The stereoselective reduction and cis-dihydroxylation of levoglucosenone (1,6-anhydro-3,4-dideoxy-beta-D-glycero-hex-3-enopyranos-2-ulose), gave D-allosan (1,6-anhydro-beta-D-allopyranose) in high yield.
The carbonyl group at the 2-position of levoglucosenone is reduced to obtain a hydroxyl group having a .beta.-configuration. The hydroxyl group having a .beta.-configuration is reversed to an .alpha.-configuration, and hydroxyl groups are added at the 3- and 4-positions in a cis-.alpha. form. Finally, the protective group of the hydroxyl group at the 2-position is eliminated. The reduction of the carbonyl group at the 2-position can be performed such that the levoglucosenone is reacted with aluminum lithium hydride or sodium boron hydride in an appropriate solvent. Reversion of the hydroxyl group having a .beta.-configuration can be performed by the Mitsunobu method or a method having a mesylation step and a step using cesium acetate. The addition of the hydroxyl groups to the 3-and 4-positions in the cis form can be performed by oxidizing the double bond across the 3- and 4-positions with an appropriate oxidizing agent. The elimination of the protective group of the hydroxyl group at the 2-position can be performed under basic conditions in accordance with normal methods. According to the method of the present invention, D-allosan can be obtained stereoselectively in high yield via a smaller number of steps than that of the conventional synthesis method.
A process for producing D-allosan (IV) from levoglucosenone (I) in a high yield, which comprises reducing the 2-carbonyl group of levoglucosenone, inverting the configuration of the resultant hydroxyl group from α to β, protecting it by acylation to give a compound (III), conducting α-cis addition of two hydroxyl groups to the double bond of the compound (III), and removing the protective group.
The stereoselective reduction and cis-dihydroxylation of levoglucosenone (1,6-anhydro-3,4-dideoxy-beta-D-glycero-hex-3-enopyranos-2-ulose), gave D-allosan (1,6-anhydro-beta-D-allopyranose) in high yield.