Macrocyclic natural products are conformationally restricted molecules that often have improved ability to bind with high affinity and selectivity on a target. Within macrocycle chemistry, macrolactone formation is a particularly challenging transformation and has spurred the development of highly diverse synthetic strategies. A key strategy that is missing is a chemoenzymatic approach to this challenge, and the logical place to look for such a catalyst is the thioesterases (TEs) from the biosynthetic pathways that generate these molecules in Nature. These TEs are α/β-hydrolases containing an active site serine or cysteine and a conserved histidine/aspartate catalytic diad. The research presented here describes the development of two related TE domains from resorcylic acid lactone polyketide synthases found in various fungi. Unlike their bacterial counterparts these macrocyclization catalysts have proven to be stereotolerant with regard to the secondary alcohols involved in macrocyclization. Further work has demonstrated that they are also amenable to generating 12- to 18-member macrolactones. These TE domains can also catalyze macrolactam and cyclic depsipeptide formation, setting the stage for these enzymes to serve as a platform for catalyst development. The development of 2,3-diaminopropionate (DAP) incorporation in place of the active site Ser to trap acyl-enzyme intermediates was used to structurally characterize the formation of a macrocyclic trimer. This technique will be broadly applicable to characterizing other TEs. Overall the research presented here lays the foundation for the long term development of TEs as macrocyclization biocatalysts.

Macrocyclic peptides have been identified as key backbones in several biologically active compounds. They have been considered as great inspiration in the development of novel cyclic scaffolds in medicinal chemistry, notably in the introduction of α-helically constricted stapled peptides with the ability to mimic biologically relevant α-helices. DNA-binding transcription factors often bind their DNA promoter through an α-helix, making a parallel with stapled peptides as inhibitors. Despite this relevant feature, DNA-binding stapled peptides are highly unrepresented in the literature, as will be discussed here in a review. We also further expand this area of research with a study of DNA binding stapled peptide ana-logues with the goal of optimizing and investigating the DNA binding and antivirulence of an RpoN-based stapled peptide. Cyclic depsipeptides are highly biologically active natural product molecules however their synthesis can be challenging with the presence of a macrolactone. Due to this complexity, solid phase peptide synthesis strategies have been utilized to access peptide intermediates that can be synthetically macrocyclized using solution phase or on-resin approaches via macrolactam or macrolactone formation. A representative number of total syntheses in the literature is reviewed. Furthermore, we describe here the chemical total synthesis and chemoenzymatic synthesis of seongsanamide E cyclic depesipeptide via thioesterase medi-ated macrolactonization. Cyclic depsipeptides also play major roles in their producing organisms, notably siderophores capable of chelating and transporting iron. The biosynthesis of fungal siderophores is poorly explored, such as the iterative mechanism of oligomeric compound fusarinine C. We explore the synthesis of the previously never synthesized fusarinine C monomer to be utilized as a di-domain inhibitor of the adenylating-thiolation domains of the non-ribosomal peptide synthetase (NRPS) SidD.

Fungal polyketides are a diverse class of natural products that possess many pharmacological properties, including anticancer properties. These properties are evident in the resorcylic acid lactones, a family of polyketides, including zearalenone and radicicol, which shows potent inhibition of tumour cell growth. The key step in the biosynthesis of these lactones is macrocyclization of a linear carboxylic acid into the macrolactone. This reaction is catalyzed by a polyketide synthase (PKS) thioesterase enzyme. Bacterial PKS thioesterases (TEs) have been extensively studied and their substrate specificity has been characterized in vitro. They are highly substrate selective for the macrocyclization reaction. Since Fungal PKS TEs show little sequence homology to bacterial TEs, we have begun investigating their substrate specificity. In particular we are examining the ability of fungal TEs to macrocyclize compounds with varying ring sizes, stereogenic configuration, and nucleophiles. Herein we present the synthesis of a number of diverse TE substrates and the in vitro macrocyclization results for the TEs from zearalenone and radicicol biosynthetic pathway with these substrates.

Fungal polyketides are a diverse class of natural products that possess many pharmacological properties, including anticancer properties. These properties are evident in the resorcylic acid lactones, a family of polyketides, including zearalenone and radicicol, which shows potent inhibition of tumour cell growth. The key step in the biosynthesis of these lactones is macrocyclization of a linear carboxylic acid into the macrolactone. This reaction is catalyzed by a polyketide synthase (PKS) thioesterase enzyme. Bacterial PKS thioesterases (TEs) have been extensively studied and their substrate specificity has been characterized in vitro. They are highly substrate selective for the macrocyclization reaction. Since Fungal PKS TEs show little sequence homology to bacterial TEs, we have begun investigating their substrate specificity. In particular we are examining the ability of fungal TEs to macrocyclize compounds with varying ring sizes, stereogenic configuration, and nucleophiles. Herein we present the synthesis of a number of diverse TE substrates and the in vitro macrocyclization results for the TEs from zearalenone and radicicol biosynthetic pathway with these substrates.

Fungal polyketides are a diverse class of natural products that possess many pharmacological properties, including anticancer properties. These properties are evident in the resorcylic acid lactones, a family of polyketides, including zearalenone and radicicol, which shows potent inhibition of tumour cell growth. The key step in the biosynthesis of these lactones is macrocyclization of a linear carboxylic acid into the macrolactone. This reaction is catalyzed by a polyketide synthase (PKS) thioesterase enzyme. Bacterial PKS thioesterases (TEs) have been extensively studied and their substrate specificity has been characterized in vitro. They are highly substrate selective for the macrocyclization reaction. Since Fungal PKS TEs show little sequence homology to bacterial TEs, we have begun investigating their substrate specificity. In particular we are examining the ability of fungal TEs to macrocyclize compounds with varying ring sizes, stereogenic configuration, and nucleophiles. Herein we present the synthesis of a number of diverse TE substrates and the in vitro macrocyclization results for the TEs from zearalenone and radicicol biosynthetic pathway with these substrates.

Fungal polyketides are a diverse class of natural products that possess many pharmacological properties, including anticancer properties. These properties are evident in the resorcylic acid lactones, a family of polyketides, including zearalenone and radicicol, which shows potent inhibition of tumour cell growth. The key step in the biosynthesis of these lactones is macrocyclization of a linear carboxylic acid into the macrolactone. This reaction is catalyzed by a polyketide synthase (PKS) thioesterase enzyme. Bacterial PKS thioesterases (TEs) have been extensively studied and their substrate specificity has been characterized in vitro. They are highly substrate selective for the macrocyclization reaction. Since Fungal PKS TEs show little sequence homology to bacterial TEs, we have begun investigating their substrate specificity. In particular we are examining the ability of fungal TEs to macrocyclize compounds with varying ring sizes, stereogenic configuration, and nucleophiles. Herein we present the synthesis of a number of diverse TE substrates and the in vitro macrocyclization results for the TEs from zearalenone and radicicol biosynthetic pathway with these substrates.

Directing groups (DGs) are moieties installed onto organic molecules to confer regioselectivity in subsequent reactions. DGs have found utility in selective CH activations catalyzed by transition metal (TM) catalysis on starting materials with multiple CH bonds. Despite their utility, DGs are scarcely used in industrial applications due to the generally wasteful nature of conventional DG strategies and their associated increase in step-count. Transient directing groups (TDGs) have been developed to overcome these limitations, with additives reversibly forming adducts with compounds of interest prior to the DG-mediated CH activation, in one-pot processes. However, the use of TDGs still requires harsh conditions to achieve significant yields, hindering broad applications. Chemoenzymatic catalytic cascades have attracted attention due to the mild and environmentally friendly nature of biocatalysis, with the greatest challenge being compatibility issues between biocatalytic and traditional chemical transformations. Here we propose a concurrent chemoenzymatic catalytic cascade that would enable TM-catalyzed DG chemistry via flanking biocatalytic reductive amination to install, and oxidative deamination to remove, a TDG. Preliminary efforts have identified some incompatibilities arising from the biocatalytic portion of the cascade, namely substrate specificity and organic co-solvent tolerance, that need to be addressed to achieve the proposed chemoenzymatic cascade in a one-pot concurrent protocol.

No / Mechanochemical chemoenzymatic peptide and amide bond formation catalysed by papain was studied by ball milling. Despite the high-energy mixing experienced inside the ball mill, the biocatalyst proved stable and highly efficient to catalyse the formation of α,α- and α,β-dipeptides. This strategy was further extended to the enzymatic acylation of amines by milling, and to the mechanosynthesis of a derivative of the valuable dipeptide L-alanyl-L-glutamine. / We thank RWTH Aachen University for support from the Distinguished Professorship Program funded by the Excellence Initiative of the German federal and state governments. EPSRC, grant no. EP/L019655/1.

Glycans are macromolecules that contain several classes. Glycans can play an important role in biological activities. Studying the cell surface glycans can provide a very powerful way to understand the fundamental process. Also it could help to regulate expected cell response. Thus it is very necessary to have a method to detect cell- surface glycans efficiently. An efficient method for glycan detection is necessary. Metabolic glycan labeling and chemoenzymatic glycan labeling are most commonly used. Chemoenzymatic glycan labeling is a rapid and sensitive method which also has high specificity. This method can be applied in both vitro and vivo. However the availability of unnatural sugar nucleotides functioned by bioorthogonal groups is the main limitation for chemoenzymatic labeling. In this thesis, UDP-GlcNAc and UDP-GalNAc derivatives were prepared for further chemoenzymatic labeling by using chemoenzymatic synthesis method.

Amine transaminases are enzymes that catalyze the mild and selective formation of primary amines, which are useful building blocks for biologically active compounds and natural products. In order to make the production of these kinds of compounds more efficient from both a practical and an environmental point of view, amine transaminases were incorporated into multi-step one-pot reactions. With this kind of methodology there is no need for isolation of intermediates, and thus unnecessary work-up steps can be omitted and formation of waste is prevented. Amine transaminases were successfully combined with other enzymes for multi-step synthesis of valuable products: With ketoreductases all four diastereomers of a 1,3-amino alcohol could be obtained, and the use of a lipase allowed for the synthesis of natural products in the form of capsaicinoids. Amine transaminases were also successfully combined with metal catalysts based on palladium or copper. This methodology allowed for the amination of alcohols and the synthesis of chiral amines such as the pharmaceutical compound Rivastigmine. These examples show that the use of amine transaminases in multi-step one-pot reactions is possible, and hopefully this concept can be further developed and applied to make industrial processes more sustainable and efficient in the future. / <p>QC 20170113</p>