Synthesis of Trisaccharides

3 Synthesis of Trisaccharides.- The considerable developments recently reported on the chemical synthesis of complex oligosaccharides (particularly those of biological importance) have been 

Biological studies have required the preparation of several 

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Studying the influence of the activator and using the MPEG-DOX-OH support (Scheme 4.18),12 the same group reported the synthesis of trisaccharide 79 using donors 76 and 78 both glycosylations were performed by action of 3 equiv of donor, in the presence of 0.1 equiv of dibutylboron triflate (DBBOTf) as activator and 4-A molecular sieves at -45°C for 30 min. 

Fucosyl phosphate 36 also very efficiently glycosylated the C4 position of acceptor 32. The orthogonality of the activating conditions of thioglycosides and glycosyl phosphate donors was exploited in the synthesis of trisaccharide glycal 41 (Scheme 6.7A).32 Furthermore, the different reactivity of a- and p-glycosyl phosphates was... 

In 1994, Takahashi and coworkers10 11 described another one-pot synthesis of trisaccharides using sequential additions of various glycoside donors and their corresponding activators.10 The first transformation relies on the activation of a... 

As an approach to the synthesis of trisaccharide 46, which corresponds to a repeating unit of the K antigen from E. coli LP 1092, the intermediate J , has also been glycosidated with the disaccharide halide 4 4 under the conditions given by Hanessian (35). 

T. Iversen and D. R. Bundle, Antigenic determinants of Salmonella serogroups and D,. Synthesis of trisaccharide glycosides for use as artificial antigens, Carbohydr. Res., 103 (1982) 29-40. 

Scheme 5. Synthesis of trisaccharide using glycosyl trichloroacetimidates and glycosyl phosphates.

SCHEME 6.6 One-pot synthesis of trisaccharide 33 using the super-armed building block 30. TBS, ferf-butyldimethylsilyl. 

SCHEME 6.8 Sulikowski s one-pot synthesis of trisaccharide 41. PMP, p-mcthoxyphenyl TES, triethylsilyl TMSOTf, trimethylsilyl triflate. 

SCHEME 6.11 Kobayashi s one-pot synthesis of trisaccharide 63 through chemoselective activation of glycosyl iV-trichloroacetylcarbamate. 

Displacement of the sulfonium ion by a hydroxy group of acceptor 83 in an SN2-like fashion resulted in the formation of the a-glycoside 84. This strategy was applied to the synthesis of trisaccharide 86 containing both a and p linkages in a one-pot fashion in 52% yield. 

SCHEME 6.20 Ito s stereoselective one-pot synthesis of trisaccharide 101. ClAc, chloroacetyl DTBMP, di-ferf-butylmethylpyridine. 

SCHEME 6.28 Mong s stereoselective one-pot synthesis using DMF as the novel additive to facilitate the 1,2-as-glycoside formation, (a) The glycosyl imidates formed with DMF. (b) The one-pot synthesis of trisaccharide 142. 

SCHEME 6.30 HC104-silica-promoted one-pot synthesis of trisaccharide 152. 

SCHEME 6.36 Mong s one-pot synthesis of trisaccharide 180 through combination of selective activation and armed-disarmed approach. 

Takeuchi, K, Tamura, T, Mukaiyama, T, Stereoselective glycosylation of thioglycosides promoted by respective combinations of A-iodo- or A-bromosuccinimide and trityl tetrakisfpentafluorophe-nyl)borate. Application to one-pot sequential synthesis of trisaccharide. Tetrahedron Lett., 124-125, 2000. 

Takahashi, T, Adachi, M, Matsuda, A, Doi, T, Comhinatorial synthesis of trisaccharides via solution-phase one-pot glycosylation. Tetrahedron Lett., 41, 2599-2603, 2000. 

Zhu, T, Boons, G J, A two-directional approach for the solid-phase synthesis of trisaccharide libraries, Angew. Chem. Int. Ed., 37, 1898-1900, 1998. 

In a related approach, Fraser-Reid and co-workers used Chiron s polystyrene-grafted crowns with Rich s photocleavable o-nitrobenzyl linker [140] and NPG donors in the synthesis of trisaccharide 277 (O Scheme 42) [141]. After attachment of the first aminoglucosyl moiety to... 

Isopropenyl glycosides could be activated selectively in the presence of armed NPGs, and that allowed a one-pot synthesis of trisaccharide 322 involving the successive glycosyl coupling of a vinyl glycoside jS-307, and an NPG, 321 (O Scheme 52). 

Synthesis of Trisaccharide 431, the Repeat Unit of the 0-Antigen Poiysaccharide from Danish Helicobacter pylori Strains... 

SCHEME 6. Synthesis of trisaccharide 18. Conditions (i) a-a-dimethoxytoluene, p-toluensulfonic acid,... 

The effectiveness of the glycal assembly approach to solid support oligosaccharide synthesis was impressively documented by on-resin analysis. The crude product of the multistep synthesis of trisaccharide 32 (Scheme 16) was monitored by high-resolution magic angle spinning NMR (HR-MAS) [70]. 

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