A　series　of　iso-allo-DNJ　and　L-isoDALDP　derivatives　were　synthesized　from　dithioacetal　16　with　sequential　and　highly　diastereoselective　Ho　and　Henry　reactions,　and　aziridinium　intermediate-mediated　ring　rearrangement　as　key　steps.　Glycosidase　inhibition　assay　found　four　of　them　as　selective　alpha-glucosidase　inhibitors,　and　the　less　substituted　compound　30　showed　more　potent　alpha-glucosidase　inhibition　(IC50　=　9.3　mu　M)　than　the　others.　Molecular　docking　study　revealed　different　docking　modes　of　the　iso-allo-DNJ　and　L-isoDALDP　derivatives　from　their　parent　compounds,　and　also　the　similarity　of　compound　30　to　isofagomine.