Rapid, one pot preparation of d-mannose and d-mannitol from starch: the effect of microwave irradiation and MoVI catalyst

The effect of microwave irradiation upon starch hydrolysis and simultaneous epimerization of the d-glucose to d-mannose obtained was investigated. An acidic aqueous solution of starch was treated with a catalytic amount of hexavalent molybdenum salt in microwave field and the composition of the reaction mixture was analyzed. Rapid starch hydrolysis and subsequent epimerization provided an equilibrium reaction mixture of d-glucose and d-mannose (2:1) without the formation of any undesirable by-products. The reduction of d-mannose with sodium borohydride yielded d-mannitol in very good yield. Microwave irradiation proved to be an efficient tool for the transformation of starch to mannose over an MoVI catalyst. This method has the advantages of environmental friendliness, easy operation, good yields and substantial reduction of reaction time.

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d-MannitolC6H14O6[α]D25=+23.7→+24.5 (c 10, 0.6 M aq Na2B4O7·10H2O)Source of chirality: d-mannoseAbsolute configuration: (2R,3R,4R,5R)-hexane-1,2,3,4,5,6-hexol