Synthesis Of Nucleoside Analogs By The Nucleophilic Addition Of Glycosyl-Nitrones

Nucleoside analogs which are similar with nucleosides indefinitely in the aspect of chemical structures can react with DNA and show very strong biological activities in antivirus and antitumor, and their synthesis is of the most importance nowadays.Based on the review of the nuleosides analogs synthesized from glycosyl-nitrones and the foundation of the study on the carbohydrate in our laboratory, a convienent method of the synthesis of nuleosides analogs through the nuleophilic addition of glycosyl-nitrones under the radiation of microwave was proposed. Two five-member glycosyl-nitrones transformed from arabinose and mannose were treated as intermediates to react with pyrrole, indole and pyrazolone respectively under the radiation of microwave to get the corresponding nucleophilic additional product. The Zn powder was chosen to cleave N-O bond in acid, and a series of nucleoside analogs were obtained after the deprotection. The structure of the compounds were determined by 1H-NMR,13C-NMR,2D-NMR and MS spectra. The factors involving in the stereoselectivity were explored:the steric hindrance of both the glycosyl-nitrones and electrophilic reagents can affect the stereoselectivity; the study showns that the more the steric hindrance is, the better the stereoselectivity is, the easier to form the trans diastereoisomers as the main additional products. In addition, the solvent plays the same important role in the stereoselectivity:the polar solvent THF and protonic polar solvent EtOH can control the reaction to get the transformed production in C-1 and C-2,3.