Novel sequential solid-phase synthesis of N-linked glycopeptides from natural sources
作者:Ernst Meinjohanns、Morten Meldal、Hans Paulsen、Raymond A. Dwek、Klaus Bock
DOI:10.1039/a705528e
日期:——
In the present report a practical and versatile procedure for the solid-phase synthesis of N-linked glycopeptides from natural sources has been demonstrated. The approach is based on the mild hydrazinolysis procedure to release N-linked oligosaccharides in their intact unreduced form from the natural glycoproteins, e.g. fetuin and ribonuclease B and subsequent formation of the corresponding glycosylamines. Treatment of the reducing sugars 1–7 with a saturated solution of ammonium hydrogen carbonate in either water or dimethyl sulfoxide (DMSO) gives in almost quantitative yields the glycosylamines 8–14. Coupling of the unprotected glycosylamines 8–14 to the side-chain-activated aspartic acid derivative Fmoc-Asp(ODhbt)-OBut 16 affords the N-glycosylated asparagine derivatives 17–23. Subsequent acetylation of the carbohydrate hydroxy groups and cleavage of the tert-Bu ester by trifluoroacetic acid (TFA) treatment yields the glycosylated N-linked building blocks 31–37. The building blocks 31–37 are then incorporated into the multiple-column peptide-synthesis protocol of the glycopeptide T-cell epitope analogues 40–46 of the mouse haemoglobin-derived decapeptide Hb (67–76), VITAFNEGLK. The decapeptide sequence VITAFNEGLK binds well to the MHC Class II Ek molecule and is non-immunogenic in CBA/J mice. Syntheses of several natural and unnatural glycosylations, e.g. N-acetylglucosamine, N,N′-diacetylchitobiose, glucose, maltotriose, maltoheptose and di- and tri-antennary complex oligosaccharides on the decapeptide Hb (67–76) affording the N-linked glycopeptides 40–46 are described. The N-linked glycopeptides 40–46 have been fully characterised by 1D- and 2D-1H and 13C NMR spectroscopy and by ES-MS.
本报告展示了一种从天然来源固相合成 N-连接糖肽的实用且多功能的方法。该方法基于温和的肼解程序,以完整的未还原形式从天然糖蛋白(如胎盘素和核糖核酸酶 B)中释放出 N-连接寡糖,随后形成相应的糖基胺。用碳酸氢铵在水或二甲基亚砜(DMSO)中的饱和溶液处理还原糖 1-7,几乎可以得到定量的糖基胺 8-14。将未受保护的糖基胺 8-14 与侧链激活的天冬氨酸衍生物 Fmoc-Asp(ODhbt)-OBut 16 偶联,可得到 N-糖基化的天冬酰胺衍生物 17-23。随后通过三氟乙酸(TFA)处理对碳水化合物羟基进行乙酰化并裂解叔丁酯,可得到糖基化的 N-连接构筑模块 31-37。然后,将这些结构单元 31-37 加入小鼠血红蛋白衍生的十肽 Hb(67-76)VITAFNEGLK 的糖肽 T 细胞表位类似物 40-46 的多柱肽合成方案中。十肽序列 VITAFNEGLK 与 MHC II 类 Ek 分子结合良好,对 CBA/J 小鼠无免疫原性。本文介绍了在十肽 Hb(67-76)上进行几种天然和非天然糖基化,如 N-乙酰葡糖胺、N,N′-二乙酰壳寡糖、葡萄糖、麦芽三糖、麦芽庚糖以及二元和三元泛酰复合寡糖,从而得到 N-连接的糖肽 40-46。通过 1D- 和 2D-1H 和 13C NMR 光谱以及 ES-MS 对 N-连接的糖肽 40-46 进行了全面鉴定。