Stereocontrolled synthesis of enantiomeric imidazolopiperidinoses and imidazoloazepanoses using Wittig/dihydroxylation reactions

A new route for the synthesis of imidazolosugars—6-deoxyimidazolopiperidinoses 1 and 2 and 7-deoxyimidazoloazepanoses 3 and 4 in two enantiomerical forms—is reported. The new synthetic approach is based on two key reactions: (i) stereocontrolled Wittig Z-olefination of an imidazolecarbaldehyde with phosphoranes containing one chiral centre, obtained from (S)- and (R)-1,2,4-butantriol; (ii) diastereoselective cis-dihydroxylation of previously obtained olefins. All synthesised imidazolosugars were evaluated as potential inhibitors of glycosidases.