Golgi endomannosidase inhibitor, α-d-glucopyranosyl-(1→3)-1-deoxymannojirimycin: a five-step synthesis from maltulose and examples of N-modified derivatives

Acid-catalysed O-acetylation of d-maltulose furnished the corresponding per-O-acetylated fructopyranose derivative that, after in situ deprotection at O-2 by reaction with triphenylphosphane dibromide, gave open-chain 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl-(1→4)-1,3,5-tri-O-acetyl-6-bromo-6-deoxy-d-fructose. Standard deprotection employing sodium methoxide in methanol at −30 °C, followed by treatment of the resulting free 6-bromodeoxymaltulose with sodium azide in N,N-dimethylformamide, allowed access to 6-azidodeoxymaltulose. Hydrogenation over Pearlmanʹs catalyst, accompanied by intramolecular reductive amination, yielded the desired title compound. This route allows access to preparative quantities and to a range of novel analogues with improved biostability.