Microwave assisted stereospecific synthesis of d-erythro-l-gluco-nonulose

A convenient, highly efficient synthesis of d-erythro-l-gluco-nonulose from a new 2-C-(hydroxymethyl) branched-chain aldose is presented. The nucleophilic addition of the appropriately protected aldose to formaldehyde afforded 2-C-(hydroxymethyl)-d-erythro-l-manno-octose. The branched sugar bearing a CH2OH group at C-2 provides access to a nine-carbon sugar in a single step through a stereospecific isomerization. The isomerization exploited the catalytic effect of molybdate ions and microwave irradiation. The structure of the product was analyzed by NMR spectra and quantum-chemical DFT calculations. DFT-computed proton-proton coupling constants were found to be comparable with the experimentally obtained coupling constants and agreed with the pyranose form of this branched-chain aldose.