Dissertation, RWTH Aachen University, 2019; Aachen 1 Online-Ressource (123 Seiten) : Illustrationen, Diagramme (2020). = Dissertation, RWTH Aachen University, 2019, Chemoenzymatic cascade reactions are an emerging field in organic synthesis, as they combine the selectivity of enzymes with the reactivity of chemical catalysts. Due to their broad reaction scope, metal catalysts are often used in chemoenzymatic cascade reactions. However, combinations of metal- and biocatalysts often suffer from mutual inactivation. While metal catalysts can coordinate to amino acids of the enzyme, cellular components can inactivate the metal catalyst.In this thesis, two strategies for the combination of transition metal catalysts and enzymes were designed. The first cascade reaction focused on the combination of a Cu scorpionate catalyst active in Sonogashira cross-coupling, and a variant of the monooxygenase P450 BM3 (A74G F87V L188Q, P450 BM3 trio). So far, chemoenzymatic cascade reactions involving cross-coupling reactions were limited to the use of palladium catalysts for Suzuki cross-coupling. The Cu scorpionate catalyst was active in DMSO and fully converted 2-iodophenol and 3-dimethylamino-1-propyne to N,N-dimethyl-2-benzofuranmethanamine. P450 BM3 trio was probed towards conversion of the benzofuran derivative. Reactions with purified N,N-dimethyl-2-benzofuranmethanamine and P450 BM3 trio yielded up to 88% of a novel methylene bridged bis(2-substituted) benzofuran, N,N’-bis(benzofuran-2-ylmethyl)-N,N’-dimethylmethandiamine. The product was solely accessible via enzymatic functionalization by P450 BM3 trio, as side chain hydroxylation of N,N-dimethyl-2-benzofuranmethanamine and further formaldehyde elimination was required for the formation of N,N’-bis(benzofuran-2-ylmethyl)-N,N’-dimethyl-methandiamine. The selectivity towards benzofurans in Sonogashira cross-coupling was lost when alkynes substituted with secondary or primary amines were involved. In the next step, the cascade reaction was investigated in a sequential fashion after completion of the Sonogashira cross-coupling, as reaction conditions for the Cu scorpionate catalyst were not tolerated by the enzyme. P450 BM3 trio was inhibited in one-pot reactions with the Cu scorpionate catalyst, most likely because of the metal catalyst or its decomposition products. Thus, an alternative approach was pursued to overcome inhibition of the biocatalyst. Prior to biocatalysis, residual Cu catalyst was scavenged by addition of the chelating agent EDTA. Using this simple approach, the one-pot two-step cascade yielded up to 84% N,N’-bis(benzofuran-2-ylmethyl)-N,N’-dimethylmethandiamine. The depicted cascade reaction is the first example of Cu-catalyzed Sonogashira cross-coupling combined with an enzyme. The second part of this thesis focused on the combination of a biohybrid catalyst and an enzyme. The necessity to compartmentalize or immobilize catalysts in cascade reactions stems from their mutual incompatibility, which is often encountered. Biohybrid catalysts result from the incorporation of transition metal catalysts into protein scaffolds. The protein scaffold enables reactivity in aqueous solution, rendering the biohybrid catalysts compatible with enzymes. So far, however, chemoenzymatic cascade reactions involving biohybrid catalysts are limited to cofactor regeneration by either the metal- or biocatalysts. The first example involving two biohybrid catalysts in a synthetic cascade reaction was described by Sauer et al. Within this thesis, the decarboxylase FDC1 from S. cerevisiae and the biohybrid catalyst FhuA GH were successfully combined in a one-pot two-step cascade reaction to produce symmetrical stilbene derivatives. Reactions involving FDC1 and FhuA-GH yielded up to 74% stilbene derivatives, while in control experiments with the water-soluble Grubbs-Hoveyda catalyst AquaMet, only traces of stilbenes were obtained. Through immobilization of the transition metal catalyst in a protein scaffold, the former is shielded from inhibiting components present in the cell-free extract. The compartmentalization of the metal catalyst by immobilization in a protein scaffold further facilitated post-reaction metal removal by extraction. As the biohybrid catalyst remains in the aqueous phase due to the solubility of the protein scaffold, it is simply separated from the product. The metal contamination in extracted product fractions of cascade reactions with the biohybrid catalyst was significantly lower compared to reactions with the soluble catalyst (1 ppm vs. 24 ppm), most likely due to the small molecule catalyst AquaMet being more easily extracted into the product fraction. The measured ruthenium content in cascade reactions involving the biohybrid catalyst was below a content of 10 ppm required for production in pharmaceutical industry. The presented cascade reaction combining FDC1 and FhuA-GH is the first example of a synthetic chemoenzymatic cascade reaction involving a biohybrid catalyst and demonstrates a facile approach to separate metal impurities from the product fraction. Further, a first approach towards whole cell cascade reactions involving biohybrid catalysts was pursued by combining FhuA-GH with cells harboring FDC1. However, the intermediate styrene was not released from the cell. Therefore, the overall yield of the cascade reaction was comparably low (7%). Nevertheless, the whole cell cascade reaction can be considered as a first step towards a concurrent reaction mode, as the biocatalyst is shielded from SDS through the cell membrane and shows quantitative conversion of the substrate. Systems for the release of styrene are to be investigated for future applications., Published by Aachen