On the use of 3,5-O-benzylidene and 3,5-O-(di-tert-butylsilylene)-2-O-benzylarabinothiofuranosides and their sulfoxides as glycosyl donors for the synthesis of β-arabinofuranosides:: Importance of the activation method
On the use of 3,5-O-benzylidene and 3,5-O-(di-tert-butylsilylene)-2-O-benzylarabinothiofuranosides and their sulfoxides as glycosyl donors for the synthesis of β-arabinofuranosides:: Importance of the activation method
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DOI：
10.1021/jo061440x
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发表时间：
2007-03-02
影响因子：
3.6
通讯作者：
Wink, Donald J.
中科院分区：
文献类型：
--
作者：
Crich, David;Pedersen, Christian Marcus;Wink, Donald J.
在碱性条件下，二醇与二溴甲苯反应得到了2- o -苄基-3,5- o -苄基- α -d -硫代阿拉伯糖醛酸苷。在-55℃与二氯甲烷中的1-苯亚砜基哌啶或二苯基亚砜和三氟甲烷磺酸酐活化后，与糖基受体的反应产生选择性很小或没有选择性的异头化合物混合物。类似的2- o -苄基-3,5- o -（二叔丁基硅烯）- α - d -硫代阿拉伯糖脲苷在1-苯基亚砜或二苯基亚砜条件下也没有明显的选择性。在n -碘琥珀酰亚胺和三氟甲磺酸银的作用下，硅炔缩醛表现出中等至高的选择性，与起始巯基糖苷的构型无关。在三氟甲烷磺酸酐的活化下，2- o -苄基-3,5- o -（二叔丁基硅烯）- α -阿拉伯氨基呋喃基亚砜供体也获得了高选择性。n -碘琥珀酰亚胺/三氟甲磺酸银和亚砜方法获得的高选择性与常见中间体一致，最有可能是氧碳离子。通过低温核磁共振工作确定，1-苯基亚砜或二苯基亚砜和三氟甲烷磺酸酐活化巯基苷的选择性很差，这似乎是由于糖基供体形成复杂混合物的结果。
A 2-O-benzyl-3,5-O-benzylidene-alpha-D-thioarabinofuranoside was obtained by reaction of the corresponding diol with alpha,alpha-dibromotoluene under basic conditions. On activation with 1-benzenesulfinyl piperidine, or diphenyl sulfoxide, and trifluoromethanesulfonic anhydride in dichloromethane at -55 degrees C, reaction with glycosyl acceptors affords anomeric mixtures with little or no selectivity. The analogous 2-O-benzyl-3,5-O-(di-tert-butylsilylene)-alpha-D-thioarabinofuranoside also showed no significant selectivity under the 1-benzenesulfinyl piperidine or diphenyl sulfoxide conditions. With N-iodosuccinimide and silver trifluoromethanesulfonate the silylene acetal showed moderate to high beta-selectivity, independent of the configuration of the starting thioglycoside. High beta-selectivity was also obtained with a 2-O-benzyl-3,5-O-(di-tert-butylsilylene)-alpha-arabinofuranosyl sulfoxide donor on activation with trifluoromethanesulfonic anhydride. The high beta-selectivities obtained by the N-iodosuccinimide/silver trifluoromethanesulfonate and sulfoxide methods are consistent with a common intermediate, most likely to be the oxacarbenium ion. The poor selectivity observed on activation of the thioglycosides with the 1-benzenesulfinyl piperidine, or diphenyl sulfoxide, and trifluoromethanesulfonic anhydride methods appears to be the result of the formation of a complex mixture of glycosyl donors, as determined by low-temperature NMR work.