Next Generation Enzymatic and Integrated Catalytic Approaches for Amide Synthesis

为了一个可持续的未来，迫切需要获得制药和其他先进材料的新途径。在这个项目中，我们的目标是开发新的、更有效和可持续的方法来构建酰胺键，这种键在许多领先的制药、农用化学品、聚合物和其他有价值的材料中很常见。通常，酰胺是由羧酸和胺使用成熟的偶联剂合成的。虽然这种传统的方法被广泛使用，但它极其浪费，缺乏选择性，而且使用有毒试剂。羧酸和胺的偶联通常需要一种或多种相当于一种或多种偶联试剂，这造成了相当大的浪费以及反应纯化方面的问题。保护基团通常是封闭前体中其他反应性官能团所必需的，因此通常需要多个步骤(保护-偶联-去保护)才能生成单一的酰胺键，从而消耗更多昂贵和有害的试剂。外消旋/差向异构化也是手性前体偶联时的常见问题。这种立体化学的丧失在药物的合成中是有问题的，药物需要作为单一的立体异构体来生产。最后，传统的酰胺偶联反应通常使用偶极非质子溶剂或氯化溶剂，这带来了进一步的安全问题，并增加了与处理它们相关的成本。在这个项目中，我们的目标是使用一种基于生物技术的方法来以更高效和环境可持续的方式提供酰胺。为了实现这一目标，我们将探索两种互补的方法来生产酰胺。首先，我们的目标是设计自然催化剂(酶)，以创造新的酶变体(突变体)，可以连接多种酸和胺底物。此外，我们计划将酶与过渡金属催化剂结合起来，创造出合成酰胺的新的集成催化方法。通过结合酶催化和化学催化的优点，我们的目标是打开新的转化和路线，以获得有价值的酰胺，这将是现有方法无法获得的。自然界已经创造了许多将酸和胺偶联以形成酰胺键的方法，其中最常见的方法依赖于一种名为ATP的分子来激活促进胺底物攻击的羧酸基。这种酶被称为酰胺连接酶，它们同时具有与羧酸和胺底物的结合部位。通常情况下，酰胺连接酶性质提供的底物范围较窄。我们建议通过改造连接酶的两个结合部位来创造新的突变酶，这种酶可以连接更广泛的底物。这种新的酶将在水中发挥作用，不需要额外的昂贵或有毒试剂，因此可以用于更环保、更具成本效益的合成有价值的酰胺，这是生产药物和其他重要分子所需的。除了酰胺连接酶，我们还将探索一类不同的酶--氰基水合酶(NHase)在酰胺合成中的应用。氨酶将水加到氰化物(带有-CN基团的分子)中，生成伯胺(-CONH2)。为了扩大NHase的范围，我们的目标是将这些酶与一种过渡金属催化剂结合起来，这种催化剂可以在伯酰胺上安装一个官能团，以生成更多样化的仲酰胺(-CONHR)，这通常存在于制药等领域。通常情况下，将酶与金属催化剂结合是有问题的，因为两种催化剂是不相容的。例如，金属可以与酶结合并使催化剂失活。为了克服这个问题，我们设计了一系列方法来区分酶和金属催化剂，这样两者就可以在一个(一锅)反应中结合起来。这也可以提供从替代原料(前体)到酰胺的更直接的路线。

New routes to pharmaceuticals and other advanced materials are urgently required for a sustainable future. In this project we aim to develop novel, more efficient and sustainable methods for constructing amide bonds, which are common in many leading pharmaceuticals, agrochemicals, polymers and other valuable materials. Typically, amides are constructed synthetically from carboxylic acids and amines using well established coupling reagents. Although this traditional approach is widely used, it is extremely wasteful, lacks selectivity and uses toxic reagents. Coupling of carboxylic acids and amines typically requires one equivalent or more of coupling reagents, creating considerable waste as well as problems in reaction purification. Protecting groups are often necessary to block other reactive functionality in the precursors, so multiple steps (protect-couple-deprotect) are usually required to generate a single amide bond, consuming further expensive and deleterious reagents. Racemization/epimerization is also a common problem when coupling chiral precursors. This loss of stereochemistry is problematic in the synthesis of drugs which need to be produced as single stereoisomers. Finally, traditional amide coupling reactions typically employ dipolar aprotic solvents or chlorinated solvents, which present further safety issues and increased costs associated with their disposal.In this project we aim to use a biotechnology-based approach to deliver amides in a more efficient and environmentally sustainable manner. To achieve this, we will explore two complementary methods for producing amides. First, we aim to engineer natures catalysts (enzymes) to create new enzyme variants (mutants) that can couple a wide range of acid and amine substrates. In addition, we plan to combine enzymes with transition metal catalyst to create new integrated catalytic approaches to amides. By combining the best of enzymatic and chemocatalysis, we aim to open new transformations and routes to valuable amides that would be inaccessible using existing methods. Nature has created a number of ways to couple acids and amines to make amide bonds with the most common methods relying on a molecule called ATP to activate the carboxylic acid group facilitating attack of the amine substrate. Such enzymes are called amide ligases and they possess binding sites for both the carboxylic acid and amine substrates. Normally the amide ligases nature provides have narrow substrate scope. We propose engineering both binding sites of the ligase enzymes to create new mutant enzymes that can couple a much wider range of substrates. The new enzymes will work in water, require no additional expensive or toxic reagents and can therefore be utilised for the more environmentally and cost-effective synthesis of valuable amides required for production of pharmaceuticals and other important molecules. In addition to amide ligases enzymes, we will also explore the utility of a different class of enzyme, the nitrile hydratases (NHase), for amide synthesis. NHase add water to nitriles (molecules with -CN groups) producing to primary amides (-CONH2). To broaden the scope of NHase we aim to combine these enzymes with a transition metal catalyst that can install a functional group on the primary amide to create more diverse secondary amides (-CONHR) which are typically found in pharmaceuticals etc. Normally combining enzymes with metal catalysts is problematic as the two catalysts are incompatible. For example, metals can bind to enzymes and deactivate the catalysts. To overcome this problem, we have devised a range of methods for compartmentalising enzymes and metal catalysts, in such a way that the two can be combine in a single (one-pot) reaction. This can also provide more direct routes to amides from alternative feedstocks (precursors).