Glycosyl acceptor

Scheme 10 details the synthesis of A-ring glycosyl acceptor 19. The stereochemical relationship of 19 to D-fucose (21) is obvious. Peracetylation of D-fucose provides tetraacetate 58 in nearly quanti-... 

An alternative could be steric activation-deactivation at the anomeric centers of the donor and acceptor. An example using this concept is shown in Scheme 12. In the electronic activation-deactivation concept, deactivated p-nitrophenyl thioglycosides can, after functioning as glycosyl acceptors, be transformed into... 

Evidence for a glycosyl-enzyme intermediate of finite lifetime with inverting a-D-glycosidases, and details of its reaction, came from studies with 2,6-anhydro-l-deoxyhept-l-enitols and glycosyl fluorides. - Analysis of hydration and hydrolysis products on the one hand, and of glycosyla-tion products on the other, indicated an intermediate that could be approached by water from the yff-face only of the ring, and by other glycosyl acceptors only from the a-face (see Schemes 4 and 5 This can be considered a proof of the principle of microscopic reversibility of chemical reactions. 

Representative Procedure for Silicon Promoted Glycosylation with Cl-Hemiacetal Donors Using Me3SiBr and CoBr2 129 Representative Procedure for Mitsunobu-Type Glycosylation with Cl-Hemiacetal Donors and Phenol Glycosyl Acceptors 129 Representative Procedure for Appel-Type Glycosylation with Cl-Hemiacetal Donors 129... 

The schematic outline of the stepwise selective activation is shown in Scheme 1.9 thus, a glycosyl donor, bearing a reactive LGa, is coupled with a glycosyl acceptor,... 

According to the two-stage activation (or preactivation) approach, both glycosyl donor and glycosyl acceptor initially bear the same type of a leaving group (LGa). 

SnCI2-AgX The L-fucosyl fluoride derivative 18 reacts with glycosyl acceptor 19 in the presence of SnCl2-AgC104 to give the corresponding disaccharide 20 as a-anomer only (Scheme 2.7) [84],... 

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