Thioglycosyl acceptor

Such a synthesis is shown in Scheme 4.18a, in which a glycosyl bromide is coupled with the thioglycosyl acceptor to afford a thioglycosyl disaccharide. The glycosyl bromide was obtained from the corresponding 1-thioglycoside by treatment with Br2. It was shown [222-224] that phenyl selenoglycosides can be selectively activated in the... 

In the same year, Takahashi and coworkers demonstrated that various glycosyl donors could be sequenced in a one-pot strategy namely, glycosyl bromides, fluorides, or trichloroace-timidates were first coupled with a thioglycosyl acceptor (33). 

Scheme 1 Active-latent strategy in oligosaccharide syntheses. EDG Electron-donating group EWG electron-withdrawing group. (A) Active thioglycosyl donor (B) latent thioglycosyl acceptor, (C) latent oligosaccharide transformable into an active form...

To complete the evaluation of the relative reactivities of disarmed-latent p-nitrophenyl thioglycosyl acceptors, glycosidation of p-nitrophenyl 2,3,4-tri-O-benzyl-l-thio-p-D-galactopyranoside 46 was examined using the acceptor 17. Consumption of acceptor 17 took place within 1 h and, similar to its reaction with 47, an anomeric mixture of disaccharide 48 was isolated (76% yield) as a 4 1 mixture of the a/p-anomers due to the nonparticipating effect of 2-O-benzyl ether. 

---