Modular Synthesis of 4-Aryl- and 4-Amino-Substituted Benzene <i>C</i>-2′-Deoxyribonucleosides
作者:Michal Hocek、Nicolas Joubert、Milan Urban、Radek Pohl
DOI:10.1055/s-2008-1067038
日期:——
A modular methodology for the syntheses of various 4-substituted-phenyl C-2′-deoxyribonucleosides has been developed. Coupling of toluoylated halogenose 1 with 4-bromophenylmagnesium bromide afforded the desired bis(toluoyl)-protected 1β-(4-bromophenyl)-1,2-dideoxyribofuranose 2a, which was deprotected under Zemplen conditions to give the unprotected 1β-(4-bromophenyl)-1,2-dideoxyribofuranose 3, and reprotected to give the bis(tert-butyldimethylsilyl)-protected 1β-(4-bromophenyl)-1,2-dideoxyribofuranose 4. Alternatively, addition of 1-lithio-4-bromobenzene on tert-butyldimethylsilyl-protected lactone 5, followed by reduction of the hemiketal 6, also gave bis(tert-butyldimethylsilyl)-protected bromophenyl nucleoside 4. Intermediates 2a and 4 were then subjected to a series of palladium-catalyzed cross-coupling reactions, aminations, and C-H activation to give 1β-[4-(aryl-, alkyl-, or amino)phenyl]-1,2-dideoxyribofuranoses 8a-n after deprotection. Finally, other types of 4-arylphenyl C-nucleosides 8o-u were prepared directly by aqueous-phase Suzuki cross-coupling reactions of unprotected 3 with boronic acids under microwave irradiation.
已开发出用于合成各种 4-取代-苯基 C-2'-脱氧核糖核苷的模块化方法。甲苯酰化卤糖 1 与 4-溴苯基溴化镁的偶联提供了所需的双(甲苯酰)保护的 1β-(4-溴苯基)-1,2-二脱氧呋喃核糖 2a,其在 Zemplen 条件下脱保护,得到未保护的 1β-(4-溴苯基) )-1,2-二脱氧呋喃核糖 3,并重新保护以得到双(叔丁基二甲基甲硅烷基)-保护的 1β-(4-溴苯基)-1,2-二脱氧呋喃核糖 4。或者,在叔上添加 1-锂-4-溴苯-丁基二甲基甲硅烷基保护的内酯5,随后还原半缩酮6,也得到双(叔丁基二甲基甲硅烷基)保护的溴苯基核苷4。然后中间体2a和4进行一系列钯催化的交叉偶联反应、胺化、和 C-H 活化以给出 1β-[4-(芳基-、烷基-或氨基)苯基]-1,2-二脱氧呋喃核糖 8a-n 脱保护后。最后,在微波辐射下,通过未保护的3与硼酸的水相Suzuki交叉偶联反应直接制备了其他类型的4-芳基苯基C-核苷8o-u。