作者:Róbert Fischer、Alexandra Drucková、Lubor Fiera、Alfonz Rybár、Christian Hametner、MichaŠ K. Cyrański
DOI:10.1055/s-2002-32579
日期:——
New chiral nitrones 7 and 12, easily prepared from D-xylose by multistep synthetic routes, undergo regioselective 1,3-dipolar cycloadditions with N-vinylated bases (uracil, adenine) giving isoxazolidinyl nucleosides in good yields. Attack of the dipolarophile on the Z-configuration of the nitrone through exo and endo transition states from the si face of nitrone (C-1'/C-3 erythro) affords C-3/C-5 cis
新的手性硝酮 7 和 12 很容易通过多步合成路线从 D-木糖制备,与 N-乙烯基化碱基(尿嘧啶、腺嘌呤)进行区域选择性 1,3-偶极环加成,以良好的产率得到异恶唑烷基核苷。亲偶极体通过硝酮的 si 面(C-1'/C-3 erythro)的外向和内向过渡态对硝酮的 Z-构型的攻击提供 C-3/C-5 顺式(外向)和 C- 3/C-5 反式(内)异恶唑烷作为两种主要异构体。