Oligosaccharides armed-disarmed glycosylations

SCHEME 4.29 Oligosaccharide synthesis by armed-disarmed glycosylations. 

In the traditional approaches of oligosaccharide synthesis, the product of a glycosylation reaction had to be isolated and it required some chemical transformation(s) to make it suitable for the next glycosylation reaction. In some of the synthetic strategies described in Section 5.4, such as in the sequential glycosylations and in the armed-disarmed glycosylations, the product of one... 

Scheme 6 Oligosaccharide synthesis based on armed-disarmed glycosylation.

To synthesize longer oligosaccharide sequences using the armed-disarmed one-pot glycosylation approach, more than two consecutive glycosylation reactions are often... 

In later developments, the use of tin alkoxides of the acceptors to increase their nucleophilicity was introduced [591]. Danishefsky [592] expanded the use of IDCP-promoted reactions to oligosaccharide syntheses, showing that glycals are also amenable to armed-disarmed type glycosylations. 

Overall, the armed-disarmed strategy offers an efficient tool for the synthesis of oligosaccharides having a cis-trans glycosylation pattern.58,117 The synthesis of cis-cis-linked derivatives is also possible, but additional reprotection at the... 

The discovered cooperative effect was then applied to convergent synthesis of a variety of differently linked oligosaccharides (69). Amongst those, the activation of the armed 42 over a moderately (dis)armed 47 in the presence of Cu(0Tf)2 provided the disaccharide 48 in 64 % yield (Scheme 13). Subsequently, compound 48 was activated over a disarmed glycosyl acceptor 49... 

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