克拉屈滨EP杂质E

反应条件: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

实验步骤: The synthesis of L-thioLyxofuranose and D-thioRibofuranose was carried out in 7 steps from D-ribose and L-lyxose respectively with 29 and 21% yield respectively. This synthesis is illustrated in Scheme 6. ##STR27## The synthesis in order to obtain the thio-D-ribofuranose uses L-lyxose as starting product as in the Whistler synthesis (page 19). This strategy is called strategy C1-C4. Indeed, the sulfur atom is first introduced in the anomeric position and an NS2 nucleophilic substitution between the sulfur atom carried by the anomeric carbon (C1) and the C4 carbon carrying an OH activated by a Mesyl (Ms) group is then carried out. This strategy applied to the synthesis of 4-thio-D-ribofuranose and 4-thio-L-lyxofuranose resembles that which Walker used to obtain the 2-deoxy-D-ribofuranose series (Patent Eur. Pat. 0421 777 A 1 page 6). For example, WALKER's product 5 (Scheme 5) is similar to our product 10 (Scheme 6) in L-lyxofuranose series. ##STR28## The synthesis of the thionucleosides of uracil, thymine and cytosine was carried out using bis-trimethylsilyl acetamide (BSA) as silylating agent and trimethylsilyl trifluoromethanesulfonate (TMSTf) as coupling agent. The O and β nucleosides were obtained with 74, 77 and 70% yields respectively. The synthesis of the thionucleosides of adenine was carried out with SnCl4 in acetonitrile. The O and β nucleosides are obtained with 58% yield (Scheme 7). as in the Whistler synthesis (page 19) Indeed, the sulfur atom is first introduced in the anomeric position