1,2:5,6-Di-O-isopropylidene-D-hexofuranoses and their 3-keto derivatives

The synthesis of the only unknown 1,2:5,6-di-O-isopropylidene-D-hexose, D-mannose, is reported. Its preparation involved the stereospecific borohydride reduction of the 3-keto intermediate prepared from D-altrose. An improved synthesis of the known D-talose derivative proceeded in an analogous manner from the parent ketone. The four 3-keto derivatives of the diacetone D-hexoses were prepared and their properties compared. In an attempt to explain the differences found in the ease of hydration of these materials, high resolution infrared hydrogen bonding studies were carried out on the eight hexose derivatives and the one hydrated ketone.