Synthesis and conformational analysis of bicyclic sulfonium salts. Structures related to the glycosidase inhibitor australine |
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Authors: | Kumar Nag S Pinto B Mario |
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Affiliation: | Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6. |
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Abstract: | The syntheses of eight sulfonium compounds with structures related to the naturally occurring pyrrolizidine alkaloid, australine, in which the bridgehead nitrogen atom is replaced by a sulfonium ion, are described. The synthetic strategy relies on the intramolecular attack of a cyclic thioether across a terminal double bond in the presence of a suitable electrophile. We postulate that these compounds, having a permanent positive charge on the sulfur atom, will mimic the highly unstable oxacarbenium ion transition state in a glycosidase-catalyzed hydrolysis reaction. The conformational preferences of these compounds, based on analysis of 1H-1H vicinal coupling constants and 1D-NOESY data, are attributed to both steric and electrostatic interactions. These compounds will be used in the study of structure-activity relationships with glycosidase enzymes. |
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