A Surprising Ring Opening Mechanism in the Formation of α-D-Arabinofuranosyl Nucleosides from 5-Substituted Uracils
作者:Per Trolle Jørgensen、Erik B. Pedersen、Claus Nielsen
DOI:10.1055/s-1992-26363
日期:——
Reaction of silylated 5-substituted uracil derivatives 6 with methyl 2,3,5-tri-O-benzoyl-α-D-arabinofuranoside (3) in the presence of trimethylsilyl trifluoromethanesulfonate afforded a mixture of the corresponding 5-substituted 1-(2,3,5-tri-O-benzoyl-α-D-arabinofuranosyl)uracils 7 and the acyclo 2,3,5-tri-O-benzoyl-1-O-methyl-1-(uracil-1-yl)-D-arabinitols 9 with the methoxy group intact at C-1. Compound 7 was deprotected with methanolic ammonia to give 8. Compound 7 was also reacted with Lawesson's Reagent to generate the corresponding 4-thio-α-D-arabinofuranoside nucleoside 14 which was deprotected by treatment with methanolic ammonia to give the nucleosides 15. Deprotected acyclo nucleosides 10 were likewise obtained from compounds 9. The mechanism for formation of the nucleosides 7 is discussed and the acyclo nucleosides 9 are believed to be intermediates.
在三甲基硅基三氟甲磺酸酯的存在下,硅烷化的5-取代尿嘧啶衍生物6与甲基2,3,5-三-O-苯甲酰基-α-D-阿拉伯呋喃糖苷(3)反应,生成相应的5-取代1-(2,3,5-三-O-苯甲酰基-α-D-阿拉伯呋喃糖基)尿嘧啶7和非环状的2,3,5-三-O-苯甲酰基-1-O-甲基-1-(尿嘧啶-1-基)-D-阿拉伯醇9的混合物,其中C-1位的甲氧基保持完整。化合物7通过与甲醇氨反应去保护,得到8。化合物7还与Lawesson试剂反应,生成相应的4-硫-α-D-阿拉伯呋喃糖核苷14,后者通过甲醇氨处理去保护,得到核苷15。从化合物9也得到了去保护的非环状核苷10。讨论了核苷7的形成机理,并且认为非环状核苷9是中间体。