Synthesis And Characterization Of L-arabinal

Glycals are the most important type of unsaturated monosaccharide derivatives, glycals as reactive intermediates have been playing a very important role in drug synthesis and organic reaction.In this thesis, We used three methods, one-pot, zinc and acetic acid, zinc powder and ammonium chloride synthesis of 3,4-di-O-acetyl-L- arabinal from L-arabinose through the reaction of reduction-elimination, and then removal of two acetyl group from 3,4 - di-O-acetyl-L-arabinal to obtain L-arabinal. When 3,4-di-O-acetyl-L-arabinal was synthesized using zinc powder and acetic acid,the influences of the reaction temperature, reaction time, the amount of zinc powder and acetic acid were sutdied through the orthogonal experimental design to get the better conditions of the reaction. The first synthesis of 3,4-di-O-acetyl-L-arabinal using ammonium chloride instead of acetic acid, and the reaction temperature, reaction time, ratio of raw materials and the amount of catalyst was discussed to determine the best conditions the reaction. The better reaction conditions are as follows:0.1mol 1-Br-2,3,4-tri-O-acetyl-L-arabinose , n (glycosyl bromide) / n (Zn) / n (NH4Cl) = 1.0:8.0:16.0 (mol / mol), the catalyst dosage was 7.0g, at room temperature 20℃reaction time 25h, to give the glycal with the yield reaching up 85.6%. purity of product was obtained through this process with cheap raw materials, mild reaction conditions and easy to operate . High pure colorless liquid product obtained by vacuum distillation without using chromatography . 3,4-di-O-acetyl-L-arabinal solution in methanol under the catalysis of anhydrous potassium carbonate, the reaction mixture was stirred 20 minutes at 20℃, tracked by TLC.After washing with the mixed solvent of ether and petroleum ether ,we can get the white crystal of L-arabinal ,and the total yield was 91.3%. At the same time, in the foundation of synthesizes the di-O-acetyl-L- arabinal, tri-O-acetyl-D-glucal, tri-O-acetyl-D-galactal, di-O-acetyl-D-xylal have aslo been successfully synthesized.