Synthesis and l-fucosidase inhibitory potency of a cyclic sugar imine and its pyrrolidine analogue

The synthesis of a fully deprotected ketimine-type iminosugar is reported, starting from commercial d-mannose diacetonide. An appropriate solvent system was critical for the success of the key tandem addition/cyclization reaction. Reduction of the imine was also achieved to yield the corresponding pyrrolidine in a stereoselective manner. The cyclic sugar imine displayed modest fucosidase inhibitory activity when compared to the saturated analogue.