Removal of Acyl Protective Groups from Glycopeptides: Base Does Not Epimerize Peptide Stereocenters, and beta-Elimination Is Slow.
Removal of Acyl Protective Groups from Glycopeptides: Base Does Not Epimerize Peptide Stereocenters, and beta-Elimination Is Slow.
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从糖肽中去除酰基保护基团：碱不会使肽立体中心差向异构化，β-消除速度缓慢。
DOI：
10.1021/jo951817r
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
J. Kihlberg
中科院分区：
文献类型：
--
作者：
P. Sjölin;M. Elofsson;J. Kihlberg
糖肽立体中心的差向异构化和β-消除被认为是糖肽脱酰化的重要潜在副反应，糖肽的碳水化合物部分被O-酰基保护。由于没有系统的调查，这些副反应已被报道，模型乙酰化，O-连接的糖三肽和它的三个差向异构体在α-碳立体中心的准备。在糖肽脱乙酰化常用的各种条件下，模型糖肽没有经历任何差向异构化（<1%）或β-消除，如通过（1）H NMR光谱测定的。在去除O-苯甲酰基所需的更严格条件下，β-消除发生缓慢，并伴有轻微（<5%）差向异构化。糖肽发生碱催化差向异构化和β-消除的惊人低趋势最可能是由于通过相邻酰胺基团的去质子化保护了α-碳立体中心。
Epimerization of glycopeptide stereocenters and beta-elimination have been considered as important potential side reactions on deacylation of glycopeptides which have the carbohydrate moieties protected with O-acyl groups. Since no systematic investigation of these side reactions has been reported, a model acetylated, O-linked glycotripeptide and its three epimers at the alpha-carbon stereocenters were prepared. The model glycopeptide did not undergo any epimerization (<1%) or beta-elimination, as determined by (1)H NMR spectroscopy, under various conditions which are in common use for deacetylation of glycopeptides. Under more severe conditions, which are required for removal of O-benzoyl groups, beta-elimination occurred slowly and was accompanied by slight (<5%) epimerization. The surprisingly low tendency of glycopeptides to undergo base catalyzed epimerization and beta-elimination is most likely due to protection of the alpha-carbon stereocenters by deprotonation of the adjacent amide groups.