and separated by Sephadex LH-20 column to obtain compound 2-4. The structural formula of compound 2-70 is: ; The disaccharide donor is 2-21, and its structural formula is: ; The trisaccharide receptor is 2-72, and its structural formula is: ; Compound 2-22 has the following structural formula: ; The pre-reaction process in step 1) is as follows: after mixing the mixture with organic solvent I, molecular sieve is added, and the mixture is stirred at room temperature for 10 minutes under an inert atmosphere, and then stirred at 0°C for 5 minutes. The reaction time in step 1) is 2-6 hours; The inert atmosphere is formed using nitrogen or argon. The organic solvent I is dichloromethane, toluene, or chloroform; the catalyst I is TMSOTf. The molar ratio of disaccharide donor to trisaccharide acceptor is (1-2):1; the molar ratio of trisaccharide acceptor to catalyst I is (1.6-1.9):1; and the volume ratio of organic solvent I to catalyst I is (1-1.5):

1.

2. A method for synthesizing decasaccharide compounds using compounds 2-22 as described in claim 1, characterized in that, The decasaccharide compound is compound 2-5, with the following structural formula: ; The method for synthesizing compounds 2-5 includes the following steps: The pentasaccharide acceptor 2-22 and pentasaccharide donor 2-23 were mixed with organic solvent II and catalyst II under an inert atmosphere and reacted in an oil bath at 20-25°C for 2-4 hours. The mixture was then quenched, filtered, and concentrated to obtain the crude product. The crude product was then purified by gel column chromatography and silica gel column chromatography to obtain the decasaccharide compound 2-24. The inert atmosphere is formed using nitrogen or argon. The organic solvent II is a mixture of DCM and Et2O, wherein the volume ratio of DCM to Et2O is 1:3; The catalyst II is TBSOTf; The molar ratio of pentagasaccharide receptor 2-22 to pentagasaccharide donor 2-23 is 1:(1-1.5). The molar ratio of pentagasaccharide receptor 2-22 to catalyst II is (2-5):1; The volume ratio of organic solvent II to catalyst II is 1000:1; Compound 2-24 was dissolved in dichloromethane, stirred, and pyridine and acetic acid were added sequentially. A mixture of N2H4·H2O and AcOH was added under ice bath conditions. After reacting at room temperature for 6 h, the mixture was diluted, acid-washed, washed with salt solution, dried, concentrated, and purified by column chromatography to obtain foamy solid 2-75. The ratio of compound 2-24 to the mixture of N2H4·H2O and AcOH is 1000g:1L; The volume ratio of N2H4·H2O to AcOH is 1:1; Compound 2-75 was dissolved in tetrahydrofuran, and tert-butanol, H2O, AcOH, and Pd(OH)2 / C were added. The mixture was ventilated with H2 in an ice bath for 15 min, and then reacted at room temperature for 5 days in an H2 environment at 1 atm. The mixture was filtered, concentrated under reduced pressure, and separated by a Sephadex LH-20 column to obtain compound 2-5. The mass ratio of Pd(OH)2 / C to compound 2-75 is 5:

1. The structural formula of compound 2-24 is: ; The compound 2-75 has the following structural formula: ; Compound 2-23 has the following structural formula: ; The method for synthesizing compounds 2-23 includes the following steps: 1) Mix the disaccharide donor, trisaccharide acceptor and toluene and co-evaporate to obtain a mixture. Add organic solvent I to the mixture for pre-reaction, then add catalyst I and react at room temperature until the acceptor is completely consumed. 2) After the reaction, the product was quenched, filtered, and concentrated under reduced pressure to obtain a crude product. The crude product was then purified by gel column chromatography and silica gel column chromatography to obtain compound 2-69. After removing the TBS protecting group from compound 2-69, compound 2-23 was obtained. The structural formula of compound 2-69 is: ; The disaccharide donor is 2-21, and its structural formula is: ; The trisaccharide receptor is 2-49, and its structural formula is: ; The pre-reaction process in step 1) is as follows: after mixing the mixture with organic solvent I, molecular sieve is added, and the mixture is stirred at room temperature for 10 minutes under an inert atmosphere, and then stirred at 0°C for 5 minutes. The reaction time in step 1) is 2-6 hours; The inert atmosphere is formed using nitrogen or argon. The organic solvent I is dichloromethane, toluene, or chloroform; the catalyst I is TMSOTf. The molar ratio of disaccharide donor to trisaccharide acceptor is (1-2):1; the molar ratio of trisaccharide acceptor to catalyst I is (1.6-1.9):1; and the volume ratio of organic solvent I to catalyst I is (1-1.5):1.

Images