Direct conversion of 1-deoxy-1-nitroalditols to methyl glycofuranosides

Treatment of the sodium nitronate forms of 1-deoxy-1-nitrohexitols with methanolic sulfuric or hydrochloric acid at −30 °C leads to their regiospecific conversion to the corresponding methyl glycofuranosides. The reaction exhibits more pronounced stereoselectivity for 1-deoxy-1-nitroalditols with the 2,3-erythro configuration than with the 2,3-threo substrates and cis methyl glycofuranosides are the major products. The observed stereoselectivity indicates the lysis of the protonated aci-nitro form which is a two-step process consisting of nucleophilic addition to the protonated carbon-nitrogen double bond followed by the bimolecular nucleophilic substitution of the nitrogen-containing residue.