Disaccharide donor

In a synthesis of a partial structure of the GPI anchor of Trypanosoma brucd, three of the four glycosylations were realized with the zirconocene activator (Cp2ZrCl2/AgC104, 1 1 Scheme 8.8). First, the coupling of a 1-D-myo-inositol acceptor with a disaccharide donor gave a mixture (93 %) of the desired a-linked trisaccharide and its (3-isomer in a ratio... 

Use of orthogonal activation strategies in the synthesis of a disaccharide donor. 

Glycosylation of MPEG-DOX-OH with 76 was achieved in 95% yield. After deacetylation using DBU in methanol, glycosylation using disaccharide donor 78 was performed and resin-linked trisaccharide was obtained in 85% yield. 

Scheme 9.14 The synthesis of a tetrasaccharide library (II). General design of library construction and monosaccharide donors are shown in part A. Disaccharide donors are constructed as shown in part B.

Iteration and sequential glycosidation in a stepwise manner or by block synthesis (e.g., disaccharide donor and disaccharide acceptor for tetrasaccharide synthesis)... 

This method has been successfully extended to the iterative synthesis of oligosaccharides. The disaccharides, derived from selective activations of unprotected MOP donors and partially esterified MOP acceptors, can be converted into reactive donors simply by deacylation. The newly generated unprotected MOP disaccharide donor can be subjected to another cycle of glycosylation by repeating the same process. Schemes 7 and 8 illustrate... 

Scheme 10 Synthesis of a sialyl Lex derivative using an MOP disaccharide donor.

To a solution of the glycosyl donor 13 (29 mg, 0.041 mmol) and the disaccharide donor 28 (16.8 mg 0.021 mmol) in dichloromethane (1.5 mL) was added activated powdered 4 A MS (30 mg). The solution was stirred at room temperature overnight nnder argon, and Cu(OTf)2 (30 mg 0.0826 mmol) was then added. Stirring was continued overnight (12 h), the reaction was quenched with a few drops of pyridine, the mixture was concentrated, and the residue was purified by flash chromatography on silica gel column with hexane-ethyl acetate-dichloromethane (2 I 0.5) to afford the title trisaccharide 29 (18.0 mg 60%). 

The disaccharide donors 55, 59, and 62 and the acceptors 53 and 57 were employed in the preparation of several oligosaccharides, including the octasaccha-rides 69-71 (Scheme 10.6) [33, 70], Further elaborated in Scheme 10.6 is the synthesis of compound 69—the most complicated of these structures—carrying the rare 3-O-sulfonation and several amino group functionalizations. The assembly of the... 

Wong and coworkers tested their reactivity-based one-pot synthesis protocol to assemble the sLex hexasaccharide [101]. As shown in Scheme 12.15, sequential regioselective glycosylation of the phthalimide-protected 3,4-diol 92 with the thiotolyl disaccharide donor 91 at 04 and the fucosyl donor 43 at 03, followed by coupling with the lactosyl 4 -alcohol 93 afforded the sLex hexasaccharide 94 in 42% overall yield and in a one-pot manner. The most elegant part in this synthesis was the application of the promoter combination that circumvents the adventitious formation of the... 

The disaccharide donor 31 was coupled to acceptor 27 to give tetrasaccharide 32. Deprotection of 28, 30 and 32 then gave two Haemophilus core structure oligosaccharides and an analogue thereof [9,52]. 

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