作者:Jacob Ravn、Poul Nielsen
DOI:10.1039/b101364p
日期:——
The ring-closing metathesis method is applied in the construction of conformationally restricted bicyclic nucleosides. From diacetone-D-glucose, the unsaturated bicyclic carbohydrate derivative 11 is efficiently obtained through two vinyl group Grignard additions, subsequent metathesis of the double bonds, and resolution of the stereochemistry by an oxidation/reduction reaction sequence. Two separate routes differing in the 3-O-protecting group are compared. Thus, an additional protecting step improves the yields significantly. Standard conversions of 11 give the bicyclic nucleoside 22 containing an olefinic moiety with a high potential for further functionalisation. As examples, two simple bicyclic ribo-nucleoside analogues 4 and 5, which are restricted to the unusual South-type conformations, are synthesised.
环闭合转位法用于构建构象受限的双环核苷。从二乙酮-D-葡萄糖出发,经过两次烯基格林纳反应、后续双键的转位以及通过氧化/还原反应序列解决立体化学,成功合成了不饱和双环糖类衍生物11。比较了两条在3-O-保护基团上不同的合成路线。因此,额外的保护步骤显著提高了产率。将11进行标准转化,得到含有具有较高进一步功能化潜力的烯基部分的双环核苷22。作为示例,合成了两种简单的双环核糖核苷类似物4和5,这些类似物限制在不寻常的南型构象中。