STEREOSPECIFIC SYNTHESIS OF NUCLEOSIDE ANALOGS

羟胺类化合物具有很高的立体选择性 给出几类具有生物学意义的分子，如 氨基糖和核苷的类似物。例如，高 羟胺的环加成反应具有立体选择性 无环？，？-不饱和酯的衍生物。加合物是 随后在温和的条件下环化，得到单一的异构体 易转化为醋酸酯保护的异恶唑烷-5-酮 异恶唑烷-5-醇。这些中间体和中间体的偶联 核苷碱基给出高顺式异恶唑烷基核苷 非金属络合物中罕见的选择性 2-脱氧呋喃糖基偶联反应3例。EI-MS、FAB-MS和Exact 已使用质量测量来表征这些产品。

Hydroxylamine derivatives are cyclized with high stereoselectivity to give several classes of biologically interesting molecules such as the analogs of aminosugar and nucleoside. For example, high stereoselectivity was observed in the cycloaddition of hydroxylamine derivatives to acyclic ?, ?-unsaturated esters. The adducts were subsequently cyclized under mild conditions to afford a single isomer of isoxazolidin-5-ones which was easily converted to acetate-protected isoxazolidin-5-ols. The coupling of these intermediates and nucleoside bases gave ?-isoxazolidinyl nucleosides with high cis selectivity which has rarely been observed in the nonmetal-chelated cases of 2-deoxyfuranosyl coupling reactions. EI-MS, FAB-MS and exact mass measurements have been used to characterize these products.