aldehyde 4 in the presence of CeCl(3). Synthesis of the lactone 3 relied on a novel approach by taking advantage of a radical cyclization of acyclic selenocarbonate 6. The three building blocks 4, 5a, and 6 were prepared stereoselectivly from D-galactose (7), 2,5-anhydro-D-mannitol (8), and L-rhamnose (9), respectively. A new and efficient method for desymmetrization of the C(2)-symmetrical compound 8 is
通过THP-THF片段2和末端
丁烯内酯3的
钯催化交叉偶联反应,可实现强大的抗肿瘤产
乙酸原素粘液素(1)的总合成。构建片段2的关键过程是螯合-在
乙二醛23a中控制
乙炔基氯化镁的添加,以及由此制得的烷基
锂与THP醛4的缩合。内酯3的合成通过利用无环
硒代
碳酸酯6的自由基环化而依赖于新方法。这三个结构单元4、5a和6是从
D-半乳糖(7),2,5-脱
水D立体选择性地制备的-
甘露醇(8)和
L-鼠李糖(9)。还介绍了一种新的高效的对称对称C(2)化合物8的方法。