Synthesis of hexacyl-4 '-monophosphoryl ester A and intermediate thereof

Abstract

The invention relates to synthesis of hexacyl-4 '-monophosphoryl ester A and an intermediate thereof. The key difficulty in chemical synthesis of HMLA is construction of chiral glycosidic bonds, currently commonly used glycosidic bond construction methods Schmidt glycosylation and Koenigs-Knorr glycosylation have limitations, and thioglycoside glycosylation commonly used in glycosylation is not reported in synthesis of HMLA, which indicates that thioglycoside glycosylation and thioglycoside donor structures are closely related to reaction conditions. By accurately designing the structure of the thioglycoside donor and optimizing the reaction conditions, the synthesis process development of the HMLA and the thioglycoside donor intermediate thereof is completed, and the HMLA and thioglycoside donor intermediate thereof are successfully applied to large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of pharmaceutical technology, specifically relating to a method for synthesizing hexaacyl-4'-monophosphoryl ester A (HMLA) and its intermediates. Background Technology

[0002] Lipopolysaccharide (LPS) is a complex cell surface component unique to Gram-negative bacteria, mainly composed of three parts: an outermost oxygen-linked polysaccharide antigen, a middle core polysaccharide, and an innermost hydrophobic lipid A (lipid A). These components are potent stimulants of the host defense system and can be used as adjuvants to vaccine antigens and inducers of nonspecific anti-infection ability in animal models. However, the strong pyrogenicity and lethal toxicity of LPS limit its medical applications. Therefore, researchers are dedicated to designing and synthesizing lipid A analogs with simplified structures, lower toxicity, and superior bioactivity.

[0003] In 1954, Westphal and Lüderitz of the Max Planck Institute for Immunobiology in Germany developed the hot phenol-water method (Westphal method), which was the first to efficiently extract LPS from Gram-negative bacteria (such as Salmonella), laying the foundation for subsequent research on lipid A (Angew. Chem. Int. Ed. 1954, 66, 407-417).

[0004] In 1985, Mayer and Galanos of the Max Planck Institute in Germany improved the LPS purification technique (Eur J Biochem., 1985, 148, 1-5.) and systematically studied the relationship between the structure and toxicity of lipid A, finding that reducing the number of phosphate groups could reduce toxicity. They were the first to isolate lipid A from rough strains such as Salmonella Minnesota R595 and attempted chemical modifications (such as dephosphorylation).

[0005] In 1987, Ribi's team first obtained monophospholipid A (MPLA) from Salmonella LPS through mild acid hydrolysis combined with subsequent alkaline phosphatase treatment, and demonstrated that it retained adjuvant activity but with significantly reduced toxicity. This work directly promoted the clinical application of MPLA (J Biol Response Mod., 1987, 6, 99-107).

[0006] In the 1990s, with GlaxoSmithKline's (GSK) promotion of QS-21, MPLA, in conjunction with QS-21, became an important component of the AS01B adjuvant system.

[0007] In the 21st century, a series of preclinical animal model studies confirmed that the AS01B adjuvant system has a strong CD8+ T cell and antibody response. After 2010, the malaria vaccine Mosquirix and the recombinant shingles vaccine Shingrix, which use the AS01B adjuvant system, were successively approved for marketing.

[0008] Currently, other vaccines, including HIV and tuberculosis vaccines, have entered the clinical research stage, and the AS01B adjuvant system using lipid monophosphate A (MPLA) is ushering in a golden age of rapid development.

[0009] There are currently three main methods for obtaining MPLA: the first method is to extract it from the Salmonella Minnesota R595 mutant strain and then obtain it through chemical treatment; the second method is to construct an E. coli mutant that synthesizes hexaacylated MPLA or pentaacylated MPLA (P-MPLA) by integrating / or deleting key genes related to lipid A biosynthesis and modification in chromosomes; and the third method is to obtain it through total chemical synthesis.

[0010] The preparation of MPLA through chemical synthesis has significant advantages: On the one hand, the main drawback of naturally derived lipid A is the difficulty in obtaining sufficient quantities of material with pharmaceutical-grade purity, stable activity, and reproducibility. The difficulties lie in the following two aspects: (1) the inherent variability of the assembly steps in the biosynthesis of lipid A molecules; and (2) the loss of fatty acid chains on the lipid A backbone during processing and purification. Therefore, from the perspective of production process, it is difficult to ensure batch-to-batch consistency of the mixture components, and component differences will significantly affect its bioactivity and toxicity. On the other hand, modifying Escherichia coli through genetic engineering also faces a series of problems. The high complexity of biosynthesis, the increased metabolic burden on E. coli, and the accumulation of byproducts may lead to a decrease in cell survival rate and limited yield. At the same time, the heterogeneity of biosynthesis will also lead to difficulties in subsequent separation and purification, reducing batch stability and activity.

[0011] Naturally derived monophospholipid A can contain multiple homologous forms with 3 to 6 acyl chains. Hexaacylated monophospholipid A is considered the optimal structure for TLR4 activation (Monophosphoryl Lipid A as an Adjuvant. InVaccine Design: The Subunit and Adjuvant Approach; Powell, MF, Newman, MJ, Eds.; Plenum: New York, 1995; pp 495-524.). In 1999, Johnson's group compared the activity and toxicity of a mixture of MPLA isolated from Salmonella and purified by alkalization with that of a single hexaacylated monophospholipid A structure in MPLA. The results showed that hexaacylated monophospholipid A (HMLA) containing 14+14, 14+12, and 14+16 nucleotides in MPLA was the main contributor to MPLA activity and had lower toxicity than the MPLA mixture.

[0012] Currently, vaccines using naturally derived MPLA as an adjuvant have been launched successively, resulting in significant market growth. In the future, with further market development, the production of naturally derived MPLA will inevitably face immense pressure, and the market will place higher demands on the efficacy and safety of adjuvants. Therefore, obtaining a single-structure HMLA through chemical synthesis is inevitably a better choice to address both production capacity and safety concerns. Developing a simple, stable, and controllable synthetic method capable of large-scale production is therefore increasingly urgent.

[0013] The hexaacyl-4'-monophosphoryl ester A protected by this invention is a hexaacylated structure of MPLA. Its acyl side chain lengths are 14+14, 14+12, and 14+16, respectively, which are attached to the 3', 2', and 2 positions of the sugar fragment. Its structure contains four different acyl side chains, making it the most complex MPLA compound in terms of structure, optimal combination of activity and toxicity, and the most difficult to synthesize. Currently, only a few papers have reported related synthetic studies.

[0014] .

[0015] In 1998, David A. Johnson's research group (J. Carbohydrate Chemistry., 1998, 17, 1421-1426.) started from the thioglycoside intermediate formula III-1, and obtained intermediate formula III-3 through amino protection and hydroxyl esterification. After removing the benzene protecting group from formula III-3, the 6-hydroxyl group was protected with ethyl 1,1-dimethyl-2,2,2-trichloroformate. Then, the 4-hydroxyl group was converted into phenyl phosphate formula III-6. The thioglycoside was then prepared into chloroglycoside formula III-7, which underwent Koenigs-Knorr glycosylation with a glycoside acceptor to generate disaccharide intermediate formula III-8. Then, the Troc protecting groups on the nitrogen and oxygen atoms were removed in one step to obtain formula III-9. The amino group was selectively amidated with the carboxylic acid chain, and then hydrogenation was used to remove all protecting groups to obtain HMLA.

[0016] Theoretically, the compound of formula III-6 used by David A. Johnson's research group could directly synthesize the disaccharide fragment of formula III-8 through glucosinolate glycosylation and interaction with the acceptor. This would reduce the number of synthetic steps and save on production costs. However, the authors did not use the thioglycoside intermediate of formula III-6 and the acceptor for direct glucosinolate glycosylation. Instead, they chose to convert the prepared glucosinolate donor into a chloroglycoside of formula III-7 before performing Koenigs-Knorr glycosylation. This also reflects that direct glucosinolate glycosylation places more stringent requirements on the substrate structure, reaction reagents, reaction conditions, and catalysts, requiring more precise control. This also poses higher demands for the subsequent use of glucosinolate glycosylation to construct the disaccharide structure of HMLA. Therefore, selecting a suitable glucosinolate donor and corresponding reaction conditions for glucosinolate glycosylation is of great significance and urgent need.

[0017] .

[0018] In 2001, Jiang Zi-Hua Justin's group (WO0136433A2) at Lakehead University, Canada, used the classic Schmidt glycosylation method to synthesize the disaccharide fragment IV-3 from Schmidt donor IV-1 and acceptor IV-2. After removing the Troc protecting group, the 2' amino group underwent amidation, followed by selective reduction of the benzylidene, and further phosphorylation to obtain the fully protected intermediate IV-7. Finally, all protecting groups were removed in one step to obtain hexaacyl monophosphate lipid A (HMLA). Schmidt glycosylation uses highly reactive trichloroacetylimine ester as a donor, which readily interacts with trace amounts of water, alcohols, and other nucleophiles under acidic conditions, leading to substrate inactivation and the generation of byproducts. It is also prone to decomposition and rearrangement during column purification and concentration, yielding various byproducts. The biggest challenge faced by Jiang's group in constructing disaccharide glycosidic bonds using the Schmidt glycosylation method is the difficulty in synthesizing the unstable trichloroacetylimine ester intermediate, formula IV-1, in large quantities, which hinders large-scale production. Therefore, developing a synthetic method other than Schmidt glycosylation is also extremely important.

[0019] .

[0020] In 2025, Chengdu Maikekang, in collaboration with Li Tiehai's research group at the Shanghai Institute of Materia Medica, developed a synthesis method for hexaacyl-4'-monophosphoryl ester A (HMLA) (Angew. Chem. Int. Ed. 2025, 64, e202418948). Starting from intermediate formula V-1 protected by naphthyl groups at positions 4 and 6, a modified Schmidt donor formula V-2 was formed through multiple transformations. Subsequently, it was glycosylated with acceptor formula V-3 to obtain disaccharide intermediate formula V-4. After further transformations, various protecting groups such as -Allyl, -Alloc, -Nap, and -TBS were removed to obtain HMLA. This report still uses a modified Schmidt glycosylation strategy to construct β-glycosidic bonds, which also faces the challenge of large-scale production. Secondly, the variety of protecting groups used in the substrate leads to an increase in substrate synthesis steps and the number of protecting group removal steps, which will significantly increase production costs in industrial and GMP production processes.

[0021] Based on a review of the literature on the synthesis of HMLA, it can be seen that the commonly used methods for synthesizing this compound are still the common Schmidt glycosylation and Koenigs-Knorr glycosylation methods. However, both of these methods also face significant limitations. Industrial-scale mass production typically focuses on three important aspects: firstly, simple and easy-to-operate processes; secondly, stable and easily stored intermediates; and thirdly, cost control advantages. Both Schmidt glycosylation and Koenigs-Knorr glycosylation have their respective limitations. Summary of the Invention

[0022] This invention provides a more suitable synthetic method for the industrial production of hexaacyl-4'-monophosphoryl ester A. Addressing the limitations of current HMLA synthesis methods in industrial applications, such as lengthy steps, poor substrate stability, numerous byproducts, and difficulty in large-scale production, this invention achieves a simple and efficient construction of the disaccharide structure of HMLA by precisely controlling and configuring the protecting group of thioglycoside intermediate I and optimizing the glycosylation conditions of the thioglycoside substrate. The multiple ester bonds in HMLA are highly unstable under acidic or alkaline conditions. All protecting groups are removed through a two-step hydrogenation process under mild neutral conditions. This synthetic strategy results in stable intermediates, fewer side reactions, a simple process, low cost, and scalability for mass production.

[0023] The present invention is achieved through the following technical solution.

[0024] The first objective of this invention is to provide an intermediate I for the synthesis of hexaacyl-4'-monophosphoryl ester A, with the following structural formula:

[0025] ;

[0026] Wherein, R1 is selected from C1-6 alkyl groups and phenyl groups optionally substituted with C1-6 alkyl groups; Bn represents benzyl, and Troc represents trichloroethoxyformyl, i.e. Examples of R1 include, but are not limited to, methyl, ethyl, propyl, phenyl, p-methylphenyl, o-methylphenyl, or m-methylphenyl.

[0027] A second objective of this invention is to provide a method for synthesizing the aforementioned intermediate I, comprising the following steps:

[0028] Step a: In the presence of a reducing agent and an acidic agent, the exposed 4-hydroxyl group at the benzylmethylene protecting group at positions 4 and 6 in Formula I-1 is selectively reduced to obtain Formula I-2;

[0029] ;

[0030] Step b: In the reaction solvent, in the presence of a phosphorylating agent and a basic agent, the exposed hydroxyl group at the 4-position of Formula I-2 is phosphorylated to obtain thioglycoside donor intermediate I;

[0031] ;

[0032] The definitions of R1, Bn, and Troc are as described above.

[0033] Further, in step a, the selected reducing agent is one or more of the following: trimethylsilane (Me3SiH), triethylsilane (Et3SiH), triphenylsilane (Ph3SiH), borane (BH3), boranetetrahydrofuran (BH3·THF), diphenylborane chloride (Ph2BCl), and sodium cyanoborohydride (NaBH3CN), preferably triethylsilane (Et3SiH); the equivalent amount of Et3SiH is in the range of 2.0-8.0 eq, preferably 5.0 eq; the acidic agent is selected from trichloride... One or more of aluminum (AlCl3), hydrochloric acid (HCl), trifluoromethanesulfonic acid (TfOH), boron trifluoride ether (BF3·OEt), silver trifluoromethanesulfonate (AgOTf), trimethylsilyl trifluoromethanesulfonate (TMSOTf), triethylsilyl trifluoromethanesulfonate (TESOTf) or tert-butyldimethylsilyl trifluoromethanesulfonate (TBSOTf), preferably BF3·OEt2; the equivalent of BF3·OEt2 used is 0.5-3.0 eq of Formula I-1, preferably 1-1.15 eq.

[0034] Further, in step a, the reaction solvent is one or more of dichloromethane (DCM), tetrahydrofuran (THF), dioxane, diethyl ether (Et2O) or toluene (PhMe), preferably dichloromethane (DCM).

[0035] Furthermore, in step a, the reaction temperature range is 10-40℃, preferably 20-25℃;

[0036] Further, in step b, the reaction solvent is one or more of dichloromethane (DCM), dichloroethane (DCE), or ethyl acetate (EA), with dichloromethane (DCM) being preferred.

[0037] Further, in step b, the phosphorylating agent is diphenyl chlorophosphate, and the reaction equivalent range is 1.0-4.0 eq of Formula I-2, preferably 1.5 eq;

[0038] Further, in step b, the alkaline reagent is selected from one or more of triethylamine, diisopropylamine or diisopropylethylamine, preferably triethylamine; the amount used is 0.5-10 eq of formula I-2, preferably 1.5 eq.

[0039] Furthermore, in step b, the reaction temperature is 5-50℃, preferably 10-25℃.

[0040] A third object of the present invention is to provide a method for preparing compound II-2 using the above intermediate I, comprising the following steps:

[0041] Step c: Compound II-1 and intermediate I react with a glycosylation reagent to obtain compound II-2.

[0042] ;

[0043] Further, in step c, the mass ratio of the compound of formula II-1 to intermediate I is 1:1.0-1.5, preferably 1:1.1-1.2.

[0044] Further, in step c, the reaction solvent is selected from one or more of dichloromethane (DCM), dichloroethane (DME), diethyl ether (Et2O) or toluene (PhMe), preferably dichloromethane (DCM).

[0045] Further, in step c, the glycosylation reagent is selected from silver trifluoromethanesulfonate, silver oxide, silver carbonate, silver nitrate, silver perchlorate, mercuric chloride, mercuric bromide, trimethyl trifluoromethanesulfonate (TMSOTf), triethyl trifluoromethanesulfonate (TESOTf), tert-butyl dimethyl trifluoromethanesulfonate (TBSOTf), methyl trifluoromethanesulfonate, trifluoromethanesulfonic anhydride, trifluoromethanesulfonic acid, boron trifluoride ether, scandium trifluoromethanesulfonate, yttrium trifluoromethanesulfonate, copper trifluoromethanesulfonate, ferric trifluoromethanesulfonate, ferric chloride, and trichloromethanesulfonate. The mixture contains at least one of aluminum chloride, tin tetrachloride, stannous chloride, zinc chloride, zinc bromide, zinc iodide, zinc trifluoromethanesulfonate, N-iodosuccinimide (NIS), or N-bromosuccinimide (NBS); preferably, a combination of N-iodosuccinimide (NIS) and trimethylsilyl trifluoromethanesulfonate (TMSOTf), or a combination of NIS and TESOTf, or a combination of NIS and at least one of TMSOTf / TESOTf / TBSOTf. Preferably, the NIS equivalent ranges from 0.9 to 3.0 eq, more preferably 1.0 to 1.2 eq, according to Formula II-1; the TMSOTf / TESOTf / TBSOTf equivalent ranges from 0.1 to 3.0 eq, more preferably 0.2 to 0.4 eq, according to Formula II-1.

[0046] Furthermore, in step c, the reaction temperature is 0℃-50℃, preferably 10-20℃.

[0047] Glucosylation of thioglycosides places very high demands on both the substrate structure and reaction conditions. On the one hand, the thioglycoside donor needs high activity (requiring a high electronegativity at the anodic site, minimal steric hindrance at the reaction site, and high stereoselectivity controlled through neighboring group participation). Therefore, the selection and configuration of protecting groups in the thioglycoside donor intermediate structure is a major challenge in thioglycoside glycosylation. On the other hand, precise control of the type, stoichiometry, and reaction temperature of the catalyst is required to match the activity of the thioglycoside, thereby promoting efficient thioglycoside glycosylation. This part of the work also places high demands on the process. Therefore, designing activity-matched thioglycoside donors and precisely controlling the reaction process to develop simple and efficient synthetic methods for thioglycoside glycosylation is a significant and challenging task. This invention achieves thioglycosylation via intermediate I. Compared to the currently commonly used Schmidt glycosylation and Koenigs-Knorr glycosylation methods, intermediate I offers several advantages: firstly, it is more stable and can be synthesized on a large scale; secondly, the reactivity can be precisely matched by regulating the R1 group and the glycosylation reagent, resulting in higher reaction yields; and thirdly, the neighboring group participation effect allows for better control of the stereoselectivity of glycosylation. These three points enable the stable and high-yield large-scale production of intermediate II-2 compound, which can then be used to further scale up the preparation of the final product, hexaacyl-4'-monophosphoryl ester A.

[0048] A fourth object of the present invention is to provide a method for synthesizing Formula II-5, comprising the following steps:

[0049] Step d: Remove the Troc protecting groups of the 2'N atom and 3' oxygen atom from formula II-2 to obtain formula II-3;

[0050] ;

[0051] Step e: The 2' amino group of Formula II-3 selectively amidates (R)-3-(dodecanoyloxy)tetradecanoic acid (compound of Formula II-4) in the presence of an amidating condensing agent to give compound of Formula II-5.

[0052] ;

[0053] Further, in step d, the reagent for removing the Troc protecting group is zinc powder, and the zinc powder equivalent range is 5-100 eq of Formula II-3, preferably 30-50 eq.

[0054] Further, in step d, the organic solvent is one or more of dichloromethane (DCM), glacial acetic acid (HOAc), and formic acid (HCOOH), preferably glacial acetic acid (HOAc), and the amount of acetic acid used is 20-30 times the mass of the compound of formula II-2.

[0055] Furthermore, in step d, the reaction temperature is 0-50℃, preferably 30-40℃.

[0056] Further, in step e, the amidation condensation reagent is selected from one or more combinations of 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline (EEDQ), N,N'-dicyclohexylcarbodiimide (DCC), N,N'-diisopropylcarbodiimide (DIC), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI), 1-hydroxybenzotriazole (HOBT), 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate (HATU), benzotriazole-N,N,N',N'-tetramethylurea hexafluorophosphate (HBTU), or 4-dimethylaminopyridine (DMAP), preferably 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline (EEDQ); the equivalent range of EEDQ is 0.9-10.0 eq, preferably 2.0 eq.

[0057] Further, in step e, the equivalent range used in formula II-4 is 1.0-3.0eq of formula II-3, preferably 1.2-1.5eq.

[0058] Further, in step e, the reaction solvent is independently selected from one or more of dichloromethane (DCM), dichloroethane (DCE), or ethyl acetate (EA), preferably dichloromethane (DCM), and the volume range of the organic solvent dichloromethane is 10-100V, preferably 50V.

[0059] Furthermore, in step e, the reaction temperature is 0-50℃, preferably 15-25℃.

[0060] The fifth objective of this invention is to provide a method for synthesizing hexaacyl-4'-monophosphoryl ester A, comprising the following steps:

[0061] Step f: The 3' hydroxyl group of intermediate II-5 selectively reacts with compound II-6 of (R)-3-(tetradecanoyloxy)tetradecanoic acid in the presence of a condensing agent and a drying agent to give compound II-7.

[0062] ;

[0063] Step g: Compound II-7 is deprotected by a benzyl protecting group under hydrogenation catalyst conditions to obtain compound II-8;

[0064] ;

[0065] Step h: Compound II-8 is deprotected by a phenyl protecting group under the conditions of hydrogenation catalyst and hydrogen reduction to obtain hexaacyl-4'-monophosphoryl ester A (HMLA).

[0066] ;

[0067] Further, in step f, the mass ratio of the compound of formula II-5 to the compound of formula II-6 is 100:40-60, preferably 100:50-52.

[0068] Further, in step f, the condensing agent is selected from one or more of the following: 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline (EEDQ), N,N'-dicyclohexylcarbodiimide (DCC), N,N'-diisopropylcarbodiimide (DIC), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI), 1-hydroxybenzotriazole (HOBT), 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate (HATU), benzotriazole-N,N,N',N'-tetramethylurea hexafluorophosphate (HBTU), or 4-dimethylaminopyridine (DMAP), preferably a combination of DCC and DMAP. The equivalent range of the DCC used is 1.0-5.0 eq, preferably 1.3 eq; the equivalent range of the selected DMAP is 0.1-2.0 eq, preferably 1.2-1.5 eq.

[0069] Further, in step f, the desiccant is selected from one or more of 3A molecular sieve, 4A molecular sieve, 5A molecular sieve, anhydrous sodium sulfate or anhydrous magnesium chloride, preferably 4A molecular sieve; the amount of molecular sieve is 0.01-2.0M of the mass of the compound of formula II-5, preferably 1.0M.

[0070] Further, in step f, the reaction solvent is selected from one or more of dichloromethane (DCM), ethyl acetate (EA), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), toluene (PhMe), tetrahydrofuran (THF), or acetonitrile (CH3CN); preferably, the THF:HOAc ratio is 10:1.

[0071] Furthermore, in step f, the reaction temperature is 0-50℃, preferably 30-35℃.

[0072] Further, in step g, the hydrogenation catalyst is one or more of palladium / carbon, palladium hydroxide / carbon, and platinum dioxide; preferably palladium / carbon; the palladium carbon used has a palladium content of 10%, and the mass range is 0.05-2.0M of Formula II-7, preferably 0.2M.

[0073] Furthermore, in step g, the reaction temperature is 0-40℃, preferably 10-20℃.

[0074] Further, in step h, the hydrogenation catalyst is platinum dioxide, and the equivalent amount of the catalyst is 0.5-2.0 M by mass of Formula II-8, preferably 1.0 M.

[0075] Furthermore, in step h, the solvent is preferably acetic acid.

[0076] Furthermore, in step h, the reaction temperature is 10-60℃, preferably 20-25℃. Attached Figure Description

[0077] Figure 1 It is the hexaacyl-4'-monophosphoryl ester A synthesized in this invention. 1 H-NMR spectrum.

[0078] Figure 2 This is the ESI mass spectrum of hexaacyl-4'-monophosphoryl ester A synthesized in this invention.

[0079] Figure 3 This is a high-performance liquid chromatogram of hexaacyl-4'-monophosphoryl ester A synthesized in this invention. Detailed Implementation

[0080] The invention is further described below through the following non-limiting embodiments.

[0081] Example 1: Synthesis of Compound 23

[0082] ;

[0083] At 22°C, 5.0 L of dichloromethane, 1617.0 g of compound 22, and 1394.0 g of triethylsilane were added to a 30 L reactor. 371.9 g of boron trifluoride diethyl ether was slowly added dropwise with stirring. After 30 min, TLC was performed. Once the starting material had completely disappeared, the reaction solution was quenched with 3 L of water, allowed to stand, and separated. The organic phase was adjusted to neutral with 5 L of saturated sodium bicarbonate aqueous solution, washed with 2 L of saturated brine, dried over anhydrous sodium sulfate, concentrated, and purified by column chromatography. The ratio of n-heptane:ethyl acetate was 40:1 → 30:1 → 15:1 → 5:1, yielding 1400.3 g of pure, pale yellow solid compound 23, with a yield of 86.6%. 1H NMR (600 MHz, Chloroform-d) δ 7.52 –7.45 (m, 2H), 7.39 – 7.32 (m, 2H), 7.31 (s, 3H), 7.28 – 7.22 (m, 3H), 5.47(d, J = 9.1 Hz, 1H), 5.08 (t, J = 9.7 Hz, 1H), 4.93 (d, J = 10.3 Hz, 1H), 4.80 – 4.63 (m, 4H), 4.63 – 4.48 (m, 2H), 3.78 (qd, J = 10.5, 4.4 Hz, 3H), 3.72 – 3.56 (m, 2H), 3.23 (d, J = 4.4 Hz, 1H). 13 C NMR (150 MHz, Chloroform-d)δ 154.54, 154.04, 137.64, 132.58, 132.46, 129.13, 128.64, 128.19, 128.07,127.86, 95.46, 94.33, 86.18, 80.84, 77.05, 74.66, 73.87, 70.34, 70.04, 60.59,54.92. (ESI) m / z: Calcd for C 25 H 25 Cl6NO8SNa(M+Na)731.9082, found, 731.9153.

[0084] Example 2 Synthesis of Compound 24

[0085] ;

[0086] At 23°C, 8.7 L of dichloromethane, 236.2 g of triethylamine, 421.5 g of DMAP, and 1733.0 g of compound 23 were added sequentially to a 50 L reactor. Diphenyl chlorophosphate was then slowly added dropwise with stirring. After the addition was complete, the temperature was maintained at T=25°C, and the reaction was confirmed to be complete by TLC after 5 min. The reaction was quenched with 5 L of water, allowed to stand, and separated. The organic phase was washed with 2 L of saturated brine, dried over anhydrous sodium sulfate, concentrated, and purified by column chromatography (heptane:ethyl acetate = 40:1 → 30:1 → 15:1) to give 1976.6 g of pale yellow compound 24; yield 86%. HRMS (ESI) m / z:Calcd for C 74 H 68 Cl 12 N2O 22P2S2Na (2M+Na) 1911.0021, found, 1910.9043.

[0087] Example 2-2 Synthesis of Compound 26

[0088] ;

[0089] At 23°C, 400 mL of dichloromethane, 236.2 g of triethylamine, 6.1 g of DMAP, and 1733.0 g of compound 25 were added sequentially to a 1 L reaction flask. While stirring, diphenyl chlorophosphate was slowly added dropwise. After the addition was complete, the temperature was maintained at T=25°C, and the reaction was confirmed to be complete by TLC after 25 min. The reaction was quenched with 200 mL of water, allowed to stand, and separated. The organic phase was washed with 300 mL of saturated brine, dried over anhydrous sodium sulfate, concentrated, and purified by column chromatography (heptane:ethyl acetate = 40:1 → 30:1 → 15:1) to give 21.5 g of pale yellow compound 26; yield 65%, purity 94.2%. HRMS (ESI) m / z:Calcd for C 66 H 68 Cl 12 N2O 22 P2S2Na (2M+Na) 1815.7296, found, 1815.9214.

[0090] Example 3-1 Synthesis of Compound 35

[0091] ;

[0092] At 15°C, 553g of compound 34 and 633.7g of compound 24 were added to a 20L reaction flask, followed by 11L of DCM. The mixture was stirred until dissolved, then 550g of 4A molecular sieve was added, and stirring was continued for 20 minutes. Then, 160.5g of NIS and 54.4g of TMSOTf were added, and the mixture was reacted at 25°C for 1.5-3 hours. TLC analysis confirmed complete reaction of the starting materials. Triethylamine was added to adjust the pH to 7-8, and the mixture was filtered. The filter cake was washed with 2L of DCM, dried, concentrated, and purified by column chromatography (DCM:MeOH = 100:1-60:1-40:1). 958g of yellow compound 35 was obtained, with a yield of 88.3% and an HPLC purity of 99.3%. 11H NMR (600 MHz, Chloroform-d) δ 7.36 – 7.21 (m, 24H), 7.18 (t, J = 7.8 Hz, 4H), 7.14 (d, J = 8.0 Hz, 2H), 5.90 (d, J = 8.0 Hz, 1H), 5.32 (t, J = 9.8 Hz, 1H), 5.03 (p, J = 5.4, 4.8 Hz, 2H), 4.86 (t, J = 10.2 Hz, 2H), 4.83 – 4.68 (m, 5H), 4.66 (d, J = 11.3 Hz, 1H), 4.63 – 4.53 (m, 3H), 4.46 (d, J = 12.1 Hz, 1H), 4.43 – 4.33 (m, 2H), 4.14 (d, J = 11.9 Hz, 1H), 4.10 (dd, J = 11.5, 2.6 Hz, 1H), 4.00 (t, J = 8.4 Hz, 1H), 3.75 (dd, J = 11.7, 5.4 Hz, 1H), 3.69 – 3.52 (m, 6H), 3.48 (q, J = 8.9 Hz, 1H), 2.32 (dd, J = 14.9, 6.3 Hz, 1H), 2.25 (dd, J = 14.9, 5.7 Hz, 1H), 2.15 (td, J = 7.6, 2.7 Hz, 2H), 1.59 – 1.43 (m, 5H), 1.23 (dd, J = 20.4, 10.1 Hz, 51H), 0.88 (t, J = 7.0 Hz, 6H).

[0093] HRMS (ESI) m / z: Calcd for C 90 H 119 Cl6N2O 19 PNa (M+Na) 1769.5933, found, 1769.5918.

[0094] Synthesis of Compound 35 in Example 3-2

[0095] ;

[0096] At 15°C, 5.0 g of compound 34 and 5.5 g of compound 26 were added to a 250 mL reaction flask, followed by 100 mL of DCM. The mixture was stirred until dissolved, then 5.0 g of 4A molecular sieve was added, and stirring was continued for 30 minutes. Then, 1.5 g of NIS and 0.5 g of TMSOTf were added, and the mixture was reacted at 25°C for 3 hours. TLC analysis confirmed the reaction was complete. Triethylamine was added to adjust the pH to 7-8, and the mixture was filtered. The filter cake was washed with 100 mL of DCM, dried, concentrated, and purified by column chromatography (DCM:MeOH = 100:1-60:1-40:1) to obtain 2.7 g of yellow compound 35, with a yield of 58.2% and an HPLC purity of 97.8%.

[0097] Example 3-3 Synthesis of Compound 35

[0098] Other conditions were the same as in Example 3-1, except that NIS was replaced with an equivalent amount of NBS. The yield of the product compound 35 was 62.1%, with an HPLC purity of 97.3%.

[0099] Synthesis of Compound 35 in Examples 3-4

[0100] Other conditions were the same as in Example 3-1, except that TMSOTf was replaced with an equivalent amount of AgOTf. The yield of the product compound 35 was 71.5%, with an HPLC purity of 98.7%.

[0101] Synthesis of Compound 35 in Examples 3-5

[0102] Other conditions were the same as in Example 3-1, except that TMSOTf was replaced with an equivalent amount of TESOTf. The yield of the product compound 35 was 86.3%, and the HPLC purity was 99.2%.

[0103] Synthesis of Compound 35 in Examples 3-6

[0104] Other conditions were the same as in Example 3-1, except that TMSOTf was replaced with an equivalent amount of TBSOTf. The yield of the product compound 35 was 92.7%, and the HPLC purity was 99.3%.

[0105] Example 4 Synthesis of Compound 36

[0106] ;

[0107] At 23°C, 857.5 g of compound 35 was added to a 100 L reactor, followed by 17150 g of glacial acetic acid and stirring until dissolved. Then, 1598 g of zinc powder was added. After the addition was complete, the temperature was raised to 35°C and the reaction was stirred for 3-4 hours. TLC was used to confirm that the reaction was complete. 30 L of dichloromethane was added to the reaction solution for dilution, the solid was removed by filtration, and the solution was transferred to an extraction vessel. Water was added for extraction, and the organic phase was washed once with water, once with saturated sodium bicarbonate solution, and once with brine. The organic phase was concentrated and purified by column chromatography to obtain 616.9 g of compound 36, with a yield of 88.0%. 1 H NMR (600 MHz, Chloroform-d) δ 7.42 – 6.99 (m, 30H), 6.14 (s, 1H), 5.07 (q, J = 6.1 Hz, 1H), 4.93 – 4.80 (m, 2H), 4.74 (dd, J = 13.4, 7.9 Hz,2H), 4.66 (d, J = 11.4 Hz, 1H), 4.57 (t, J = 13.1 Hz, 3H), 4.54 – 4.44 (m,1H), 4.43 – 4.33 (m, 2H), 4.17 – 4.06 (m, 1H), 4.01 (dt, J = 13.6, 5.7 Hz,1H), 3.97 – 3.85 (m, 1H), 3.80 (t, J = 9.2 Hz, 1H), 3.72 (th, J = 13.7, 5.3Hz, 3H), 3.61 – 3.37 (m, 4H), 2.85 (d, J = 9.7 Hz, 1H), 2.35 (s, 1H), 2.24(dd, J = 15.1, 5.5 Hz, 1H), 2.19 – 2.07 (m, 2H), 1.52 (dt, J = 15.1, 7.2 Hz, 4H), 1.39 – 1.04 (m, 46H), 0.88 (t, J = 6.9 Hz, 6H).

[0108] HRMS (ESI) m / z: Calcd for C 82 H 113 N2O 15 PNa (M+Na)1419.7788, found,1419.7840.

[0109] Example 5 Synthesis of Compound 37

[0110] ;

[0111] 41 g of compound 36 and 18.7 g of compound 13 were weighed into a 3 L reaction flask; 1.2 L of DCM was added and stirred until dissolved, then 14.5 g of EEDQ was added. The mixture was stirred at 23 °C for 3-4 h, and TLC analysis (developing solvent: DCM: MeOH = 10:1) showed that the starting materials reacted completely. The reaction solution was concentrated, dissolved in 300 mL of DCM, and then 600 mL of acetonitrile was added to induce crystallization. The mixture was then cooled to 0 ± 5 °C and stirred for 0.5-1 h. After filtration, a filter cake was obtained. Column chromatography of the filter cake yielded 34.4 g of pale yellow compound 37, with a DCM:THF ratio of 50:1 → 30:1 → 10:1, representing a yield of 65%. 1 H NMR (600 MHz, Chloroform-d) δ 7.37 – 7.16 (m, 31H), 5.95 (d, J = 8.1Hz, 1H), 5.90 (d, J = 8.3 Hz, 1H), 5.04 (q, J = 6.1 Hz, 1H), 4.99 (dd, J =7.3, 4.7 Hz, 1H), 4.88 – 4.77 (m, 4H), 4.72 (d, J = 11.2 Hz, 2H), 4.64 (d, J= 11.4 Hz, 1H), 4.60 – 4.52 (m, 3H), 4.50 (d, J = 12.1 Hz, 1H), 4.06 (dd, J =11.4, 2.7 Hz, 1H), 3.91 (t, J = 8.5 Hz, 1H), 3.80 – 3.74 (m, 2H), 3.74 – 3.69(m, 3H), 3.68 – 3.63 (m, 2H), 3.60 (ddd, J = 8.5, 5.6, 2.6 Hz, 1H), 3.57 –3.51 (m, 1H), 3.44 (dd, J = 9.3, 4.4 Hz, 1H), 2.38 – 2.27 (m, 2H), 2.27 –2.19 (m, 2H), 2.19 – 2.07 (m, 5H), 1.58 (s, 5H), 1.56 – 1.45 (m, 8H), 1.32 –1.04 (m, 82H), 0.87 (td, J = 7.1, 1.8 Hz, 12H). HRMS (ESI) m / z: Calcd forC 108 H 161 N2O 18 PNa (M+Na)1829.1516, found, 1829.1423.

[0112] Example 6 Synthesis of Compound 38

[0113] ;

[0114] Weigh 10.0 g DCC, 100 g compound 37, 50.3 g compound 14, 100 g molecular sieve, and 3.5 L toluene into a 10 L reaction flask; stir until dissolved; stir at 30-35 °C for 30 min, add 5 g DMAP, raise the temperature to T=85 °C, and maintain the temperature for 4-5 h. TLC shows that the reaction of the starting material has disappeared. Cool the system to room temperature, add DCM for dilution, filter, elute the filter cake with DCM, concentrate the filtrate, and purify by column chromatography. The ratio of DCM:MeOH is 20:1 → 15:1 → 10:1 to obtain 9.4 g of pale yellow compound 38, with a yield of 75.7%.

[0115] 1H NMR (600 MHz, Chloroform-d) δ 7.34 – 7.22 (m, 24H), 7.18 – 7.07(m, 6H), 6.08 (d, J = 7.8 Hz, 1H), 5.85 (dd, J = 18.0, 8.3 Hz, 1H), 5.50 –5.41 (m, 1H), 5.14 (td, J = 8.7, 3.6 Hz, 1H), 5.06 (dt, J = 23.0, 7.3 Hz, 3H), 5.02 – 4.91 (m, 1H), 4.89 – 4.80 (m, 2H), 4.77 (t, J = 7.8 Hz, 1H), 4.70(ddd, J = 15.7, 10.4, 6.3 Hz, 3H), 4.63 (d, J = 11.4 Hz, 1H), 4.61 – 4.53 (m,2H), 4.44 (t, J = 4.8 Hz, 1H), 4.35 (d, J = 2.6 Hz, 1H), 4.06 (td, J = 11.4,5.4 Hz, 1H), 3.93 – 3.84 (m, 1H), 3.78 (dd, J = 11.3, 5.6 Hz, 1H), 3.76 –3.72 (m, 1H), 3.70 (q, J = 8.4 Hz, 1H), 3.59 (dd, J = 9.3, 3.4 Hz, 3H), 3.57– 3.52 (m, 3H), 3.52 – 3.46 (m, 1H), 2.45 – 2.07 (m, 12H), 1.67 – 1.38 (m,15H), 1.23 (qt, J = 16.5, 5.7 Hz, 127H), 0.87 (td, J = 7.1, 2.4 Hz, 18H).

[0116] Maldi (m / z): Calculated for C 136 H 213 N2O 21 P (M+Na)2265.5432, found, 2265.541.

[0117] Example 7 Synthesis of Compound 39

[0118] ;

[0119] 50 g of compound 38 was added to a 5 L reaction flask, followed by 250 mL of THF and stirring until dissolved. 10 g of Pd / C and 2500 mL of glacial acetic acid were added, and the mixture was purged with hydrogen. The temperature was raised to 16 °C and maintained for 5 h. TLC analysis showed the starting material had disappeared. Pd / C was removed by filtration. The filtrate was diluted with water, extracted three times with 2 L of ethyl acetate, dried, and concentrated to obtain 36.48 g of crude compound 39. The crude product yield was 87%, and it was directly used for the next step. HRMS (ESI) m / z: Calcd for C 108 H 189 N2O 21 PNa (M+Na) 1905.3554, found, 1905.3468.

[0120] Example 8 Synthesis of Compound 40

[0121] ;

[0122] 10g of crude compound 39 was dissolved in 500mL of acetic acid, 10g of PtO2 was added, hydrogen was added, and the reaction was carried out at 22℃ for 4h. The starting material was completely eliminated in the TLC. The mixture was filtered, and the filter cake was washed with 50mL of acetic acid and then with 50mL of acetonitrile. The filter cake was dissolved in 50mL of THF, centrifuged, and the supernatant was collected and concentrated to obtain the crude product. The crude product was dissolved in 50mL of DCM, and 50mL of acetonitrile was added dropwise to induce crystallization. The mixture was filtered, and the filter cake was washed with acetonitrile and dried to obtain 8.08g of white solid compound 40, with a yield of 88% and a purity of 98.7%. 1H NMR (600 MHz, Methanol-d4) δ 5.21 – 5.09 (m, 3H), 5.06 (dd, J = 7.5, 4.4 Hz, 1H), 5.01 (d,J = 3.6 Hz, 1H), 4.60 (d, J = 8.5 Hz, 1H), 4.19 (q, J = 9.7 Hz, 1H), 4.07 (q,J = 7.2 Hz, 1H), 4.00 (dd, J = 11.5, 2.1 Hz, 1H), 3.90 (ddd, J = 9.0, 6.5,2.0 Hz, 1H), 3.84 – 3.72 (m, 4H), 3.68 – 3.57 (m, 2H), 3.40 (dt, J = 9.7, 3.2Hz, 1H), 3.30 (p, J = 1.6 Hz, 1H), 3.27 – 3.20 (m, 1H), 2.60 (dd, J = 16.5,7.5 Hz, 1H), 2.52 (dd, J = 16.5, 5.3 Hz, 1H), 2.48 – 2.37 (m, 3H), 2.34 –2.19 (m, 8H), 1.54 (ddt, J = 20.2, 12.9, 7.0 Hz, 12H), 1.37 – 1.16 (m, 114H), 0.83 (t, J = 6.9 Hz, 18H).HRMS (ESI) m / z: Calcd for C 96 H 180 N2O 21 P (MH)1729.2928, found, 1729.2736.

[0123] Figure 1 It is the hexaacyl-4'-monophosphoryl ester A synthesized in this invention. 1 H-NMR spectrum. Figure 2 This is the ESI mass spectrum of hexaacyl-4'-monophosphoryl ester A synthesized in this invention. Figure 3 This is a high-performance liquid chromatogram of hexaacyl-4'-monophosphoryl ester A synthesized in this invention. It can be confirmed that compound 40 obtained in Example 8 is the target product.

Claims

1. An intermediate I for the synthesis of hexaacyl-4'-monophosphoryl ester A, characterized in that, The structural formula is as follows: ； Wherein, R1 is selected from C1-6 alkyl and phenyl optionally substituted with C1-6 alkyl; Bn represents benzyl, Troc represents trichloroethoxyformyl; preferably, R1 includes methyl, ethyl, propyl, phenyl, p-methylphenyl, o-methylphenyl or m-methylphenyl.

2. The method for synthesizing intermediate I according to claim 1, characterized in that, Includes the following steps: Step a: In the presence of a reducing agent and an acidic agent, selectively reduce the exposed 4-hydroxyl group at the benzylmethylene protecting group at positions 4 and 6 in Formula I-1 to obtain Formula I-2; ； Step b: In the presence of a phosphorylating agent and a basic agent, the exposed hydroxyl group at position 4 of formula I-2 is phosphorylated to obtain thioglycoside donor intermediate I; 。 3. The synthesis method according to claim 2, characterized in that, In step a, the selected reducing agent is one or more of the following: trimethylsilane (Me3SiH), triethylsilane (Et3SiH), triphenylsilane (Ph3SiH), borane (BH3), boranetetrahydrofuran (BH3·THF), diphenylborane chloride (Ph2BCl), and sodium cyanoborohydride (NaBH3CN), preferably triethylsilane (Et3SiH); the equivalent amount of Et3SiH is in the range of 2.0-8.0 eq; the acidic agent is selected from aluminum trichloride (AlCl3). The following are one or more combinations of hydrochloric acid (HCl), trifluoromethanesulfonic acid (TfOH), boron trifluoride ether (BF3·OEt), silver trifluoromethanesulfonate (AgOTf), trimethylsilyl trifluoromethanesulfonate (TMSOTf), triethylsilyl trifluoromethanesulfonate (TESOTf), or tert-butyldimethylsilyl trifluoromethanesulfonate (TBSOTf), preferably BF3·OEt2; the equivalent of BF3·OEt2 used is 0.5-3.0 eq of Formula I-1, preferably 1-1.15 eq; Further, in step a, the reaction solvent is one or more of the following: dichloromethane (DCM), tetrahydrofuran (THF), dioxane, diethyl ether (Et2O) or toluene (PhMe), preferably dichloromethane (DCM). Furthermore, in step a, the reaction temperature range is 10-40℃, preferably 20-25℃; Furthermore, in step b, the reaction solvent is one or more of dichloromethane (DCM), dichloroethane (DCE), or ethyl acetate (EA), or any combination thereof; Further, in step b, the phosphorylating agent is diphenyl chlorophosphate, and the reaction equivalent range is 1.0-4.0 eq of Formula I-2, preferably 1.5 eq; Further, in step b, the alkaline reagent is selected from one or more of triethylamine, diisopropylamine or diisopropylethylamine, preferably triethylamine; the amount used is 0.5-10 eq of formula I-2; Furthermore, in step b, the reaction temperature is 5-50℃, preferably 10-25℃.

4. A method for synthesizing a compound of formula II-2, characterized in that, Includes the following steps: Step c: The compound of formula II-1 and intermediate I of claim 1 are reacted in the presence of a glycosylation agent to obtain formula II-2; 。 5. The synthesis method according to claim 4, characterized in that, The mass ratio of compound II-1 to intermediate I is 1:1.0-1.5, preferably 1:1.1-1.

2.

6. The synthesis method according to claim 4, characterized in that, The reaction solvent is one or more of dichloromethane (DCM), dichloroethane (DME), diethyl ether (Et2O) or toluene (PhMe), preferably dichloromethane (DCM); Furthermore, the reaction temperature is 0℃-50℃, preferably 10-20℃; Further, in step c, the glycosylation reagent is selected from silver trifluoromethanesulfonate, silver oxide, silver carbonate, silver nitrate, silver perchlorate, mercuric chloride, mercuric bromide, trimethylsilyl trifluoromethanesulfonate, triethylsilyl trifluoromethanesulfonate, tert-butyldimethylsilyl trifluoromethanesulfonate, methyl trifluoromethanesulfonate, trifluoromethanesulfonic anhydride, trifluoromethanesulfonic acid, boron trifluoride ether, scandium trifluoromethanesulfonate, yttrium trifluoromethanesulfonate, copper trifluoromethanesulfonate, ferric trifluoromethanesulfonate, ferric chloride, aluminum trichloride, tin tetrachloride, and stannous chloride. At least one of zinc chloride, zinc bromide, zinc iodide, zinc trifluoromethanesulfonate, N-iodosuccinimide (NIS) or N-bromosuccinimide (NBS); preferably a combination of N-iodosuccinimide (NIS) and trimethylsilyl trifluoromethanesulfonate (TMSOTf), or a combination of NIS and TESOTf, or a combination of NIS and TBSOTf, or a combination of NIS and at least one of TMSOTf / TESOTf / TBSOTf.

7. The synthesis method according to claim 6, characterized in that, The NIS equivalent range is 0.9-3.0eq from Equation II-1, preferably 1.0-1.2eq; the total equivalent range of TMSOTf / TESOTf / TBSOTf is 0.1-3.0eq from Equation II-1, preferably 0.2-0.4eq.

8. A method for synthesizing Formula II-5, comprising the following steps: Step d: The compound of formula II-2 synthesized by any one of claims 4-7 is deprotected by the Troc protecting group of the 2'N atom and the 3' oxygen atom to obtain formula II-3; ； Step e: The 2' amino group of formula II-3 selectively amidates (R)-3-(dodecanoyloxy)tetradecanoic acid (compound of formula II-4) in the presence of an amidating condensing agent to give compound II-5; ； Further, in step d, the reagent for removing the Troc protecting group is zinc powder, and the zinc powder equivalent range is 5-100 eq of Formula II-3, preferably 30-50 eq; Further, in step d, the organic solvent is one or more of dichloromethane (DCM), glacial acetic acid (HOAc), and formic acid (HCOOH), preferably glacial acetic acid (HOAc), and the amount of acetic acid used is 20-30 times the mass of the compound of formula II-2; Furthermore, in step d, the reaction temperature is 0-50℃, preferably 30-40℃; Further, in step e, the amidation condensation reagent is selected from one or more combinations of 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline (EEDQ), N,N'-dicyclohexylcarbodiimide (DCC), N,N'-diisopropylcarbodiimide (DIC), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI), 1-hydroxybenzotriazole (HOBT), 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate (HATU), benzotriazole-N,N,N',N'-tetramethylurea hexafluorophosphate (HBTU), or 4-dimethylaminopyridine (DMAP), preferably 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline (EEDQ); the equivalent range of EEDQ is 0.9-10.0 eq, preferably 2.0-3.0 eq; Further, in step e, the equivalent range used in formula II-4 is 1.0-3.0eq of formula II-3, preferably 1.2-1.5eq; Further, in step e, the reaction solvent is independently selected from one or more of dichloromethane (DCM), dichloroethane (DCE) or ethyl acetate (EA), with dichloromethane (DCM) being preferred. Furthermore, in step e, the reaction temperature is 0-50℃, preferably 15-25℃.

9. A method for synthesizing hexaacyl-4'-monophosphoryl ester A, characterized in that, Includes the following steps: Step f: The 3'-hydroxyl group of the intermediate compound II-5 obtained by the synthetic method of claim 8 selectively reacts with compound II-6 of (R)-3-(tetradecanoyloxy)tetradecanoic acid in the presence of a condensing agent and a drying agent to obtain compound II-7. ； Step g: Compound II-7 is deprotected by a benzyl protecting group under hydrogenation catalyst conditions to obtain compound II-8; ； Step h: Compound II-8 is deprotected by a phenyl protecting group under the conditions of hydrogenation catalyst and hydrogen to give hexaacyl-4'-monophosphoryl ester A (HMLA); ； Further, in step f, the mass ratio of the compound of formula II-5 to the compound of formula II-6 is 100:40-60, preferably 100:50-52; Further, in step f, the condensing agent is selected from one or more of the following: 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline (EEDQ), N,N'-dicyclohexylcarbodiimide (DCC), N,N'-diisopropylcarbodiimide (DIC), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI), 1-hydroxybenzotriazole (HOBT), 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate (HATU), benzotriazole-N,N,N',N'-tetramethylurea hexafluorophosphate (HBTU), or 4-dimethylaminopyridine (DMAP), preferably a combination of DCC and DMAP. The equivalent range of the DCC used is 1.0-5.0 eq, preferably 1.3 eq; the equivalent range of the selected DMAP is 0.1-2.0 eq, preferably 1.2-1.5 eq; Further, in step f, the desiccant is selected from one or more of 3A molecular sieve, 4A molecular sieve, 5A molecular sieve, anhydrous sodium sulfate or anhydrous magnesium chloride, with 4A molecular sieve being preferred; The amount of molecular sieve used is 0.01-2.0 M of the mass of the compound of formula II-5, preferably 1.0 M; Further, in step f, the reaction solvent is one or more of the following: dichloromethane (DCM), ethyl acetate (EA), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), toluene (PhMe), tetrahydrofuran (THF), or acetonitrile (CH3CN); preferably, the ratio of THF:HOAc is 10:

1. Furthermore, in step f, the reaction temperature is 0-50℃, preferably 30-35℃; Further, in step g, the hydrogenation catalyst is selected from palladium / carbon, palladium hydroxide / carbon, and platinum dioxide; preferably palladium / carbon; the palladium carbon used has a palladium content of 10%, and the mass range is 0.05-2.0M of Formula II-7, preferably 0.2-0.5M; Furthermore, in step g, the reaction temperature is 0-40℃, preferably 10-20℃; Further, in step h, the hydrogenation catalyst is platinum dioxide, and the equivalent amount of the catalyst is 0.5-2.0 M by mass of Formula II-8, preferably 1.0-1.5 M; Furthermore, in step h, the solvent is preferably acetic acid; Furthermore, in step h, the reaction temperature is 10-60℃, preferably 20-25℃.

10. Use of intermediate I in the synthesis of hexaacyl-4'-monophosphoryl ester A; the structural formula of intermediate I is shown below: ； in, R1 is a phenyl group selected from C1-6 alkyl groups and optionally substituted with C1-6 alkyl groups; Bn represents benzyl, Troc represents trichloroethoxyformyl; R1 includes methyl, ethyl, propyl, phenyl, p-methylphenyl, o-methylphenyl or m-methylphenyl; Furthermore, the aforementioned application is achieved through the following synthetic route: ； ； ； ； ； ； ； 。

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