ACCESS TO FLUORESCENT-PROBES VIA ALLYL GLYCOSIDES - THE SYNTHESIS OF A BRUCELLA TRISACCHARIDE EPITOPE LINKED TO A COUMARIN

Oligosaccharide allyl glycosides are demonstrated to provide a route to fluorescent probes and simple inhibitors. Ethyl 2-O-acetyl-4-azido-3-O-benzoyl-4,6-dideoxy-1-thio-alpha-D-mannopyranoside (6) was used as glycosyl donor in the preparation of the trisaccharide [alpha-D-Rhap4NFo-(1 --> 2)-]2-alpha-D-Rhap4NFo-O-allyl (16). Thioglycoside 6 was activated with N-iodosuccinimide and triflic acid or by bromine in the glycosylations and the inhibitor 16 was obtained after deprotection by transesterification, reduction of the azido groups with hydrogen sulfide, and N-formylation with ethyl formate. Ozonolysis of the allyl glycoside in 16 and reductive amination with 7-amino-4-methylcoumarin then gave the target fluorescent trisaccharide conjugate.