Investigations of glycosylation reactions with 2-N-acetyl-2N,3O-oxazolidinone-protected glucosamine donors
Investigations of glycosylation reactions with 2-N-acetyl-2N,3O-oxazolidinone-protected glucosamine donors
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DOI：
10.1021/jo800971s
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发表时间：
2008-09-19
影响因子：
3.6
通讯作者：
Oscarson, Stefan
中科院分区：
文献类型：
--
作者：
Olsson, Johan D. M.;Eriksson, Lars;Oscarson, Stefan
NIS/ agotf促进与2,3- n， o-羰基-2-脱氧-1-硫- β -d -葡核苷供体的糖基化可以通过调节反应条件进行α -或β -选择性。少量的AgOTf（0.1当量）和较短的反应时间提供β -选择性，而0.4当量的AgOTf和较长的反应时间提供α -连接产物。核磁共振监测的糖基化和异构化实验表明，通过分子内机制（包括内环C - O键的裂解），β -键的初始形成仅为α -键。
NIS/AgOTf-promoted glycosylations with ethyl 2,3-N,O-carbonyl-2-deoxy-1-thio-beta-D-glueopyranoside donors can be performed with either alpha- or beta-selectivity by tuning the reaction conditions. Small amounts of AgOTf (0.1 equiv) and short reaction times give beta-selectivity, whereas 0.4 equiv of AgOTf and prolonged reaction times afford alpha-linked products. NMR-monitored glycosylation and anomerization experiments show initial formation of exclusively the beta-linkage, which anomerizes, through an intramolecular mechanism involving an endocyclic C - O bond cleavage, to the alpha-linkage.