Neu5Ac衍生物和CMP-Neu5Ac衍生物高效合成技术的研究

Efficient and large-scale synthesis of N-acetyl neuraminic acid (Neu5Ac), CMP-Neu5Ac and their derivatives is very important because of the biological and pharmacological significance. The whole-cell catalysis is well studied and presents a new potential tool in industrial production of Neu5Ac. Convenient enzymatic synthesis of CMP-Neu5Ac is also recently well established by use of CMP-Neu5Ac synthase NeuA. However, the preparation of derivatives of Neu5Ac and CMP-Neu5Ac remains challenging due to their diverse and complex structures. Here we present an efficient synthetic strategy of the derivatives based on the combined use of the whole-cell catalysis and a chemoenzymatic approach. The proposed process contains (i) chemical modification of N-acetylglucosamine (GlcNAc) to produce a set of GlcNAc derivatives; (ii) whole-cell-catalyzed transformations of the Neu5Ac derivatives to Neu5Ac derivatives using a genetically engineered Escherichia coli strain we developed previously; and (iii) enzymatic preparation of the corresponding CMP-Neu5Ac derivatives from the GlcNAc derivatives by a recombinant NeuA overexpressed and purified from our another engineered E. coli strain. Our preliminary test have suggested that the whole-cell-catalyst as well as the recombinant NeuA exhibits a broad substrate tolerance, allowing successful transformations of GlcNAc derivatives, such as 6-F-GlcNAc and 6-Ac-GlcNAc, to the corresponding Neu5Ac and CMP-Neu5Ac derivatives. In this study, we will increase the possibility of the strategy to synthesize further derivatives with various substituents on gram-scale. Our study may generate sufficient and appropriate library compounds (natural and non-natural) for the future biological and pharmaceutical research.

N-乙酰神经氨酸（Neu5Ac）、CMP-Neu5Ac及其衍生物具有重要生物学意义和药物研究价值，如何快速、大量地制备这些化合物是唾液酸研究领域中的一个关键基础问题。全细胞催化是目前最具工业化生产潜力的Neu5Ac合成方法，酶法合成则代表着CMP-Neu5Ac的主流制备技术，而国内外关于它们衍生物制备的研究却鲜有报道。本项目拟利用依托单位已建立的全细胞催化和酶法合成技术，同时结合有机合成，发展一种具有规模化生产潜力的Neu5Ac衍生物和CMP-Neu5Ac衍生物的高效合成方法，填补该领域中的空白。运用本项目的合成策略，对廉价易得的N-乙酰葡萄糖胺（GlcNAc）进行化学修饰后，再用两步生物催化反应可简便、快速地分别获得各种Neu5Ac衍生物和CMP-Neu5Ac衍生物。本项目将通过该方法大量制备（克级）结构多样的相关化合物，为后续的生物学和药学研究提供充足的物质储备。

组合化学合成，全细胞催化和酶促合成，发展了一种具有规模化生产潜力的Neu5Ac衍生物和CMP-Neu5Ac衍生物的高效合成方法。首先对廉价易得的N-乙酰葡萄糖胺（GlcNAc）进行化学修饰，再通过全细胞催化即可获得Neu5Ac衍生物，最后利用酶催化可进一步得到CMP-Neu5Ac衍生物。通过该方法合成得到了多种Neu5Ac衍生物和CMP-Neu5Ac衍生物，产物可经由凝胶柱和HPLC提纯，结构通过MS和NMR鉴定。在完成计划任务的基础上，进一步开发出了一种“全细胞联合双酶催化”唾液酸寡糖及其衍生物的高效合成体系，得到了若干结构复杂的唾液酸寡糖化合物，该方法的建立，为解决唾液酸生物学领域中“唾液酸寡糖难以获得”的重要基础问题，提供了有利借鉴，同时为后续的生物学和药学研究提供充足的物质储备。