Synthesis of 3-deoxyaldulosonic acid esters by one-carbon chain extension of glycal-derived lactone precursors

A convenient preparative route is described for 3-deoxyaldulosonic acids. Glycal precursors are oxidatively converted into 2-deoxyaldonolactones, which react with 1,3-dithian-2-yl anion to afford 1,3-propanediyl dithioacetals of higher 3-deoxyaldosuloses. Deprotection with mercuric salts in wet or dry alcohols gave high yields of the corresponding alkyl aldulosonates. Preparative reaction conditions were optimized and the anomeric configurations of the ketopyranose products were established by 13C NMR.