Synthesis of l-Rare Sugars from d-Sorbitol Using a TiO2 Photocatalyst

TiO2 photocatalytic reaction at ambient conditionpromotes an environmentally friendly and promising method to convertbiomass-derived compound to l-rare sugars. In recent years, l-rare sugars have been attractingattention,both as active compounds and useful building blocks for use in thepharmaceutical industry; however, these compounds have low naturalabundances and cannot be extracted from natural products. Therefore,it is necessary to convert widely available substrates, such as biomass-derivedcompounds, to produce rare sugars. In this study, we examined theproduction of l-rare sugars using a TiO2 photocatalyst. d-Sorbitol was treated with a TiO2 photocatalystunder light irradiation, and the products were identified as glucose,gulose, fructose, sorbose, arabinose, xylose, erythrose, threose,and glyceraldehyde using high-performance liquid chromatography, liquidchromatography-mass spectrometry, and proton nuclear magneticresonance spectroscopy. Furthermore, the production of the l-rare sugars, l-gulose and l-xylose, was confirmedby optical rotation measurements. Analysis of the product concentrationsas a function of time suggested that d-sorbitol undergoesa decarbonization reaction and C-C bond cleavage when treatedwith a TiO2 photocatalyst.