Enzymatic Cascades for Stereoselective and Regioselective Amide Bond Assembly.

Amide bond formation is fundamental in nature and is widely used in the synthesis of pharmaceuticals and other valuable products. Current methods for amide synthesis are often step and atom inefficient, requiring the use of protecting groups, deleterious reagents and organic solvents that create significant waste. The development of cleaner and more efficient catalytic methods for amide synthesis remains an urgent unmet need.

Reagent-Based Scaffold Diversity for DNA-Encoded Library Design: Solid Phase Synthesis of DNA-Tagged sp-Rich Heterocycles by SnAP Chemistry.

Reactions that require strictly dry conditions are challenging to translate to a DNA-encoded library format. Controlled pore glass solid support-connected DNA oligonucleotide-aldehyde conjugates could be condensed with SnAP reagents and cyclized to various sp-rich heterocycles. The Boc-group of products provided a handle for product purification, and its facile removal under acidic conditions was tolerated by a chemically stabilized barcode.

Merging enzymes with chemocatalysis for amide bond synthesis.

Amides are one of the most fundamental chemical bonds in nature. In addition to proteins and other metabolites, many valuable synthetic products comprise amide bonds. Despite this, there is a need for more sustainable amide synthesis.

Discovery, characterization and engineering of ligases for amide synthesis.

Coronatine and related bacterial phytotoxins are mimics of the hormone jasmonyl-L-isoleucine (JA-Ile), which mediates physiologically important plant signalling pathways. Coronatine-like phytotoxins disrupt these essential pathways and have potential in the development of safer, more selective herbicides. Although the biosynthesis of coronatine has been investigated previously, the nature of the enzyme that catalyses the crucial coupling of coronafacic acid to amino acids remains unknown.

Nitrosonium ion catalysis: aerobic, metal-free cross-dehydrogenative carbon-heteroatom bond formation.

Catalytic cross-dehydrogenative coupling of heteroarenes with thiophenols and phenothiazines has been developed under mild and environmentally benign reaction conditions. For the first time, NOx+ was applied for catalytic C-S and C-N bond formation. A comprehensive scope for the C-H/S-H and C-H/N-H cross-dehydrogenative coupling was demonstrated with >60 examples.

Selective, Catalytic, and Metal-Free Coupling of Electron-Rich Phenols and Anilides Using Molecular Oxygen as Terminal Oxidant.

Selective oxidative homo- and cross-coupling of electron-rich phenols and anilides was developed using nitrosonium tetrafluoroborate as a catalyst. Oxidative coupling of phenols revealed unusual selectivities, which translated into the unprecedented synthesis of inverse Pummerer-type ketones. Mechanistic studies suggest that oxidative coupling of phenols and anilides shares a common pathway via homolytical heteroatom-hydrogen bond cleavage.

Metal-Free C-O Bond Functionalization: Catalytic Intramolecular and Intermolecular Benzylation of Arenes.

A catalytic, metal-free intramolecular rearrangement of benzyl phenyl ethers using nitrosonium salt as a catalyst is described. The optimized reaction conditions enabled a catalytic and metal-free Friedel-Crafts alkylation reaction with benzylic alcohols, producing water as the stoichiometric byproduct. A comprehensive scope (>50 examples) for both approaches and application in drug synthesis were demonstrated.

Aerobic, Metal-Free, and Catalytic Dehydrogenative Coupling of Heterocycles: En Route to Hedgehog Signaling Pathway Inhibitors.

The nitrosonium ion-catalyzed dehydrogenative coupling of heteroarenes under mild reaction conditions is reported. The developed method utilizes ambient molecular oxygen as a terminal oxidant, and only water is produced as byproduct. Dehydrogenative coupling of heteroarenes translated into the rapid discovery of novel hedgehog signaling pathway inhibitors, emphasizing the importance of the developed methodology.

Sustainable, Oxidative, and Metal-Free Annulation.

Annulation has received steadily growing interest in the interplay with the increasing emphasis towards selective C-H bond functionalization reactions. Metal-free oxidative annulation through functionalization of inert and abundant C-H bonds offers great improvements in terms of atom- and step-economics as well as reduced waste production under mild reaction conditions. Annulation is considered to be a highly efficient strategy for the construction of cyclic molecules because at least two new bonds are formed within a single reaction step.

Selective transition-metal-free vicinal -dihydroxylation of saturated hydrocarbons.

A transition-metal-free -dihydroxylation of saturated hydrocarbons under ambient reaction conditions has been developed. The described approach allows a direct and selective synthesis of vicinal diols. The new reaction thereby proceeds radical iodination and a sequence of oxidation steps.

Regioselective Metal-Free Cross-Coupling of Quinoline N-Oxides with Boronic Acids.

A novel and operationally simple one-step C-H bond functionalization of quinoline N-oxides to 2-substituted quinolines was developed. This approach enables the regioselective functionalization under external oxidant- and metal-free conditions. The developed transformation represents the first application of the Petasis reaction in functionalization of heterocycles.