The chemoenzymatic syntheses of thioanalogues of nodulation factors in which the nonreducing end glucosamine residue is available for the introduction of the fatty acid moiety at the free NH2group are reported. We are describing the chemical synthesis of UDP-GlcNH2and its use in the enzymatic transfer of GlcNH2by the bovine galactosyltransferase (EC 2.4.1.90) onto O-4 of the nonreducing end N-acetylglucosamine residues of chitobiose, thiochitobiose, and allyl thiochitobioside. The enzymatic reactions on chitobiose and thiochitobiose were followed by TLC and MALDI MS and showed about 50% conversion of the disaccharides to the desired products. However, these reducing trisaccharides could not be obtained totally free of salts and degraded on ion exchange chromatography. Thus, we investigated the enzymatic transfer on the nonreducing allyl thiochitobioside analogue. We describe here the chemical synthesis of this thiodisaccharide and the enzymatic transfer of GlcNH2at O-4 of its nonreducing end glucosamine residue to give the desired allyl thiotrisaccharide. This thiotrisaccharide was obtained pure in 41% yield and was characterized by1H NMR (HSQC) and HRMS.Key words: nodulation factors, synthesis, enzymatic transfer, thiooligosaccharides, UDP-glucosamine.
本研究报道了用化学酶法合成结瘤因子硫代类似物的过程,在这些类似物中,非还原端葡糖胺残基可用于在游离 NH2 基上引入脂肪酸分子。我们介绍了 UDP-GlcNH2 的化学合成及其在牛半乳糖基转移酶(EC 2.4.1.90)将 GlcNH2 酶促转移到壳寡糖、硫代壳寡糖和烯丙基硫代壳寡糖的非还原端 N-乙酰葡糖胺残基的 O-4 上的应用。利用 TLC 和 MALDI MS 对壳寡糖和硫代壳寡糖的酶促反应进行了跟踪,结果表明这些二糖约有 50% 转化为所需产物。然而,这些还原性三糖不能完全不含盐分,并在离子交换色谱中降解。因此,我们研究了非还原性烯丙基硫代几丁质类似物的酶促转移。我们在此描述了这种硫代二糖的化学合成及其非还原端氨基葡萄糖残基 O-4 上 GlcNH2 的酶促转移,从而得到所需的烯丙基硫代三糖。这种硫代异糖的纯度为 41%,并通过 1H NMR (HSQC) 和 HRMS 进行了表征。