Molecular surgery: cut-insert-stitch editing reaction (cister) technique

Abstract

The present invention generally relates to the field of organic synthesis. Particularly, the present invention relates to a cut-insert stitch-editing reaction (CIStER) process to stereo- and regioselectively synthesize complex and branched glycoconjugates. The present invention also relates to a process of one pot-three step chemical approach to synthesize lipoarabinomannan analogs present in Mycobacterium tuberculosis.

Description

MOLECULAR SURGERY: CUT-INSERT-STITCH EDITING REACTION (CIStER) TECHNIQUEFIELD OF THE INVENTION

[0001] The present invention generally relates to the field of organic synthesis chemistry. Particularly, the present invention relates to a cut-insert-stitch editing reaction (CIStER) process to stereo- and regioselectively synthesize complex and branched glycoconjugates and other molecules. The present invention also relates to a process of one pot-three step chemical approach to synthesize lipoarabinomannan analogs present in the cell wall of Mycobacterium tuberculosis.BACKGROUND OF THE INVENTION

[0002] Nucleic acids, proteins, carbohydrates, and lipids exist among the numerous biomolecules produced by living organisms, and occur in myriad sizes and structures. These biomolecules perform several biological functions, and have been extensively investigated. Additionally, nucleic acid chemistry has matured because of the development of excellent molecular biology tools, such as recombinant DNA technology, polymerase chain reaction, DNA amplification, CRISPR-editing, and prime editing. The tools have had an oblique impact on the synthesis of proteins as a direct consequence of the central dogma. Genomic editing techniques play a pivotal role in many fields, such as, agriculture, the discovery of pharmaceuticals and diagnostic tools, production of biofuels, and enable a better understanding of disease biology.

[0003] Carbohydrates are ubiquitous and impart several biological effects, including signal transduction, cell-cell communication, and development. Carbohydrates exist as conjugates of glycans and aglycons, wherein the aglycon can be a protein, as in glycoproteins; a lipid, as in glycolipids; or a steroid, as in saponins. The isolation of carbohydrates from natural systems is complicated because natural systems are innately microheterogeneous, and postsynthetic correction, amplification, and modification of synthetic or natural glycans are still nascent.

[0004] Some of the most powerful approaches that have emerged for saccharide editing in glycotechnology are, skeletal editing by the acid-catalyzed transformation of furanosides to pyranosides, Ferrier rearrangement for converting carbohydrates to cyclitols, sugar-to-sugar transformations by oxidation followed by reduction as shown in figure below, uncontrolled editing of cell surface glycans by metabolic oligosaccharide engineering (MOE), andenzymatic addition of glycans (EAG). In MOE cells are cultured with a monosaccharide containing a reporter moiety (e.g., alkyne / azide), theorizing that the conjugate of the reporter moiety and monosaccharide is incorporated into its cellular processes; the incorporated moiety can guide the investigation of biological pathways, including cell imaging by using bioorthogonal chemistry as shown in the figure below. This technique has been utilized for cell imaging and probing biosynthetic machinery. By contrast, EAG exploits the site-specific cleavage of glycosidic bonds by designer glycosidases, and the resulting hydrolyzed glycans are further subjected to glycosyl transferases as post-synthetic modifications to attach new glycans / probes as shown in the figure below. To the best of our knowledge, there is no editing technique that enables the insertion of a foreign glycan into already-synthesized glycans via chemical or enzymatic routes.

[0005] Despite the challenges associated with the synthesis of glycoconjugates many innovative developments using chemical or enzymatic reactions have occurred over the past century; additionally, good quality control was accomplished. The key reaction in the assembly of oligosaccharides is glycosidation, in which a glycosyl donor and aglycon are condensed to form a glycosidic bond. Glycosyl donors often contain an appendage at the anomeric carbon (Cl), that can be activated by the addition of promoters to obtain a highly reactive oxocarbenium ion intermediate; the oxocarbenium ion intermediate can be attacked by an aglycon to afford a glycoside. Many pioneering efforts have culminated in the development of glycosyl donor chemistry. Moreover, previously reported glycosyl donors have been revived by modem reagents using either stoichiometric or catalytic amounts of the reagent(s). In addition to these developments, linear and convergent strategies have been formulated for glycan assembly using latent, iterative, catalytic, or orthogonal activation protocols.

[0006] Synthesis of carbohydrates is still a challenging task in spite of the first glycoside synthesis about a century ago by Emil Fischer. A lot of progress has been made till now to democratize the glycosidation reaction by inventing methods that require stoichiometric quantity to catalytic amounts of reagents by adopting linear or convergent approaches by solid phase, continuous flow, latent activation, orthogonal activation strategies. Bourgeoning developments in the glycobiology warranted high demand for rapid synthesis of glycoconjugates. Traditional methods of glycoconjugates syntheses require step-wise assembly of glycans. Rapid synthesis of glycans by insertion or deletion is still a distant dream for all carbohydrate chemistry.

[0007] Therefore, there is a need in the art to provide an improved process for synthesis of the glycoconjugates using cut-insert reaction techniques which is simple and fast.OBJECTIVES OF THE INVENTION

[0008] The main objective of the present invention is to develop a process of one pot-three step chemical approach for stereo- and regio-selectively synthesize complex and branched glycoconjugates.

[0009] Another objective of the present invention is to develop a process of one pot-three step chemical approach for stereo- and regioselectively synthesize complex and branched glycoconjugates using a cut-insert stitch-editing reaction (CIStER).

[0010] Another objective of the present invention is to provide a process of preparing glycohybrids using CIStER technique.

[0011] Another objective of the present invention is to provide a gram scale synthesis of 6- galactosyl lactose from lactose using CIStER technique.

[0012] Another objective of the present invention is to provide a process of preparation of linear and branched oligosaccharides using CIStER technique.

[0013] Another objective of the present invention is to synthesize lipoarabinomannan analogs present in Mycobacterium tuberculosis using a cut-insert stitch-editing reaction (CIStER).SUMMARY OF THE INVENTION

[0014] The present invention relates to a cut-insert stitch-editing reaction (CIStER) process to stereo- and region-selectively synthesize complex and branched glycoconjugates. The present invention also relates to a process of one pot-three step chemical approach to synthesize lipoarabinomannan analogs present in Mycobacterium tuberculosis.

[0015] The present invention provides one pot-three step chemical approach to stereo- and regioselectively synthesize complex and branched glycoconjugates. Inventors have used a cut-insert stitch-editing reaction (CIStER) technique to surgically edit branched and linear glycans. The reaction comprises three steps and cutting an interglycosidic bond in a regiospecific manner, inserting a foreign glycan, and stitching the glycosidic bond to obtain a hybrid glycan. Additionally, the CISTER is successfully used to synthesize lipoarabinomannan analogs present in Mycobacterium tuberculosis. The present invention makes a significant contribution to the literature because lipoarabinomannan is a strong antigenic epitope present in the cell wall of Mycobacterium tuberculosis (Mtb) and is being considered as a target for the development of vaccines and diagnostic tools.

[0016] In an aspect, the present invention relates to a process for synthesis of the glycoconjugates using a cut-insert stitch-editing reaction (CIStER) comprising the steps of:(a) cutting an interglycosidic bond of saccharide compound in a regiospecific manner using pTolSH and BF3Et2O in a solvent to afford thiotolyl gentiobiose and monosaccharide;(b) inserting Janus glycosyl acceptor donor compounds with thiotolyl gentiobiose in presence of reagent NIS / AgOTf and solvent to obtain janus-saccharides compound; and(c) stitching the janus-saccharides compound obtained in step (b) with monosaccharide in presence of [Au] / [Ag] catalyst and solvent to obtain stitched product, glycoconjugates.

[0017] In an aspect, the present invention relates to a process for synthesis of the glycoconjugates using a cut-insert stitch-editing reaction (CIStER) comprising the steps of:(a) cutting an interglycosidic bond of trisaccharide compound (5) in a regiospecific manner using pTolSH and BF3Et2O to afford thiotolyl gentiobiose (10) and monosaccharide (7);(b) inserting janus glycosyl acceptor donor compounds (6) with thiotolyl gentiobiose (10) in presence of reagent NIS / AgOTf and solvent to obtain trisaccharides compound (8); and(c) stitching the trisaccharides compound (8) obtained in step (b) with monosaccharide (7) in presence of [Au] / [Ag] catalyst and solvent to obtain stitched product, tetra- and pentasaccharide, glycoconjugates (11).

[0018] In an embodiment of the present invention, the trisaccharide compound (5) is

[0019] In another embodiment of the present invention, the thiotolyl gentiobiose (10) and monosaccharide (7) is

[0020] In another embodiment of the present invention, the Janus glycosyl acceptor donor compounds (6) is:

[0021] In another embodiment of the present invention, the trisaccharides compound (8) is:

[0022] In another embodiment of the present invention, the stitched product, tetra- and pentasaccharide, glycoconjugates is selected from the group consisting of:BRIEF DESCRIPTION OF THE FIGURES

[0023] Figure 1 represents the liquid chromatographs of CIStER reaction products 1 la-1 If.

[0024] Figure 2 represents the liquid chromatographs of CIStER reaction products 13-16.

[0025] Figure 3 represents the liquid chromatographs of CIStER reaction products 23-27.DETAILED DESCRIPTION OF THE INVENTION

[0026] The following is a detailed description of embodiments of the disclosure. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.

[0027] Unless the context requires otherwise, throughout the specification which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”

[0028] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0029] In an embodiment, the present invention relates to a process for synthesis of the glycoconjugates using a cut-insert stitch-editing reaction (CIStER) comprising the steps of:(a) cutting an interglycosidic bond of saccharide compound in a regiospecific manner using pTolSH and BF3Et2O in a solvent to afford thiotolyl gentiobiose and monosaccharide;(b) inserting Janus glycosyl acceptor donor compounds with thiotolyl gentiobiose in presence of reagent NIS / AgOTf and solvent to obtain janus-saccharides compound; and(c) stitching the janus-saccharides compound obtained in step (b) with monosaccharide in presence of [Au] / [Ag] catalyst and solvent to obtain stitched product, glycoconjugates.

[0030] In another embodiment of the present invention, the solvent used in the step (a) dichloromethane, CH3CN, CHC13, Toluene, THF, and the like.

[0031] In another embodiment of the present invention, the solvent used in the step (b) dichloromethane, CH3CN, CHC13, Toluene, THF, and the like.

[0032] In another embodiment of the present invention, the solvent used in the step (c) dichloromethane, CHCl , Toluene, THF, and the like.

[0033] In another embodiment of the present invention, the Ag / Au catalyst is chloro[tris(2,4- ditbutylphenyljphosphite] gold(I) / silver trifluoromethanesulfonate.

[0034] In another embodiment, the process for synthesis of the glycoconjugates using a cutinsert stitch-editing reaction (CIStER) is shown in the scheme- 1 below.Scheme-1

[0035] In another embodiment, the present invention provides a process of cutting of the interglycosidic bonds in naturally occurring disaccharides, as per scheme 2 below.Scheme-2

[0036] In another embodiment, the present invention provides a process of preparing glycohybrids using CIStER technique as per Scheme -3 below.Scheme-3

[0037] In another embodiment, the present invention provides a gram scale synthesis of 6- galactosyl lactose from lactose using CIStER technique as shown in the Scheme-4 below.Scheme-4 0Ac22 (71%)

[0038] In another embodiment, the present invention provides synthesis of linear and branched oligosaccharides using CIStER technique as shown in the Scheme-5 below.Scheme-5

[0039] In another embodiment, the present invention relates to a process for synthesis of the glycoconjugates using a cut-insert stitch-editing reaction (CIStER), wherein the process comprises the steps of:(a) cutting an interglycosidic bond of trisaccharide compound (5) in a regiospecific manner using TolSH and BF3Et2O to afford thiotolyl gentiobiose (10) and monosaccharide (7);(b) inserting Janus glycosyl acceptor donor compounds (6) with thiotolyl gentiobiose (10) in presence of reagent NIS / AgOTf and solvent to obtain trisaccharides compound (8); and(c) stitching the trisaccharides compound (8) obtained in step (b) with monosaccharide (7) in presence of [Au] / [Ag] catalyst and solvent to obtain tetra- and pentasaccharide, glycoconjugates (11).

[0040] In another embodiment of the present invention, the glycoconjugates are selected from the group consisting of:Methyl-2, 3, 6-tri-O-benzoyl-4-O-(2-O-benzoyl 3,4-di-O-benzyl 6-O-(2,3,4-tri-O-benzyl-6- O-(2,3,4,6-tetra-O-benzoyl-P-D-glucopyranosyl)-a-D- mannopyranosyl)-a-D- mannopyranosyl)-a-D-glucopyranoside (1 la);Methyl-2, 3, 6-tri-O-benzoyl-4-O-(2, 3, 4-tri-O-benzyl-6-O-(2, 3, 4-tri-O-benzyl-6-O-(2, 3,4,6- tetra-O-benzoyl-P-D-glucopyranosyl)-a-D-mannopyranosyl)-a / p-D-glucopyranosyl)-a-D- glucopyranoside (11b);Methyl-2, 3, 6-tri-O-benzoyl-4-O-(2, 3, -di-O-benzoyl-5-O-(2, 3, 4-tri-O-benzyl-6-O-(2, 3,4,6- tetra-O-benzoyl-P-D-glucopyranosyl)-a / p-D-mannopyranosyl)-a-D-arabinofuranosyl)-a-D- glucopyranoside (11c);Methyl-2, 3, 6-tri-O-benzoyl-4-O-(2, 3-di-O-benzoyl 5-O-(2,3,4-tri-O-benzyl-6-O-(2,3,4,6- tetra-O-benzoyl-P-D-glucopyranosyl)-a-D- mannopyranosyl)-P-D-ribofuranosyl)-a-D- glucopyranoside (l id);Methyl-2, 3, 6-tri-O-benzoyl-4-O-(2, 3-di-O-benzoyl 5-0- (2, 3-di-O-benzoyl 5-0 -(2,3,4-tri- O-benzyl-6-O-(2,3,4,6-tetra-O-benzoyl-P-D-glucopyranosyl)-a / p -D-mannopyranosyl)-a-D- arabinofuranosyl)-a-D-arabinofuranosyl)-a-D-glucopyranoside (1 le);Methyl-2, 3, 6-tri-O-benzoyl-4-O-(2, 3, 6-tri-O-benzyl-4-O-(2, 3, 4-tri-O-benzyl-6-O-(2, 3,4,6- tetra-O-benzoyl-P-D-glucopyranosyl)-a-D-mannopyranosyl)-a / p-D-glucopyranosyl)-a-D- glucopyranoside (I lf);Methyl 2,3,6-tri-O-benzyl-4-O-(2,3,4,6-tetra-O-benzylglucopyranosyloxyhexanoyl)-a-D- glucopyranoside (19a);Methyl 2,3,6-tri-O-benzyl-4-O-(2lS'-((benzyloxy)carbonyl)amino-(3-(2,3,4,6-tetra-O-benzyl glucopyranosyloxy))propanoyl) a-D-glucopyranoside (19b);Methyl 2,3,6-tri-O-benzyl-4-O-((42?)-4-((32?,82?,95,105,132?,145,172?)-3-(2,3,4,6-tetra-O- benzylglucopyranosyloxy)- 10,13 -dimethylhexadecahydro- lH-cyclopenta[a]phenanthren- 17- yl)pentanoyl) a-D-glucopyranoside (19c);P-D-galactopyranosyl-( 1 -^6)-P-D-galactopyranosyl-( 1 -^4)-a / p-D-glucopyranose (22);Allyl-3,4,6-tri-O-benzyl-2-O-(2, 3 di-O-benzoyl -5-O-(2, 3-di-O-benzoyl-5-O-(2,3-di-O- benzoyl-5 -O-(2,3-di-O-benzoyl-5 -O-(2,3 -di-O-benzoyl-5 -O-(2,3 -di-O-benzoyl-5 -O-(2,3-di- O-benzoyl-5-O-(2,3,4-tri-O-benzyl-6-O-(2,3,4,6-tetra-O-benzoyl-a-D-mannopyranosyl)-a / p- D-mannopyranosyl)-a-D-arabinofuranosyl)-a-D-arabinofuranosyl)-a-D-arabinofuranosyl)-a- D-arabinofuranosyl)-a-D-arabinofuranosyl)-a-D-arabinofuranosyl)-a-D-arabinofuranosyl)-a- D- Mannopyranoside (25); andAllyl-3,4,6-tri-O-benzyl-2-O- (3, 5-di-O-(2, 3-di-O-benzoyl-5-O-(2,3-di-O-benzoyl-5-O-(2,3- di-O-benzoyl-5-O-(2,3,4,-tetra-O-benzyl-6-O-(2,3,4,6-tetra-O-benzoyl-a-D- mannopyranosyl)-a / p-D-mannopyranosyl)-a-D-arabinofuranosyl)-a-D-arabinofuranosyl)-a- D-arabinofuranosyl)-a-D-Mannopyranoside (27).

[0041] In another embodiment of the present invention, the process is one pot process.

[0042] According to the present invention, the CIStER technique requires the identification of a pair of orthogonally activatable stable glycosyl donors that can produce the desired glycosidic linkages in a chemo-specific manner with faster kinetics. Considering the suite ofglycosylation protocols with stable glycosyl donors, the activation of alkynyl glycosyl carbonates by [Au] / [Ag] catalysts and thioglycosides by thiophilic reagents shows promise, because the activation affords glycosides rapidly and in higher yields. Furthermore, finetuning of the reactivity and selectivity can be accomplished by placing substituents that display the -I or +1 effect at the C2-position.

[0043] In another embodiment of the present invention, the glycans can be surgically edited using CIStER. Such CIStER processes require thorough planning of the guide glycan and subtle stereoelectronic factors, leading to alterations in their interglycosidic bonds that undergo hydrolysis. CIStER is based on the activation of glycosyl donors by trapping the oxocarbenium ion intermediate with a nucleophile (pTolSH) that can be orthogonally activated in the presence of an aglycon equipped with another leaving group (ethynylcyclohexyl carbonate) to afford a new glycoside. Subsequently, ethynylcyclohexyl carbonate was activated to stitch the glycan and obtain a library of higher oligosaccharides in a surgical manner. Using the CIStER methodology a library of new glycohybrids could be produced that are powerful probes to unravel new biological pathways, and enhancing our current understanding thereof. Extension of CIStER methodology for small molecules is currently underway

[0044] While the foregoing describes various embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.EXAMPLES

[0045] The present invention is further explained in the form of following examples. However, it is to be understood that the following examples are merely illustrative and are not to be taken as limitations upon the scope of the invention.General methods

[0046] Unless otherwise noted, materials were obtained from commercial suppliers and were used without further purification. Gold-phosphite catalyst was purchased from Proactive Molecular Research, Florida (USA) and AgOTf was purchased from Sigma-Aldrich. All the moisture sensitive reactions were performed in flame dried glassware under nitrogen or argon atmosphere unless stated otherwise. 4A molecular sieves were activated by heating at 150-200 °C under high vacuum for 4 h before storing in a dry desiccator. Freshly distilled CH2CI2 was stored over activated 4A molecular sieves (preheated to 200-250 °C). The reactions were monitored by analytical thin layer chromatography (TLC) performed on 0.25 mm Merck silica gel plates (60F254) under 254 nm UV lamp and stained by anisaldehyde stain. Removal of solvent in vacuo refers to distillation using a rotary evaporator attached to an efficient vacuum pump. Column chromatography of the crude compounds was performed on silica gel of 100-200 mesh (75-150 pm). Products obtained as solids or syrups were dried under high vacuum. Optical rotations were measured on digital polarimeter at 25 °C in CHC13 solution. IR spectra were recorded on a FT-IR spectrometer. NMR spectra were recorded either on a 400 or 600 MHz with CDC13 as the solvent and TMS as the internal standard. High resolution mass spectroscopy (HRMS) was performed using an ESI-TOF mass analyzer or MALDI-TOF mass analyzer. Normal Phase HPLC purifications were performed using Gilson’s PLC 2050 series.Example 1: Deprotection of Allyl Glycosides:

[0047] To a solution of the allyl glycoside (1.0 mmol) in CH2C12 / MeOH (1:4 in 10 mL), a solution of PdC12 (0.3 mmol) in MeOH (6 mL) was added and the reaction mixture was stirred at 25 °C for 5 h. After complete conversion, the reaction mixture was neutralized by the addition of excess Et3N (~2 mL) and the solid residue was filtered off through a pad of Celite®. The volatile organics were evaporated in vacuo and the crude residue was purified by silica gel column chromatography to obtain desired hemiacetals.Example 2: Deprotection of Pent-4-ene-l-ol Glycosides:

[0048] The pent-4-enyl glycoside (1.0 mmol) was dissolved in a mixture of solvents CH2C12 / CH3CN / H2O (5.0:3.0:0.5) and the reaction mixture was cooled to -10 °C. After 15 min, NIS (2.2 mmol) and TfOH (0.2 mmol) were added to the reaction mixture simultaneously and the reaction was stirred for 1 h at 00C. After completion, the reaction mixture was quenched with NaHCO3 solution and diluted with CH2C12. The organic layer was successively washed with water (2x25 mL), brine solution (1x25 mL), dried over anhydrous Na2SO4, filtered and the filtrate was concentrated in vacuo to obtain a crude residue that was purified by silica gel column chromatography using ethyl acetate and hexane to furnish corresponding hemiacetals.Example 3: Synthesis of Ethynyl Cyclohexyl Glycosyl Carbonate Donors

[0049] To a solution of hemiacetal (1.0 mmol) in anhydrous CH2C12 (5 mL), ethynyl cyclohexyl (4-nitrophenyl) carbonate S2 (1.2 mmol) and DMAP (1.1 mmol) were added and the reaction mixture was stirred at 25 °C for 5 h. the reaction mixture was concentrated andpurified by silica gel column chromatography (EtOAc / Hexane as mobile phase) to obtain ethynylcyclohexyl glycosyl carbonate donors.Example 4: Deprotection of the TBDPS-ethers:

[0050] To a solution of the silylated ether (1.0 mmol) in anhydrous pyridine and THF (4 m , 3: 1), HF«Py (3 mmol per TBDPS) was added at 0 °C and the reaction mixture was stirred at 25 °C for 3 h. After completion, the reaction mixture was quenched by the drop-wise addition of IN HC1 at 0 °C and diluted with 25 m of ethyl acetate. The organic layer was successively washed with 1 A HC1 (25 mb), saturated aqueous solution of NaHCO3 (25 mb) and brine solution (50 mb). The organic layer was dried over anhydrous Na2SO4 and concentrated in vacuo. The crude residue was purified by silica gel column chromatography using ethyl acetate and hexane to furnish corresponding alcohol.Example 5: Procedure for one-pot Glycan Editing methodology

[0051] To a solution of trisaccharide 5 (leq., 300 mg) in 3 mb of anhydrous CH2C12, BF3«OEt2 (3 eq, 74 ph) was added at 0 °C. After 10 min, reaction mixture was refluxed at 50 °C for 30 min. The reaction mixture was brought to 25 °C, 1 equivalent of glycosyl acceptor 6a-6e [6a (121mg), 6b (118 mg), 6c (100 mg), 6d (100 mg,), or 6e (167 mg)] were added to the reaction mixture and cooled to 0 °C. Freshly activated 4A MS powder (80mg) was added at 0 °C under nitrogen atmosphere and kept for vigorous stirring for another 15 min. Then NIS (1.5 eq, 66 mg), AgOTf (1.5 eq, 10 mg) were added simultaneously. The reaction mixture was stirred for 15 min at 0 °C and gradually warmed to 25 °C and stirred for 45 min. After this, chloro [tris(2, 4- ditbutylphenyl)phosphite]gold(I) ( 0.08 eq, 13 mg), AgOTf (0.1 eq, 5 mg) were added simultaneously to the reaction mixture and stirred for another 30 min. Et3N was added to quench the reaction mixture and the solvent was removed under reduced pressure. The crude residue was purified by silica gel column chromatography (30% - 40% ethyl acetate / hexane) to afford the compounds 11 a- I lf. Progress of the one-pot CIStERs was monitored by using semi-preparative HPEC system equipped with a normal phase silica gel diol column. Initially, mobile phase conditions were optimized by injecting the three standards samples 5, 6a, and 7 so that the peaks are well resolved for identification purpose. Subsequently, aliquots of CIStER reaction (1 la-1 If) were injected under above optimized mobile phase conditions. Products I la- I lf and intermediates during the CIStER were collected and characterized. Figure 1 depicts the liquid chromatography profile of CIStER of compounds 1 la- 1 If.

[0052] p-Tolyl-2,3,4-tri-0-benzyl-6-0-(2,3,4,6-tetra-0-benzoyl-a-D-glucopyranosyl)-l- thio-a / p-D-glucopyranoside (10):

[0053] This compound was synthesized from the trisaccharide 5 (Cut step of the CIStER) according to the one pot glycan editing methodology mentioned above (85% yield, white solid) (a :P = 5: 1). 1H NMR (400 MHz, CDC13): 5 8.02 - 7.81 (m, 8H), 7.53 - 7.21 (m, 29H), 7.07 (d, J = 8.5 Hz, 2H), 5.85 (t, J = 9.6, 2.7 Hz, 1H), 5.64 (t, J = 11.2, 8.5 Hz, 1H), 5.58 (d, 7 = 4.1 Hz, 1H), 4.91 (dd, J = 11.8, 3.1 Hz, 1H), 4.86 - 4.73 (m, 1H), 4.78 - 4.28 (m, 9H), 4.15 - 4.02 (m, 2H), 3.89 (dd, 7 = 10.9, 3.0 Hz, 1H), 3.76 (dt, 7 = 5.9, 3.0 Hz, 2H), 3.50 (d, 7 = 8.9 Hz, 1H), 2.31 (s, 3H); 13C NMR (101 MHz, CDC13): 5 166.3, 166.2, 165.9,165.9, 165.3, 165.3, 165.1, 165.1, 138.9, 138.8, 138.4, 138.2, 138.0, 137.8, 137.6, 137.2,133.5, 133.5, 133.2, 133.1, 132.4(2C), 130.5, 130.5, 130.2-129.9(32C), 129.7, 129.6, 129.4, 129.4, 129.2, 129.2, 128.7 -127.8(40C), 101.1, 101.1, 87.8, 87.4, 82.4, 80.7, 79.8, 77.4, 75.7,75.5 (2C), 75.0, 74.8(2C), 73.2(2C), 73.0(2C), 72.6(2C), 72.3(2C), 72.0, 71.9(2C), 70.7(2C),69.9, 68.1, 68.0, 63.4, 63.2, 21.3, 21.2; mp: 98 °C ; Optical Rotation: [a]D25 = +8° (c 0.26, CHC13) ; IR (cm-1, CHC13): 2990, 1728, 1265, 1215, 1108, 1027, 903, 742, 708, 666; HRMS (MALDI-TOF) [M+Na]+ m / z calculated for C68H62O14S 1158.3791 found 1158.3785.

[0054] Methyl-2, 3, 6-tri-0-benzoyl-4-0-(2-0-benzoyl 3,4-di-O-benzyl 6-O-(2,3,4-tri-O- benzyl-6-0-(2,3,4,6-tetra-0-benzoyl-P-D-glucopyranosyl)-a-D- mannopyranosyl)-a-D- mannopyranosyl)-a-D-glucopyranoside (Ha)

[0055] This compound was synthesized according the one pot glycan editing procedure mentioned above (61% overall yield, white solid) (a :P = 2: 1). 1H NMR (400 MHz, CDC13): 5 8.11 - 7.69 (m, 16H), 7.50 - 7.13 (m, 49H), 6.13 (d, 7 = 9.9 Hz, 1H), 5.92 (t, 7 = 9.7 Hz, 1H), 5.67 (t, 7 = 9.7 Hz, 1H), 5.62 - 5.52 (m, 1H), 5.31 (s, 1H), 5.20 (s, 1H), 5.16 (s, 1H), 4.98 (d, 7 = 7.8 Hz, 1H), 4.92 (d, 7 = 13.0 Hz, 1H), 4.84 - 4.76 (m, 2H), 4.73 - 4.06 (m, 18H), 3.98 (d, 7 = 6.6 Hz, 2H), 3.90 - 3.74 (m, 4H), 3.68 (d, 7 = 8.3 Hz, 2H), 3.59 (t, 7 = 11.2 Hz, 1H), 3.37 (s, 3H); 13C NMR (101 MHz, CDC13): 5 166.3, 166.3, 166.3, 166.2, 166.1, 166.0, 166.0, 165.9, 165.9, 165.8, 165.7, 165.7, 165.3, 165.2, 165.1, 164.9, 138.8, 138.7,138.6, 138.5, 138.5, 138.4, 138.3, 138.3, 138.0, 137.9, 133.6 -133.0 (18C), 130.1- 129.7 (40C) , 129.5 (2C), 129.2 (2C), 129.1 (2C), 129.0 (2C), 129.0 (2C), 128.7-128.1 (40C), 128.0 (2C), 127.9 (2C), 127.8-127.4 (30C), 102.0, 101.5, 101.4, 100.5, 100.5, 98.1, 97.2, 96.9, 80.0 (2C), 78.0 (2C), 77.7 (2C) , 77.4 (2C), 75.5 (2C), 75.2 (2C), 74.9 (2C), 74.6 (2C), 73.9 (2C),73.6 (2C), 73.2 (2C), 72.7 (2C), 72.3 (2C), 72.2 (2C), 72.1 (2C), 72.1 (2C), 71.6 (2C), 71.5 (2C), 71.4 (2C), 71.2 (2C), 70.5 (2C), 69.9 (2C), 69.1 (2C), 68.8 (2C), 65.6 (2C), 63.7 (2C), 63.4(2C), 55.9, 55.6; mp: 99 °C; Optical Rotation: [a]D25 = 43° (c 0.20, CHC13); IR (cm-1,CHC13): 2921, 1722, 1452, 1263, 1092, 1067, 1026, 750, 707; HRMS (MALDI-TOF) [M+Na] + m / z calculated for C116H106O29Na 1986.675 found 1986.635.

[0056] Methyl-2,3,6-tri-O-benzoyl-4-O-(2,3,4-tri-O-benzyl-6-O-(2,3,4-tri-O-benzyl-6-O- (2,3,4,6-tetra-O-benzoyl-P-D-glucopyranosyl)-a-D-mannopyranosyl)-a / p-D-glucopyranosyl)- a-D-glucopyranoside (11b)

[0057] This compound was synthesized according the one pot glycan editing procedure mentioned above (65% overall yield, thick syrup) (a :P = 2: 1). 1H NMR (600 MHz, CDC13): 5 8.18 - 7.86 (m, 24H), 7.56 - 7.08 (m, 106H), 6.28 (t, J = 10.2 Hz, 1H), 6.00 (t, J = 9.6 Hz, 1H), 5.74 (t, J = 9.8 Hz, 1H), 5.61 (t, J = 8.9 Hz, 1H), 5.37 (dd, J = 10.3, 3.7 Hz, 1H), 5.22 (d, 7 = 3.7 Hz, 1H), 5.14 (dd, J = 11.9, 4.0 Hz, 1H), 5.08 (d, 7 = 8.2 Hz, 1H), 4.97 (d, 7= 11.3 Hz, 1H), 4.92 (d, 7 = 4.0 Hz, 2H), 4.89 (d, 7 = 6.3 Hz, 1H), 4.86 (d, 7= 10.4 Hz, 2H), 4.80 (d, 7 = 8.7 Hz, 5H), 4.76 - 4.39 (m, 24H), 4.39 - 4.23 (m, 7H), 4.23 - 4.17 (m, 2H), 4.14 (t, 7 = 11.0 Hz, 2H), 4.10 (d, 7 = 11.4 Hz, 2H), 3.96 (dd, 7 = 11.1, 7.8 Hz, 4H), 3.82 - 3.65 (m, 11H), 3.63 - 3.56 (m, 3H), 3.54 - 3.47 (m, 3H), 3.45 (s, 1H), 3.44 (s, 3H), 3.32 (t, 7 = 9.5 Hz, 2H), 3.24 - 3.14 (m, 3H); 13C NMR (151 MHz, CDC13): 5 166.3, 166.2, 166.1, 166.1,166.1, 166.0, 166.0, 165.9, 165.9, 165.7, 165.3, 165.2, 165.2, 165.1, 139.2, 138.8, 138.6,138.6, 138.5, 138.5, 138.4, 138.4, 138.3, 138.2, 138.2, 137.9, 133.4 - 133.0 (20C), 130.2- 129.6 (30C), 129.2 (2C), 129.1 (2C), 129.1 (2C), 129.0 (2C), 128.9 (2C), 128.9 (2C), 128.7 (2C), 128.6, 128.5 - 128.1 (50C), 127.8 - 127.4 (30C), 101.5, 101.3, 101.0, 100.9, 99.2, 97.9, 96.9, 96.8, 82.7, 81.5, 81.4, 79.6, 79.4, 79.2, 79.1, 76.4, 75.6, 75.3, 75.2, 74.8, 74.7, 74.6,74.2, 74.1, 73.5, 73.1, 73.0, 73.0, 72.7, 72.7, 72.5, 72.3, 72.3, 72.1 , 72.1, 72.1, 72.0, 71.9,71.8, 71.7, 71.7, 71.6, 71.6, 71.5, 71.2, 69.9, 69.8, 69.3, 69.0, 68.8, 68.6, 68.4, 68.1, 65.6,65.1, 63.8, 63.6, 63.4, 63.3, 55.4, 55.3; Optical Rotation: [a]D25 = + 47° (c 0.16 CHC13);IR (cm-1, CHC13): 2922, 1723, 1452, 1263, 1068, 1026, 749, 707; HRMS (MALDI-TOF) [M+Na]+ m / z calculated for Cl 16H108O28Na 1972.696 found 1972.028.

[0058] Methyl-2,3,6-tri-O-benzoyl-4-O-(2,3,-di-O-benzoyl-5-O-(2,3,4-tri-O-benzyl-6-O- (2,3,4,6-tetra-O-benzoyl-P-D-glucopyranosyl)-a / p-D-mannopyranosyl)-a-D- arabinofuranosyl)-a-D-glucopyranoside (11c):

[0059] This compound was synthesized according the one pot glycan editing procedure mentioned above. (68% overall yield, white solid), (a :P = 2: 1). 1H NMR (400 MHz, CDC13): 5 8.13 - 7.74 (m, 18H), 7.58 - 7.15 (m, 42H), 6.27 - 6.06 (m, 1H), 5.90 (t, J = 9.7 Hz, 1H), 5.76 - 5.59 (m, 2H), 5.54 (d, J = 7.5 Hz, 1H), 5.49 (d, J = 9.5 Hz, 1H), 5.40 (d, J = 8.2 Hz, 2H), 5.21 (d, J = 5.2 Hz, 1H), 5.17 (s, 1H), 4.88 (d, J = 7.6 Hz, 1H), 4.86 - 4.73 (m, 1H), 4.71 - 4.43 (m, 8H), 4.39 (d, J = 4.9 Hz, 1H), 4.33 (d, J = 11.6 Hz, 1H), 4.28 (d, J =11.2 Hz, 1H), 4.25 - 4.19 (m, 3H), 4.15 (d, J = 13.9 Hz, 1H), 3.90 (s, 1H), 3.74 (dd, J = 19.0,9.8 Hz, 4H), 3.61 (t, J = 9.7 Hz, 1H), 3.44 (s, 3H); 13C NMR (101 MHz, CDC13): 5 166.3,166.2, 166.1, 166.1, 166.1, 165.9, 165.7, 165.4, 165.4, 165.3, 165.3, 165.2, 165.2, 165.1, 164.9, 164.8, 164.7, 164.7, 138.7, 138.6, 138.6, 138.5, 138.1, 138.0, 133.5-132.8(200), 130.1- 129.5(20C), 129.4(2C), 129.3(2C), 129.2(2C), 129.1(2C), 128.9 (2C), 128.9(2C), 128.8(2C), 128.8(2C), 128.7(2C), 128.6-128. l(60C), 127.9-127.3(200), 107.8, 107.4, 101.7(20), 101.3, 98.2, 97.0(20), 83.3, 82.2(20), 82.1, 82.0, 80.2, 77.7, 77.3, 75.2, 74.8, 74.7, 74.5, 74.5, 74.2, 74.0, 73.0, 72.8, 72.4(40), 72.4, 72.3, 72.1, 71.9, 71.9, 71.6, 71.2, 71.1, 69.9(20), 69.6, 69.3, 68.9, 68.8, 68.8, 68.6, 66.1, 63.4 (2C), 63.3 (2C), 55.5, 55.5; mp: 111 °C; Optical Rotation: [a]D25 = + 34° (c 0.23 CHC13); IR (cm-1, CHC13): 3010 ,1727, 1268, 1215, 1095, 745, 708, 667; HRMS (MALDI-TOF) [M+Na]+ m / z calculated for C108H96O29Na 1880.596 found 1882.640.

[0060] Methyl-2, 3, 6-tri-O-benzoyl-4-O-(2, 3-di-O-benzoyl 5-O-(2,3,4-tri-O-benzyl-6-O- (2,3,4,6-tetra-O-benzoyl-[3-D-glucopyranosyl)-a-D- mannopyranosyl)-P-D-ribofuranosyl)-a- D-glucopyranoside (lid)

[0061] This compound was synthesized according the one pot glycan editing procedure mentioned above. (66% overall yield, white solid), (a :[3 = 4: 1)

[0062] 1H NMR (400 MHz, CDC13): 5 8.08 - 7.79 (m, 18H), 7.49 - 7.16 (m, 42H), 6.09 (t, J = 9.8 Hz, 1H), 5.91 (t, 7 = 9.7, 1H), 5.68 (dd, 7 = 11.7, 9.4 Hz, 1H), 5.61 - 5.52 (m, 2H), 5.45 (d, 7 = 4.9 Hz, 1H), 5.39 (d, 7 = 3.6 Hz, 1H), 5.20 (d, 7 = 3.6 Hz, 1H), 5.17 (d, 7 = 2.0 Hz, 1H), 4.95 (d, 7 = 4.4 Hz, 1H), 4.91 (d, 7 = 9.0 Hz, 1H), 4.86 (d, 7 = 6.3 Hz, 1H), 4.79 (d, 7 =6.9 Hz, 1H), 4.75 (d, 7 = 3.4 Hz, 1H), 4.71 (s, 1H), 4.69 - 4.44 (m, 7H), 4.37 (dd, 7 = 11.6,6.3, 1H), 4.27 - 4.08 (m, 5H), 4.05 - 3.98 (m, 1H), 3.94 - 3.84 (m, 1H), 3.82 - 3.69 (m, 2H),3.68 - 3.60 (m, 1H), 3.36 (s, 3H); 13C NMR (151 MHz, CDC13): 5 : 166.4, 166.3, 166.3,166.2, 166.1, 166.0, 166.0, 165.7, 165.5, 165.5, 165.4, 165.4, 165.3, 165.2, 165.1, 165.1,165.1, 165.1, 139.3, 139.3, 139.1, 138.9, 138.5, 138.4, 133.6 - 133.1 (20C), 130.1 -129.9(40C) , 129.4 (2C), 129.3 (2C), 129.2 (2C), 129.2 (2C), 129.1 (2C), 129.0 (2C), 129.0 (2C), 128.7 - 128.4 (40C), 128.2 (2C), 128.1 (2C), 127.9 - 127.4 (20C), 107.7, 106.7, 101.9, 101.7,101.6, 98.6, 97.2 (2C), 82.3, 81.9, 81.1, 80.4, 79.4, 78.6, 76.4, 76.0, 75.2, 75.2, 74.9, 74.9,74.6, 74.6, 74.5, 73.3, 73.2, 73.2, 73.0, 72.5, 72.4, 72.3, 72.1, 72.0, 71.9, 71.8, 71.8, 71.5,71.2, 70.3, 70.1, 70.0, 69.9, 69.3, 69.1, 68.7, 68.4, 66.7, 63.4, 63.4 , 63.0 (2C), 55.7 (2C); mp: 104 °C; Optical Rotation: [a]D25 = + 49° (c 0.17, CHC13); IR (cm-1, CHC13): 2942,1726, 1452, 1264, 1093, 1068, 1026, 747, 705, 666; HRMS (MALDI-TOF) [M+Na]+ m / z calculated for C108H96O29Na 1880.596 found 1879.900.

[0063] Methyl-2, 3, 6-tri-O-benzoyl-4-O-(2, 3-di-O-benzoyl 5-0- (2, 3-di-O-benzoyl 5-0 - (2,3,4-tri-O-benzyl-6-O-(2,3,4,6-tetra-O-benzoyl-P-D-glucopyranosyl)-a / p -D- mannopyranosyl)-a-D-arabinofuranosyl)-a-D-arabinofuranosyl)-a-D-glucopyranoside (lie)

[0064] This compound was synthesized according the one pot glycan editing procedure mentioned above. (64% overall yield, white solid), (a :P = 3: 1). 1H NMR (400 MHz, CDC13): 5 8.10 - 7.74 (m, 22H), 7.50 - 7.15 (m, 48H), 6.17 (t, J = 9.5 Hz, 1H), 5.88 (t, J = 9.7 Hz, 1H), 5.67 - 5.58 (m, 3H), 5.50 (s, 1H), 5.48 (s, 1H), 5.41 (s, 1H), 5.36 (d, J = 4.9 Hz, 1H), 5.19 (s, 2H), 5.08 (s, 1H), 4.88 (d, J = 8.1 Hz, 1H), 4.78 (d, J = 9.4 Hz, 1H), 4.74 - 4.44 (m, 9H), 4.35 (d, J = 11.4 Hz, 1H), 4.31 - 4.18 (m, 6H), 4.13 - 4.00 (m, 2H), 3.90 (s, 1H), 3.84 - 3.69 (m, 5H), 3.64 (d, J = 8.8 Hz, 1H), 3.45 (s, 3H); 13C NMR (101 MHz, CDC13): 5166.4, 166.3, 166.3, 166.2, 166.1, 165.9, 165.8, 165.7, 165.5, 165.5, 165.5, 165.4, 165.4, 165.3, 165.2, 165.2, 165.2, 165.1, 165.1, 164.9, 164.6, 138.5(2C), 138.5(2C), 138.4, 137.9, 133.5 - 132.7(20C), 130.0 - 129.6(30C), 129.5(2C), 129.5(2C), 129.4(2C), 129.4(2C), 129.4(2C), 129.2(2C), 129.2(2C), 129.1(2C), 128.9(2C), 128.9(2C), 128.8(2C), 128.6 - 128.1(50C), 127.8 -127.3(45C), 107.5, 107.4, 105.9, 105.9, 101.8(2C), 101.2, 98.2, 97.1(2C), 83.2, 83.2, 83.1, 82.0, 81.9, 81.8, 81.8, 81.7, 81.6, 80.2, 77.6, 76.9, 75.2, 74.7, 74.7, 74.4,74.4, 74.2, 73.6, 73.5, 73.0, 72.7, 72.5, 72.4(4C), 72.3(4C), 72.1, 71.9, 71.9, 71.7, 71.2, 71.2, 69.9, 69.4, 69.4, 68.6, 68.5, 68.5, 66.2, 65.6, 65.6, 63.3, 63.0, 55.5, 55.5; mp: 107 °C; Optical Rotation: [a]D25 = + 33° (c 0.18 ,CHC13); IR (cm-1, CHC13): 2922, 1724, 1452, 1268, 1096, 1027, 707; HRMS (MALDI-TOF) [M+Na]+ m / z calculated for C127H112O35Na 22219.688 found 2219.599.

[0065] Methyl-2,3,6-tri-O-benzoyl-4-O-(2,3,6-tri-O-benzyl-4-O-(2,3,4-tri-O-benzyl-6-O- (2,3,4,6-tetra-O-benzoyl-P-D-glucopyranosyl)-a-D-mannopyranosyl)-a / p-D-glucopyranosyl)- a-D-glucopyranoside (Ilf)

[0066] This compound was synthesized according the one pot glycan editing procedure mentioned above (70% overall yield, thick syrup) (a: P = 3: 1).

[0067] 1H NMR (600 MHz, CDC13) 5 8.12 - 7.78 (m, 14H), 7.42 - 7.18 (m, 51H), 5.98 - 5.77 (m, 1H), 5.74 - 5.65 (m, 1H), 5.61 - 5.49 (m, 1H), 5.33 - 5.27 (m, 1H), 5.17 (dd, J = 4.8, 3.0 Hz, 2H), 4.87 (dd, J = 11.6, 2.7 Hz, 2H), 4.84 - 4.81 (m, 2H), 4.60 - 4.36 (m, 13H), 4.26 - 4.11 (m, 6H), 4.09 - 4.01 (m, 2H), 3.83 - 3.71 (m, 6H), 3.66 - 3.58 (m, 3H), 3.45 (s, 3H). 13C NMR (151 MHz, CDC13) 5 166.3, 166.2, 166.2, 166.2, 166.1, 166.0, 165.9, 165.8,165.3, 165.3, 165.1, 165.0, 165.0, 165.0, 138.9, 138.8, 138.8, 138.7, 138.7, 138.6, 138.5,138.4, 138.3, 138.0, 138.0, 137.8, 133.4 - 133.0 (20C), 130.2-129.6 (30C), 129.2 (2C), 129.1 (2C), 129.1 (2C), 129.0 (2C), 128.9 (2C), 128.9 (2C), 128.7 (2C), 128.6, 128.5 - 128.1 (50C),127.8 - 127.4 (30C) 101.8, 101.7, 100.6, 99.7, 99.7, 98.6, 96.9, 96.9, 82.7, 81.5, 81.4, 79.6,79.4, 79.2, 79.1, 76.4, 75.6, 75.3, 75.2, 74.8, 74.7, 74.6, 74.2, 74.1, 73.5, 73.1, 73.0, 73.0,72.7, 72.7, 72.5, 72.3, 72.3, 72.1 , 72.1, 72.1, 72.0, 71.9, 71.8, 71.7, 71.7, 71.6, 71.6, 71.5,71.2, 69.9, 69.8, 69.3, 69.0, 68.8, 68.6, 68.4, 68.1, 65.6, 65.1, 63.8, 63.6, 63.4, 63.3, 55.4,55.3 Optical Rotation [a]D25 = + 46° (c 0.25, CHC13) IR (cm-1 CHC13): 3446, 2937, 1755, 1453, 1268, 1239, 1069, 1005, 895, 847, 749, 695 HRMS (MALDI-TOF) [M+Na]+ m / z calculated for Cl 16H108O28Na 1973.101 found 1973.321.Example 6: General Procedure for Cleaving of naturally occurring disaccharides

[0068] To a solution of per-O-benzylated disaccharides 12a-12d ( leq) in 4 mL of anhydrous CH2Q2, BF3«OEt2 (3 eq,) was added at 0 °C. After 10 min, reaction mixture was refluxed at 50 °C for Ihr. Et3N was added to quench the reaction mixture and the solvent was removed under reduced pressure. The crude residue was purified by silica gel column chromatography (10% - 20% ethyl acetate / hexane) to afford the compounds 13, 14, 15, and 16. Figure 2 depicts the liquid chromatography (LC) profile of CIStER of the compounds 13, 14, 15, and 16.Example 7: Procedure for one-pot Glycan Editing methodology

[0069] To a solution of disaccharide 17 (leq, 500 mg) in 4 mL of anhydrous CH2Q2, BF3«OEt2 (3 eq, 188 qL) was added at 0 °C. After 10 min, reaction mixture was refluxed at 50 °C for Ihr. The reaction mixture was brought to 25 °C, 1 equivalent of compounds 18a- 18c [18a (170mgmg), 18b (310mg), 18c (232 mg)] were added to the reaction mixture and cooled to 0 °C. Freshly activated 4A MS powder (80mg) was added at 0 °C under nitrogen atmosphere and kept for vigorous stirring for another 15 min. Then NIS (1.5 eq, 194 mg), AgOTf (0.25 eq, 36 mg) were added simultaneously. The reaction mixture was stirred for 15 min at 0 °C and gradually warmed to 25 °C and stirred for 45 min. After this, DIPEA (2eq, 164 qL), DMAP (0.5 eq, 29 mg) were added simultaneously to the reaction mixture and stirred for another 2 hr. After completion, the reaction mixture was concentrated under reduced pressure. The crude residue was purified by silica gel column chromatography (15% - 20% ethyl acetate / hexane) to afford the compounds 19a- 19c.

[0070] Methyl 2,3,6-tri-O-benzyl-4-O-(2,3,4,6-tetra-O-benzylglucopyranosyloxy hexanoyl)- a-D-glucopyranoside (19a):

[0071] This compound was synthesized according the one pot glycan editing procedure mentioned above (80% overall yield, thick syrup) (a: [3 = 2: 1). 1H NMR (400 MHz, CDC13): 5 7.37 - 7.13 (m, 35H), 5.03 - 4.74 (m, 9H), 4.70 - 4.61 (m, 2H), 4.58 (d, J = 3.3 Hz, 2H), 4.57 > 4.44 (m, 3H), 4.36 (d, J = 7.8 Hz, 1H), 4.26 (d, J = 3.3 Hz, 2H), 4.05 - 3.90 (m, 2H),3.81 (d, J = 9.9 Hz, 1H), 3.73 - 3.42 (m, 8H), 3.36 (s, 3H), 2.26 (td, J = 7.8, 3.0 Hz, 2H), 1.68 - 1.57 (m, 4H), 1.46 - 1.33 (m, 2H); 13C NMR (101 MHz, CDC13) 5 173.3, 173.3, 138.9,138.7, 138.6, 138.5, 138.4, 138.4, 138.3, 138.3, 138.2, 138.2, 138.1, 138.0, 137.9, 128.5,128.5, 128.5, 128.4, 128.4, 128.2, 128.1, 128.1, 128.0, 128.0, 128.0, 128.0, 127.9, 127.9,127.8, 127.8, 127.7, 127.7, 127.7, 127.7, 127.6, 127.6, 103.7, 98.0 (2C), 97.0, 84.8, 84.7,82.3, 82.1, 82.1, 82.0, 80.1, 80.0, 80.0, 77.9, 77.8, 77.6, 77.6, 75.9, 75.8, 75.7, 75.2, 75.1, 75.0, 75.0, 74.9, 74.8, 73.6, 73.5, 73.4, 73.4, 73.2, 70.2, 69.8, 69.8, 69.0, 68.7, 68.7, 68.6,67.9, 63.0, 62.9, 55.2, 55.2, 34.0, 29.5, 25.8, 24.7; Optical Rotation [a]D25 = +51° (c 0.25, CHC13); IR (cm-l CHC13): 3446, 2937, 1755, 1453, 1268, 1239, 1069, 1005, 895, 847, 749, 695; HRMS (Maldi-TOF) [M+Na]+ m / z calculated for C68H76O13Na : 1123.518 found 1123.824.

[0072] Methyl 2,3,6-tri-O-benzyl-4-O-(2S-((benzyloxy)carbonyl)amino-(3-(2,3,4,6-tetra-O- benzyl glucopyranosyloxy))propanoyl) a-D-glucopyranoside (19b)

[0073] This compound was synthesized according the one pot glycan editing procedure mentioned above (76% overall yield, thick syrup) (a: [3 = 2: 1). 1H NMR (400 MHz, CDC13): 5 7.36 - 7.18 (m, 40H), 6.09 (dd, J = 28.6, 8.7 Hz, 1H), 5.12 - 4.64 (m, 11H), 4.59 - 4.50 (m, 5H), 4.46 - 4.28 (m, 5H), 4.17 - 4.08 (m, 1H), 3.97 (td, J = 9.2, 2.7 Hz, 1H), 3.87 - 3.78 (m, 2H), 3.71 - 3.44 (m, 6H), 3.37 (d, J = 9.3 Hz, 1H), 3.30 (s, 3H), 3.27 - 3.20 (m, 1H); 13C NMR (101 MHz, CDC13): 5 170.0, 169.9, 156.3, 155.8, 139.0, 139.0, 138.8, 138.7, 138.6, 138.4, 138.4, 138.3, 138.3, 138.2, 138.1, 137.9, 137.9, 137.8, 136.3, 136.2-127.7 (96C), 104.1, 99.0, 98.1, 97.9, 84.5, 82.5, 82.2, 82.0, 81.8, 81.6, 80.3, 80.1, 79.8, 78.2, 78.0, 77.9, 76.0, 75.7, 75.5, 75.4, 75.1, 74.7, 73.8, 73.6, 73.4, 73.3, 72.9, 71.0, 70.5, 70.5, 70.3, 69.1,68.9, 68.7, 68.3, 68.3, 67.3, 67.2, 64.5, 64.4., 55.3, 55.4; Optical Rotation [a]D25 = +150(c 0.25, CHC13); IR (cm-l, CHC13): 3446, 2937, 1680, 1453, 1268, 1239, 1069, 1005, 895, 847, 749, 695; HRMS (MALDI-TOF) [M+Na]+ m / z calculated for C73H77O15NNa : 1230.519 found 1230.910

[0074] Methyl 2,3,6-tri-O-benzyl-4-O-((4R)-4-((3R,8R,9S,10S,13R,14S,17R)-3-(2,3,4,6- tetra-O-benzylglucopyranosyloxy)- 10,13 -dimethylhexadecahydro- 1H- cyclopenta[a]phenanthren-17-yl)pentanoyl) a-D-glucopyranoside (19c)

[0075] This compound was synthesized according the one pot glycan editing procedure mentioned above (78% overall yield, thick syrup) (a: [3 = 3: 1). 1H NMR (400 MHz, CDC13): 5 7.40 - 7.25 (m, 35H), 5.01 (d, J = 2.6 Hz, 1H), 4.99 - 4.62 (m, 11H), 4.60 (d, J = 1.2 Hz, 3H), 4.57 - 4.54 (m, 2H), 4.50 - 4.43 (m, 2H), 4.28 - 4.25 (m, 2H), 4.00 (td, J = 9.2, 3.5 Hz, 2H), 3.91 - 3.71 (m, 3H), 3.71 - 3.43 (m, 8H), 3.37 (s, 3H), 2.41 - 1.29 (m, 29H), 0.90 (s,6H), 0.61 (d, J = 2.8 Hz, 3H); 13C NMR (101 MHz, CDC13) 5 174.0, 174.0, 139.0, 138.7, 138.7, 138.6, 138.6, 138.3, 138.3, 138.3, 138.2, 138.1, 138.1, 138.0, 138.0, 137.9, 128.5- 127.6 (84C), 102.4, 98.1, 94.7, 85.0, 84.9, 82.5, 82.3, 82.2, 82.1, 80.3, 80.2, 80.0, 79.9, 78.1, 78.0, 77.6, 76.5, 76.0, 75.9, 75.9, 75.7, 75.1, 75.0, 75.0, 74.9, 73.5, 73.5, 73.4, 70.1, 70.0,69.3, 69.2, 68.7, 68.5, 68.4, 62.9, 62.8, 56.5, 56.4, 56.0, 55.3, 55.2, 42.9, 42.8, 42.2, 42.1,40.2, 40.0, 35.9, 35.9, 35.6, 35.3, 34.8, 34.7, 32.3, 32.0, 31.1, 30.9, 29.7, 29.7, 28.2, 27.4,27.4, 27.2, 26.4 , 24.2, 23.5, 23.3, 20.8, 20.8, 18.3, 18.3, 12.1, 12.1; Optical Rotation [a]D25= +39° (c 0.25, CHC13); IR (cm-1 CHC13): 3446, 2937, 1755, 1453, 1268, 1239, 1069, 1005, 895, 847, 749, 695; HRMS (MALDI-TOF) [M+Na]+ m / z calculated for C86H104O13Na : 1368.740 found 1368.028.Example 8: Gm scale One-pot synthesis of 6 '-galactosyllactose:P-D-galactopyranosyl-(l— >6)-P-D-galactopyranosyl-(l— >4)-o / p-D-glucopyranose (22):

[0076] To a solution of compound 20 (leq, 3gm) in 15 mL of anhydrous CH2C12, TfOH (3 eq, 390 pL) was added at 0 °C. After 10 min, reaction mixture was refluxed at 50 °C for Ihr. The reaction mixture was brought to 25 °C, 1 equivalent of compounds 21 (1.7gm) were added to the reaction mixture and cooled to 0 °C. Freshly activated 4A MS powder (lOOmg) was added at 0 °C under nitrogen atmosphere and kept for vigorous stirring for another 15 min. Then NIS (1.5 eq, 1.22 gm), AgOTf (0.25 eq, 232 mg) were added simultaneously. The reaction mixture was stirred for 15 min at 0 °C and gradually warmed to 25 °C and stirred for 45 min. After this to this reaction mixture chloro[tris(2,4-ditertbutylphenyl)phosphite] gold(I) ( 0.08 eq, 223mg) AgOTf (0.08eqv 65mg,) were added simultaneously to the reaction mixture and stirred for another 30 min. After this to this solution 15 ml of anhydrous MeOH was added and then NaOMe (3.3 eq, 1.34gm) was added and kept for stirring at 25 °C for 2hr. After completion (1 h) water (5 mL), Amberlite 120 H+ (4.5 g) were added and the reaction mixture was stirred for 30 min. Then it was concentrated in vacuum, co-evaporated with toluene, and lyophilized to yield 6'-galactosyllactose. (white foam, 1.4gm ,71% over 4 steps, a: P = 1:3). 1H NMR (600 MHz, Deuterium Oxide) 5 5.16 (d, J = 3.7 Hz, 1H),4.59 (d, J = 7.9 Hz, 1H), 4.44 - 4.34 (m, 4H), 4.19 - 4.03 (m, 2H), 4.01 - 3.29 (m, 37H), 3.23 - 3.12 (m, 1H). 13C NMR (151 MHz, D2O) 5 103.3 (2C), 103.3, 103.2, 96.0, 92.1, 81.0, 75.6, 75.1,74.9, 74.0, 73.9, 73.9, 72.7, 72.7, 72.5, 72.5, 71.4, 70.8, 70.7, 70.7, 70.4, 69.5, 69.5, 68.9,68.9, 68.9, 68.7, 68.6, 67.3, 61.0. mp: 185 °C Optical Rotation [a]D25 = + 160(c 0.23, H20 IR (cm-1 CHC13): 3446, 2937, 1453, 1268, 1239, 1069, 1005, 895, 847, 749, HRMS (ESIMS) [M+Na]+ m / z calculated for C18H32NaO16 : 527.1588 found 527.1583

[0077] Example 9: Procedure for one-pot Glycan Editing methodology

[0078] The trisaccharide 23 (300 mg, 0.266 mmol) was dissolved in 3mL of anhydrous CH2C12. The reaction vessel was cooled to 0 °C and BF3«OEt2 (98.7 pL, 0.799 mmol) was added. The reaction mixture was refluxed at 50 °C for 30 min, brought to 25 °C and external glycan acceptor (1 eq. for 24 0.5 eq. for 26) [24 (674 mg,) or 26 (323 mg)] were added to the reaction mixture and the reaction vessel was stirred at 0 °C. To this reaction mixture, freshly activated 4A MS powder (80 mg) was added at 0 °C under nitrogen atmosphere and kept for vigorous stirring for another 15 min. Then NIS (1.5 eq., 89 mg), AgOTf (0.2 eq., 13 mg) were added, simultaneously and stirred for 15 min at 0 °C and kept at 25 °C for another 45 min. After this to this reaction mixture, chloro [tris(2, 4 dir-butylphenyl)phosphite] gold(I) ( 0.08 eq., 14 mg), AgOTf ( 0.1 eq., 5 mg) were added simultaneously to the reaction mixture and stirred for another 30 min. Et3N was added to arrest the reaction and the solvent was removed under reduced pressure. The crude residue was purified by silica gel column chromatography (30% - 40% ethyl acetate / hexane) to afford the oligosaccharides 25 and 27. Figure 3 depicts the Profile of CIStER of compounds 23-27. Progress of the one-pot CIStERs was monitored by using semi-preparative HPLC system equipped with a normal phase silica gel diol column. Initially, mobile phase conditions were optimized by injecting the four standards samples 23, S27, 24, and 26 so that the peaks are well resolved for identification purpose. Subsequently, aliquots of CIStER reaction (14,16) were injected under above optimized mobile phase conditions. Products 25&27 and intermediates during the CIStER were collected and characterized.

[0079] Allyl-3,4,6-tri-O-benzyl-2-O-(2, 3 di-O-benzoyl -5-O-(2, 3-di-O-benzoyl-5-O-(2,3-di- O-benzoyl-5 -O-(2,3 -di-O-benzoyl-5 -O-(2,3 -di-O-benzoyl-5 -O-(2,3 -di-O-benzoyl-5 -O-(2,3 - di-O-benzoyl-5-O-(2,3,4-tri-O-benzyl-6-O-(2,3,4,6-tetra-O-benzoyl-a-D-mannopyranosyl)- a / p-D-mannopyranosyl)-a-D-arabinofiiranosyl)-a-D-arabinofiiranosyl)-a-D- arabinofiiranosyl)-a-D-arabinofuranosyl)-a-D-arabinofuranosyl)-a-D-arabinofiiranosyl)-a-D- arabinofiiranosyl)-a-D- Mannopyranoside (25))

[0080] This compound was synthesized according to above mentioned one pot glycan editing procedure (51% overall yield, white solid).

[0081] 1H NMR (600 MHz, CDC13): 5 8.15 - 7.75 (m, 36H), 7.57 - 7.14 (m, 84H), 6.11 (t, J = 10.1, 3.5 Hz, 1H), 5.97 (t, J = 10.2, 6.8, 3.3 Hz, 1H), 5.81 - 5.72 (m, 2H), 5.69 - 5.62 (m, 12H), 5.62 - 5.53 (m, 3H), 5.46 - 5.36 (m, 7H), 5.30 - 5.14 (m, 2H), 5.02 (t, J = 5.9 Hz, 2H), 4.86 (d, J = 10.8 Hz, 1H), 4.80 - 4.73 (m, 1H), 4.70 - 4.49 (m, 14H), 4.42 - 4.34 (m, 1H), 4.30 (d, J = 11.1 Hz, 2H), 4.25 - 4.13 (m, 10H), 4.12 - 4.02 (m, 2H), 4.02 - 3.81 (m, 16H),3.75 - 3.64 (m, 2H), 3.63 - 3.55 (m, 1H); 13C NMR (151 MHz, CDC13): 5 166.3- 165.1(36C), 138.7, 138.7, 138.7, 138.5, 138.5, 138.5, 138.5, 138.5, 138.4, 138.4, 138.2,138.1, 133.9(2C), 133.6 -133.0(40C), 130.1 - 129.8(80C), 129.7-129.2(36C), 128.6 - 128.1(80C), 128.0 - 127.5(40C), 117.3(2C), 108.5, 106.8, 106.2, 106.0-105.9(12C), 101.9, 98.5, 98.5, 98.0, 97.8, 82.7- 81.6(42C), 80.6, 80.1, 79.8, 78.0, 77.8, 75.3, 75.2(2C), 75.1, 75.0, 74.8(2C), 74.7(2C), 74.5, 74.2(2C), 73.9(2C), 73.6, 73.3, 72.7(2C), 72.2, 71.9, 71.9(2C), 71.7, 71.1, 70.6, 70.5, 70.2, 70.1, 69.6(2C), 68.9, 68.9, 68.0(2C), 67.0(2C), 66.9, 66.0(14C), 62.8(2C); mp: 97°C; Optical Rotation: [a]D25 = + 3° (c 0.15, CHC13); IR (cm- 1, CHC13): 2918, 1722, 1452, 1264, 1109, 1026, 708 ; HRMS (MALDI-TOF) [M+Na]+ m / z calculated for C224H200O62Na 3905.243 found 3905.878.

[0082] Allyl-3,4,6-tri-O-benzyl-2-O- (3, 5-di-O-(2, 3-di-O-benzoyl-5-O-(2,3-di-O-benzoyl-5- O-(2,3-di-O-benzoyl-5-O-(2,3,4,-tetra-O-benzyl-6-O-(2,3,4,6-tetra-O-benzoyl-a-D- mannopyranosyl)-a / p-D-mannopyranosyl)-a-D-arabinofuranosyl)-a-D-arabinofuranosyl)-a- D-arabinofuranosyl)-a-D-Mannopyranoside (27):

[0083] This compound was synthesized according to above mentioned one pot glycan editing procedure. (45% overall yield, white solid).

[0084] 1H NMR (600 MHz, CDC13): 5 8.14 - 7.80 (m, 44H), 7.61 - 7.11 (m, 111H), 6.10 (t, J = 10.2 Hz, 2H), 5.97 (d, J = 9.4 Hz, 2H), 5.77 (d, J = 18.9 Hz, 2H), 5.71 (s, 1H), 5.69 - 5.62 (m, 6H), 5.61 - 5.53 (m, 5H), 5.49 (dd, J = 15.0, 6.1 Hz, 2H), 5.40 (q, J = 9.4, 8.6 Hz, 3H), 5.30 (d, 7 = 8.9 Hz, 1H), 5.27 (d, J = 10.5 Hz, 1H), 5.21 (d, 7 = 5.2 Hz, 1H), 5.14 (d, 7 = 9.3 Hz, 1H), 5.04 - 5.00 (m, 3H), 4.97 - 4.91 (m, 1H), 4.82 (d, 7 = 10.7 Hz, 1H), 4.74 (dd, 7 = 23.4, 10.9 Hz, 4H), 4.68 - 4.40 (m, 20H), 4.36 (dd, 7 = 11.8, 7.8 Hz, 3H), 4.31 - 4.13 (m, 11H), 4.11 - 4.02 (m, 5H), 3.98 (m, 5H), 3.93 - 3.82 (m, 13H), 3.76 (d, 7 = 4.0 Hz, 1H), 3.63 - 3.55 (m, 1H); 13C NMR (151 MHz, CDC13): 5 166.3 (8C), 165.7 (8C), 165.6 (8C),165.5.165.4, 165.3 (8C), 165.1 (8C), 138.7, 138.7, 138.6, 138.5, 138.5 (4C), 138.5 (4C),138.4, 138.3, 138.1 (4C), 134.1, 134.0, 133.5, 133.5-133.0 (20C), 130.0-129.8 (120C), 129.7- 129.1 (44C), 128.6 -128.3 (120C), 128.0 -127.4 (50C), 117.3, 117.2, 106.2-106.0 (10C),105.3, 105.1, 101.9 (2C), 98.8, 98.6, 98.5, 98.0, 97.8, 97.8, 82.7-81.4 (24C), 80.6-80.1 (12C),78.1, 78.1, 78.0, 77.8, 75.3-75.0 (14C), 74.7-74.5 (16C), 74.2 (2C), 73.9, 73.5, 73.3 (4C),73.3, 72.7 (4C), 72.3 - 71.7 (8C), 71.1, 70.6 ,70.5 , 70.0, 69.7 (2C), 69.3 (2C), 68.9, 68.9, 67.9 (4C), 67.1, 67.0, 66.9, 66.8, 66.7 (4C), 65.9-65.5 (12C), 62.8, 62.8; mp: 100 °C; Optical Rotation: [a]D25 = -5° (c 0.11, CHC13); IR (cm-1, CHC13): 2925, 1722, 1452, 1263, 1107, 1027, 709. HRMS (MALDI-TOF) [M+Na]+ m / z calculated for C278H250O75Na 4813.247 found 4813.145.

[0085] A skilled artisan will appreciate that the quantity and type of each ingredient can be used in different combinations or singly. All such variations and combinations would be falling within the scope of present disclosure.

[0086] The foregoing examples are merely illustrative and are not to be taken as limitations upon the scope of the invention. Various changes and modifications to the disclosed embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the scope of the invention.

Claims

We Claim:

1. A process for synthesis of the glycoconjugates using a cut-insert stitch-editing reaction (CIStER), wherein the process comprises the steps of:(a) cutting an interglycosidic bond of saccharide compound in a regiospecific manner using pTolSH and BF3Et2O in a solvent to afford thiotolyl gentiobiose and monosaccharide;(b) inserting Janus glycosyl acceptor donor compounds with thiotolyl gentiobiose in presence of reagent NIS / AgOTf and solvent to obtain janus-saccharides compound; and(c) stitching the janus-saccharides compound obtained in step (b) with monosaccharide in presence of [Au] / [Ag] catalyst and solvent to obtain stitched product, glycoconjugates.

2. A process for synthesis of the glycoconjugates using a cut-insert stitch-editing reaction (CIStER), wherein the process comprises the steps of:(a) cutting an interglycosidic bond of trisaccharide compound (5) in a regiospecific manner using pTolSH and BF3Et2O in a solvent to afford thiotolyl gentiobiose (10) and monosaccharide (7);(b) inserting Janus glycosyl acceptor donor compounds (6) with thiotolyl gentiobiose (10) in presence of reagent NIS / AgOTf and solvent to obtain trisaccharides compound (8); and(c) stitching the trisaccharides compound (8) obtained in step (b) with monosaccharide (7) in presence of [Au] / [Ag] catalyst and solvent to obtain stitched product, tetra- and pentasaccharide, glycoconjugates (11).

3. The process as claimed in claim 1 or 2, wherein the solvent in step (a) is dichloromethane, CH3CN, CHC13, Toluene, or THF.

4. The process as claimed in claim 1 or 2, wherein the solvent in step (b) is dichloromethane, CH3CN, CHC13, Toluene, or THF.

5. The process as claimed in claim 1 or 2, wherein the solvent in step (c) is dichloromethane, CHC13, Toluene, or THF.

6. The process as claimed in claim 1 or 2, wherein the glycoconjugates are selected from the group consisting of:Methyl-2, 3, 6-tri-O-benzoyl-4-O-(2-O-benzoyl 3,4-di-O-benzyl 6-O-(2,3,4-tri-O-benzyl-6-O-(2,3,4,6-tetra-O-benzoyl-P-D-glucopyranosyl)-a-D- mannopyranosyl)-a-D- mannopyranosyl)-a-D-glucopyranoside (I la); Methyl-2,3,6-tri-O-benzoyl-4-O-(2,3,4-tri-O-benzyl-6-O-(2,3,4-tri-O-benzyl-6-O-(2,3,4,6- tetra-O-benzoyl-P-D-glucopyranosyl)-a-D-mannopyranosyl)-a / p-D-glucopyranosyl)-a-D- glucopyranoside (11b);Methyl-2,3,6-tri-O-benzoyl-4-O-(2,3,-di-O-benzoyl-5-O-(2,3,4-tri-O-benzyl-6-O-(2,3,4,6- tetra-O-benzoyl-P-D-glucopyranosyl)-a / p-D-mannopyranosyl)-a-D-arabinofuranosyl)-a-D- glucopyranoside (11c);Methyl-2, 3, 6-tri-O-benzoyl-4-O-(2, 3-di-O-benzoyl 5- -(2,3,4-tri- -benzyl-6-O-(2,3,4,6- tetra-O-benzoyl-P-D-glucopyranosyl)-a-D- mannopyranosyl)-P-D-ribo furanosyl)-a-D- glucopyranoside (l id);Methyl-2, 3, 6-tri-O-benzoyl-4-O-(2, 3-di-O-benzoyl 5-0- (2, 3-di-O-benzoyl 5-0 -(2,3,4-tri-O-benzyl-6-O-(2,3,4,6-tetra-O-benzoyl-P-D-glucopyranosyl)-a / p -D-manno pyranosyl)-a-D- arabinofuranosyl)-a-D-arabinofuranosyl)-a-D-glucopyranoside (1 le);Methyl-2, 3, 6-tri-O-benzoyl-4-O-(2, 3, 6-tri-O-benzyl-4-O-(2, 3, 4-tri- -benzyl-6-O-(2, 3,4,6- tetra-O-benzoyl-P-D-glucopyranosyl)-a-D-mannopyranosyl)-a / p-D-glucopyranosyl)-a-D- glucopyranoside (I lf);Methyl 2,3,6-tri-O-benzyl-4-O-(2,3,4,6-tetra-O-benzylglucopyranosyloxyhexanoyl)-a-D- glucopyranoside (19a);Methyl 2,3,6-tri-O-benzyl-4-O-(2S-((benzyloxy)carbonyl)amino-(3-(2,3,4,6-tetra-O-benzyl glucopyranosyloxy))propanoyl) a-D-glucopyranoside (19b);Methyl 2,3,6-tri-O-benzyl-4-O-((42?)-4-((32?,82?,95,105,132?,145,172?)-3-(2,3,4,6-tetra-O- benzylglucopyranosyloxy)- 10,13 -dimethylhexadecahydro- lH-cyclopenta[a]phenanthren- 17- yl)pentanoyl) a-D-glucopyranoside (19c);P-D-galactopyranosyl-(1^6)-p-D-galactopyranosyl-(1^4)-a / p-D-glucopyranose (22);Allyl-3,4,6-tri- -benzyl-2- -(2, 3 di-O-benzoyl -5- -(2, 3-di-O-benzoyl-5-O-(2,3-di-O- benzoyl-5-O-(2,3-di-O-benzoyl-5-O-(2,3-di-O-benzoyl-5-O-(2,3-di-O-benzoyl-5-O-(2,3-di- O-benzoyl-5-O-(2,3,4-tri-O-benzyl-6-O-(2,3,4,6-tetra-O-benzoyl-a-D-mannopyranosyl)-a / p-D-mannopyranosyl)-a-D-arabinofuranosyl)-a-D-arabinofuranosyl)-a-D-arabinofuranosyl)-a-D-arabinofuranosyl)-a-D-arabinofuranosyl)-a-D-arabinofuranosyl)-a-D-arabinofuranosyl)-a- D- Mannopyranoside (25); andAllyl-3,4,6-tri- -benzyl-2- - (3, 5-di- -(2, 3-di-O-benzoyl-5-O-(2,3-di-O-benzoyl-5-O-(2,3- di-O-benzoyl-5-O-(2,3,4,-tetra-O-benzyl-6-O-(2,3,4,6-tetra-O-benzoyl-a-D-mannopyranosyl)-a / p-D-mannopyranosyl)-a-D-arabinofuranosyl)-a-D-arabinofuranosyl)-a- D-arabinofuranosyl)-a-D-Mannopyranoside (27).

7. The process as claimed in claim 1, wherein the saccharide in step (a) is disaccharide, trisaccharide, tetrasaccharide, pentasaccharide or hexasaccharide.

8. The process as claimed in claim 1 or 2, wherein the Ag / Au catalyst is chloro [tris(2, 4- ditbutylphenyl)phosphite] gold(I) / silver trifluoromethanesulfonate.

9. The process as claimed in claim 1 or 2, wherein the process is one-pot process.

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