Syntheses of Racemic Diaminosugar Derivatives Starting from 1,2‐Dihydropyridines and from Nitrosobenzene

Racemic diaminosugars were easily obtained by a regio‐ and stereoselective three‐step synthetis. In the first step, regiospecific hetero‐ Diels ‐ Alder cycloadditions between 1,2‐dihydropyridines 1a and 10 and nitrosobenzene led to the bicyclic compounds 2a and 11 , respectively, cis ‐Glycol formation starting from these latter adducts, followed by hydrogenolysis of the NO bond and by exhaustive acetylation of the OH‐groups, led to the diaminolyxose 5 , the diaminomannose 14 and the diaminoallose 15 . When starting from benzyl 1,2‐dihydropyridine‐1‐carboxylate ( 1b ) and using the same reaction sequence, the racemic piperidine derivative 8 was obtained.