The synthesis of D-psicose derivatives using recent oxidative procedures

Abstract

The oxidation of authentic 1,2,:4,5-di-O-cyclohexylidene-D-fructopyranose and of 1,2:4,5-di-O-isopropylidene-D-fructopyranose with dimethyl sulphoxide–acetic anhydride yields 1,2:4,5-di-O-cyclohexylidene-D-erythro-hex-3-ulopyranose and 1,2:4,5-di-O-isopropylidene-D-erythro-hex-3-ulopyranose, respectively. Reduction of the latter to 1,2:4,5-di-O-isopropylidene-D-psicopyranose was achieved with sodium borohydride (98·2% stereoselective) and with lithium aluminium hydride (90% stereoselective); this psicose derivative underwent rearrangement to the known di-O-isopropylidene-D-psicose. The formation of 1,2:4,5-di-O-cyclohexylidene-D-psicopyranose by the reduction of the appropriate 3-oxo-compound was found to be more highly steroselective. 1,2:5,6-Di-O-cyclohexylidene-α-D-glucofuranose was oxidised to 1,2:5,6-di-O-cyclohexylidene-α-D-ribo-hex-3-ulofuranose which was then reduced completely stereoselectively to 1,2:5,6-di-O-cyclohexylidene-α-D-allofuranose. All the 3-oxo-compounds were accompanied by substantial amounts (23–27%) of the corresponding 3-O-methylthiomethyl derivatives; in the case of 1,2:5,6-di-O-cyclohexylidene-3-O-methylthiomethyl-α-D-glucofuranose the configuration at C-3 was established from its n.m.r. spectrum.