Iterative oligosaccharide synthesis

It was also found that introduction of any protecting group on the unprotected MOP glycosyl donors resulted in a significant decrease of the reactivity. This deactivation was considerable whenp-fluorobenzoates (FBz) were used as protecting groups, and it was applied to the synthesis of disaccharides, and to iterative oligosaccharide synthesis (O Scheme 80). 

Solution-phase oligosaccharide synthesis remains a slow process due to the need for iterative coupling and deprotection steps, with purification at each step along the way. To alleviate the need for repetitive purification events, solid-phase techniques have been developed.29,30 In solid-phase... 

Mereyala, H B, Reddy, G V, Directed, iterative, stereoselective synthesis of oligosaccharides by use of suitably 2-0-substituted 2-pyridyl 1-thioglycopyranosides on activation by methyl iodide. 

A solid-phase oligosaccharide synthesis based on the MOP donor/acceptor methodology was developed by Hanessian and co-workers [224]. Thus, an 0-unprotected polymer-phase bound MOP donor is coupled with an excess of a partially esterified MOP acceptor. Selective removal of the ester (or related protecting groups) from the new saccharides generates a new 0-unpro-tected MOP donor to engage in a subsequent iteration. 

S. Yamago, T. Yamada, O. Hara, H. Ito, Y. Mino, and J. Yoshida, A new, iterative strategy of oligosaccharide synthesis based on highly reactive /J-bromoglycosides derived from selenoglycosides, Org. Lett., 3 (2001) 3867-3870. 

Scheme 11.2-2 Automated oligosaccharide synthesis with glycosyl phosphates. Initial glycosylation of resin-bound acceptor produces a coupling product that may be subsequently deprotected. Iteration of coupling and deprotection cycles with phosphate donors 4-8 followed by cleavage of the resin-bound oligosaccharides and purification gives 1-3.

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