Selective synthesis of 1,6-anhydro-β-d-mannopyranose and -mannofuranose using microwave-assisted heating.

Abstract The dehydration of d -mannose and the demethanolization of methyl-α- d -mannopyranoside (MαMP) or methyl-α- d -mannofuranoside (MαMF) were examined using microwave-assisted heating for a 3-min irradiation at temperature from 120 to 280 °C in ordinary or dry sulfolane without any catalyst. The microwave-assisted heating of MαMP and MαMF smoothly proceeded to selectively afford the anhydromannoses, 1,6-anhydro-β- d -mannopyranose (AMP) and 1,6-anhydro-β- d -mannofuranose (AMF), respectively, in high yields. For MαMP in ordinary sulfolane at 240 °C, AMP was selectively obtained in the AMF:AMP ratio of 4:96, whereas AMF was the major product at the AMF:AMP ratio of 97:3 from MαMF in dry sulfolane at 220 °C.