More sustainable biocatalytic imine reductions to chiral amines with hydrogen-driven NADPH recycling operated in batch and continuous flow

该项目属于清洁化学品制造的工业生物技术领域，与制药和精细化学品部门有关。生物催化亚胺还原是合成医药或其他精细化学品用手性胺的合成工具箱中有价值的组成部分。亚胺还原酶依赖于烟酰胺辅助因子(通常是NADPH)将氢化物转移到酶结合的亚胺底物上，而在这些反应中再生NADPH的传统方法通常依赖于超化学计量比的葡萄糖作为还原剂。与金属催化氢化反应相比，使用六碳糖葡萄糖进行单一氢化物转移使整个过程原子效率低下，金属催化氢化反应通过亚胺的C=N双键添加氢气(H2)，得到没有副产品的胺产品。该项目巧妙地利用了介于这些替代方法之间的方法，提供了分离酶生物催化的手性和官能团选择性，以及温和温度和压力下氢气驱动的氢化反应的原子效率。我们通过开发一种创新的NADPH回收策略来实现这一点，该策略使用生物催化的H2激活来推动NADP+的生物催化还原为NADPH，以及在异质载体上处理酶。氢气驱动的辅因子回收具有简化化工产品提纯的额外优势。除了用氢气代替葡萄糖作为原子高效的还原剂外，我们的方法还避免了与辅因子回收步骤相关的pH变化，从而简化了过程化学。该项目是与工业合作伙伴阿斯利康合作的。总体而言，该项目旨在为更可持续的、氢气驱动的NADPH循环提供一个强大的平台，以支持亚胺还原酶用于手性胺的应用。这可以批量实施，也可以连续实施。我们的目标是在一系列与药物和其他精细化学品的合成相关的亚胺还原中证明这一点，这些反应可以在标准的工业用加氢反应器中轻松实施。该方法将适用于后期功能化，以及手性构筑块的合成。结果将在跨越有机合成、生物技术和化学制造主题的会议上公布。该项目属于EPSRC‘制造未来’的研究领域，也与‘能源和脱碳’相关，因为它为化学制造的工业生物技术脱碳。因此，它与EPSRC的战略优先领域‘工程净零点’相关。

This project is in the area of industrial biotechnology for cleaner chemical manufacturing, and is relevant to the pharmaceutical and fine chemicals sectors. Biocatalytic imine reductions are a valuable component in the synthetic tool-box for synthesis of chiral amines for pharmaceuticals or other fine chemicals. Imine reductase enzymes depend on nicotinamide cofactors, usually NADPH, for hydride transfer to an enzyme-bound imine substrate, and conventional approaches for regenerating NADPH during these reactions usually rely upon super-stoichiometric glucose as the reductant. Use of the six-carbon sugar, glucose, for a single hydride-transfer makes the overall process atom-inefficient in contrast to metal-catalysed hydrogenations where hydrogen gas (H2) is added across the C=N double bond of an imine, giving an amine product with no by-products. This project exploits approaches that fall neatly between these alternatives, offering the chiral and functional-group selectivity of isolated-enzyme biocatalysis, alongside the atom-efficiency of H2-driven hydrogenation reactions under mild temperature and pressure. We achieve this by exploiting an innovative strategy for NADPH recycling which uses biocatalysed H2 activation to drive the biocatalytic reduction of NADP+ to NADPH, as well as handling the enzymes on a heterogeneous support. The H2-driven cofactor recycling has the added advantage of simplifying purification of the chemical product. As well as replacing glucose by H2 as atom-efficient reductant, our approach also avoids a pH change associated with the cofactor recycling step, thereby simplifying the process chemistry. The project is conjunction with industrial partner, AstraZeneca. Overall, the project aims to deliver a robust platform for more sustainable, H2-driven NADPH recycling to support application of imine reductases for generation of chiral amines. This may be implemented in batch or continuous flow. We aim to demonstrate this for a series of imine reductions relevant to the synthesis of pharmaceuticals and other fine chemicals, which can be implemented readily within standard industrially-used hydrogenation reactors. The approach would be suitable for late-stage functionalisation, as well as synthesis of chiral building blocks. Results will be presented at conferences spanning organic synthesis, biotechnology and chemical manufacturing topics. This project falls within the EPSRC 'Manufacturing the Future' research area, and is also relevant to 'Energy and Decarbonisation' since it decarbonises industrial biotechnology for chemical manufacturing. As such, it is relevant to the EPSRC strategic priority area of 'Engineering Net Zero'.