| Abstract
| - Two thiopyranoside analogues of GDP-sugars, GDP-5-thio-d-mannose (14) and GDP-5-thio-l-fucose(15), were synthesized. The syntheses included the phosphorylations of tetra-O-acetyl-5-thio-d-mannosyl bromide (4) and tri-O-benzoyl-l-fucosyl bromide (6) with silver dibenzyl phosphate,deprotection of the phosphate groups, and condensation of the deprotected phosphates with GMP-imidazolidate (13) in the presence of MgCl2. These GDP-sugar analogues were found to be donorsubstrates for α(1,2)mannosyltransferase and α(1,3)fucosyltransferase, affording a 5-thiomannose-containing disaccharide (18) and a 5-thiofucose-containing trisaccharide (21), respectively. Theconformation of the disaccharide analogue 18 was similar to that of its native counterpart by ROESY.These findings for GDP-5-thiosugars together with previous demonstrations of enzymatic transferfrom UDP-5-thiosugars will allow the production of panels of oligosaccharide analogues withhydrolase-resistant properties.
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