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Carbohydrates and glycoconjugates play key roles in crucial biological processes. Efficient strategies for the synthesis of complex oligosaccharides have been developed in which most of the synthetic effort is directed towards the preparation of saccharide building blocks that can be assembled into complex structures using a minimal number of synthetic steps. In a linear glycosylation strategy, a glycosylation product is converted to either a glycosyl donor by introducing a leaving group at the anomeric position, or a glycosyl acceptor by selective deprotection on the desired hydroxy group. Eliminating these tedious processes should lead to a strategy for the rapid synthesis of oligosaccharides.
One-pot glycosylation is a simple method for sequential glycosyl-bond formation carried out in the same flask. There are two ways.
1. Utilizing the difference in reactivity influenced by glycosyl donors (1)
D. Kahne et al. reported that the glycosylation of monosaccharides 1, 2, and 3 takes place in a sequential manner with 4-methoxyphenyl sulfoxide 2 activating faster than phenyl sulfoxide 1 and C-4 alcohol 3 reacting faster than C-4 silyl ether 2. The desired cyclamycin trisaccharide 5 produced in the one-pot reaction has an anomeric phenyl sulfide, which can be used for the following formation of a glycosyl linkage. This has resulted in a dramatic saving of time and labor (less than 3 h from monosaccharides to purified trisaccharide).
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References |
(1) |
S, Raghavan, D, Kahne, J. Am. Chem. Soc. 115, 1580-1581, 1993 |
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(2) |
Z, Zhang, IR, Ollmann, X-S, Ye, R, Wischnat, T, Baasov, C-H, Wong, J. Am. Chem. Soc. 121, 734-753, 1999 and references therein.
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(3) |
H, Yamada, T, Harada, H, Miyazaki, T, Takahashi, Tetrahedron Lett. 35, 3979, 1994; H, Yamada, T, Kato, T, Takahashi, Tetrahedron Lett. 40, 4581, 1999
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