Asymmetric Syntheses of (−)-8-<i>e</i><i>pi</i>-Swainsonine Triacetate and (+)-1,2-Di-<i>e</i><i>pi</i>-swainsonine. Carbonyl Addition Thwarted by an Unprecedented Aza-Pinacol Rearrangement
作者:Hossein Razavi、Robin Polt
DOI:10.1021/jo000527u
日期:2000.9.1
pyrrolidines 8a and 8b as advanced intermediates. Efficient protecting group manipulations converted pyrrolidines 8a and 8b to their corresponding partially protected analogues 10a and 10b, which upon Swern oxidation and diastereoselective Keck-type allylation with BF(3).Et(2)O afforded the required three-carbon homologues (10a, >20:1 de; 10b, 3.5:1 de). Use of the chelating Lewis acid MgBr(2) instead of BF(3)
从衍生自D-丝氨酸的O'Donnell Schiff碱酯1合成吲哚并核苷(-)-8-表-swainsonine三乙酸酯和(+)-1,2-二-表-swainsonine。(i)()Bu(5)Al(2)H / H(2)C = CHMgBr的1的还原烯基化,然后用OsO(4)对悬挂的烯丙基进行底物定向二羟基化,还原亚胺,和与Ph(3)P / CCl(4)环合得到多羟基吡咯烷8a和8b作为高级中间体。有效的保护基操作将吡咯烷8a和8b转化为其相应的部分受保护的类似物10a和10b,它们经Swern氧化和与BF(3)的非对映选择性Keck型烯丙基化.Et(2)O提供了所需的三碳同系物(10a, > 20:1 de; 10b,3.5:1 de)。使用螯合的路易斯酸MgBr(2)代替BF(3)。带有10a的Et(2)O导致aza碳上的新型氮杂频哪醇重排和烯丙基化,生成氨基醇17,这类似于吲哚izidin