A convenient approach toward the synthesis of enantiopure isomers of DMDP and ADMDP

A practical method for the synthesis of five-membered iminocyclitols, pyrrolidine alkaloids bearing multiple hydroxyl substituents, has been developed. All of the eight key intermediates, enantiopure tri-O-benzyl cyclic nitrones, are prepared from four cheap, readily available d-aldopentoses. The nucleophilic addition of cyclic nitrones with vinyl magnesium chloride and TMSCN shows high 2,3-trans stereoselectivity. To construct the 2,3-cis configurations, inversion of the C-2 nitrile group is achieved via an elimination–reduction sequence. Using this approach, five isomers of DMDP and six isomers of ADMDP are prepared efficiently. In the biological evaluation, iminocyclitol 27 is a new and potent inhibitor against β-hexosaminidase with an IC50 value of 0.2 μM.