Total synthesis of 1,5-dideoxy-1,5-iminoalditols

Enantiomerically pure 1,5-dideoxy-1,5-imino-D-glycero-D-allo-heptitol (10) has been synthesized in ca. 9% overall yield by utilizing 2,3-O-isopropylidene-D-glyceraldehyde-N-benzylimine (1) as a chiral source and 2-(trimethylsiloxy)furan (2) as a homologative reactant. The opening move was the preparation of properly protected seven-carbon butenolide 4, followed by diastereoselective anti, cis-dihydroxylation of the lactone double bond and furanose-to-azapyranose ring expansion. This generated a piperidine intermediate 7, the stereochemistry of which was secured by a single crystal X-ray analysis of its diacetate 9.