Stereodirecting Effect of C3-Ester Groups on the Glycosylation Stereochemistry of L-Rhamnopyranose Thioglycoside Donors: Stereoselective Synthesis of α- and β-L-Rhamnopyranosides
Stereodirecting Effect of C3-Ester Groups on the Glycosylation Stereochemistry of L-Rhamnopyranose Thioglycoside Donors: Stereoselective Synthesis of α- and β-L-Rhamnopyranosides
复制标题
C3-酯基团对 L-吡喃鼠李糖硫代糖苷供体糖基化的立体定向作用：立体选择性合成 α- 和 β-L-吡喃鼠李糖苷
DOI：
10.1002/ejoc.201901186
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发表时间：
2019-10-09
影响因子：
2.8
通讯作者：
Yang, Jin-Song
中科院分区：
文献类型：
--
作者：
Lei, Jin-Cai;Ruan, Yu-Xiong;Yang, Jin-Song
描述了C3-酯基对L-吡喃鼠李糖（L-Rha）乙基硫代糖苷供体糖基化立体化学的调节作用。一方面，带有3-O-芳基羰基或乙酰丙酰基的L-Rha硫代糖苷供体经历高度α-选择性糖基化，以高化学产率提供各种各样的α-L-鼠李糖苷产物。另一方面，3-O-4-硝基吡啶甲酰基和2-吡嗪羰基取代的L-Rha硫代糖苷的糖基化显示β-立体选择性。当这些L-Rha供体与初级或反应性次级受体偶联时，仅获得或主要获得β异头产物，而当这些供体与反应性较低的仲醇反应时，β-选择性可能显著降低。新开发的α-和β-定向L-Rha供体1h和1 e的合成效用已通过结构独特的三糖9的有效合成得到证实，该三糖9来源于游泳球衣菌的细胞壁多糖。
The tuning effect of C3-ester groups on the glycosylation stereochemistry of L-rhamnopyranose (L-Rha) ethyl thioglycoside donors is described. On one hand, the L-Rha thioglycoside donors carrying 3-O-arylcarbonyl or levulinoyl group undergo highly alpha-selective glycosylation to afford a wide variety of alpha-L-rhamnoside products in high chemical yields. On the other hand, the glycosylation of the 3-O-4-nitropicoloyl and 2-pyrazinecarbonyl group substituted L-Rha thioglycosides displays beta-stereoselectivity. Only or predominant beta anomeric products are obtained when these L-Rha donors couple with the primary or reactive secondary acceptors, while the beta-selectivity may decrease significantly when these donors react with less reactive secondary alcohols. The synthetic utility of the newly developed alpha- and beta-directing L-Rha donors 1h and 1e has been demonstrated by the efficient synthesis of a structurally unique trisaccharide 9, which is derived from the cell wall polysaccharide of Sphaerotilus natans.