Chemo-enzymatic synthesis of conformationally constrained oligosaccharides
Chemo-enzymatic synthesis of conformationally constrained oligosaccharides
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DOI：
10.1039/b308559g
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发表时间：
2003-01-01
影响因子：
3.2
通讯作者：
Boons, GJ
中科院分区：
文献类型：
--
作者：
Galan, MC;Venot, AP;Boons, GJ
n -乙酰乳胺衍生物4在C-6和C-2′之间有一个亚甲酰胺系链，用大鼠肝脏α -2,6-唾液基转移酶（ST6GalI）或重组人聚焦转移酶V （FucT-V）进行酶基化，分别得到构象受限的三糖5和6。亚甲基酰胺连接4的安装是通过两步程序进行的，其中包括用氯乙酸酐将LacNAc衍生物的C-6氨基功能酰化，然后用C-2'羟基亲核取代氯进行大环化。通过NOE和反式糖苷异核耦合常数测量和分子力学模拟确定了4的构象性质，这些研究确定了4的糖苷键是构象约束的，并且只存在于LacNAc可获得的几个能量最小值中的一个。转移到LacNAc和构象受限糖3和4的表观动力学参数表明，focusyltransferase V识别的是LacNAc的a-构象，而α -2,6-sialyltransferase识别的是LacNAc的b -构象。
N-Acetyllactosamine derivative 4, which has a methylene amide tether between C-6 and C-2', was enzymatically glycosylated using rat liver alpha-2,6-sialyltransferase (ST6GalI) or recombinant human fucosyltansferase V (FucT-V) to give conformationally constrained trisaccharides 5 and 6, respectively. The methylene amide linker of 4 was installed by a two-step procedure, which involved acylation of a C-6 amino function of a LacNAc derivative with chloroacetic anhydride followed by macrocyclization by nucleophilic displacement of the chloride by a C-2' hydroxyl. The conformational properties of 4 were determined by a combination of NOE and trans-glycosidic heteronuclear coupling constant measurements and molecular mechanics simulations and these studies established that the glycosidic linkage of 4 is conformationally constrained and resides in only one of the several energy minima accessible to LacNAc. The apparent kinetic parameters of transfer to LacNAc and conformationally constrained saccharides 3 and 4 indicates that fucosyltransferase V recognize LacNAc in its A-conformer whereas alpha-2,6-sialyltransferase recongizes the B-conformer of LacNAc.