Aqueous Flavin Photoredox Catalysis Drives Exclusive C3-Alkylation of Indolyl Radical Cations in Route to Unnatural Tryptophan Mimetics.

One way to build chemical diversity into indoles is to oxidize them to indolyl radical cations (Ind). These intermediates can accept new functional groups across C2-C3 bonds or independently at C2. Less encountered is selective diversification at C3, a position plagued by competing dearomative side reactions.

Flavin Metallaphotoredox Catalysis: Synergistic Synthesis in Water.

Combining a transition metal with a photocatalyst can drive modern synthetic chemistry. For transformations performed in water, this concept has been largely unexplored. We report the successful merger of a biocompatible flavin photocatalyst with a palladium catalyst to build isotopically enriched peptidomimetics, to mediate conjugate addition and functionalization reactions, and to assemble unprotected proteinogenic and nonproteinogenic peptides, in water.

carba-Nucleopeptides (cNPs): A Biopharmaceutical Modality Formed through Aqueous Rhodamine B Photoredox Catalysis.

Exchanging the ribose backbone of an oligonucleotide for a peptide can enhance its physiologic stability and nucleic acid binding affinity. Ordinarily, the eneamino nitrogen atom of a nucleobase is fused to the side chain of a polypeptide through a new C-N bond. The discovery of C-C linked nucleobases in the human transcriptome reveals new opportunities for engineering nucleopeptides that replace the traditional C-N bond with a non-classical C-C bond, liberating a captive nitrogen atom and promoting new hydrogen bonding and π-stacking interactions.

Combining flavin photocatalysis with parallel synthesis: a general platform to optimize peptides with non-proteinogenic amino acids.

Most peptide drugs contain non-proteinogenic amino acids (NPAAs), born out through extensive structure-activity relationship (SAR) studies using solid-phase peptide synthesis (SPPS). Synthetically laborious and expensive to manufacture, NPAAs also can have poor coupling efficiencies allowing only a small fraction to be sampled by conventional SPPS. To gain general access to NPAA-containing peptides, we developed a first-generation platform that merges contemporary flavin photocatalysis with parallel synthesis to simultaneously make, purify, quantify, and even test up to 96 single-NPAA peptide variants the unique combination of boronic acids and a dehydroalanine residue in a peptide.

Solid-phase XRN1 reactions for RNA cleavage: application in single-molecule sequencing.

Modifications in RNA are numerous (∼170) and in higher numbers compared to DNA (∼5) making the ability to sequence an RNA molecule to identify these modifications highly tenuous using next generation sequencing (NGS). The ability to immobilize an exoribonuclease enzyme, such as XRN1, to a solid support while maintaining its activity and capability to cleave both the canonical and modified ribonucleotides from an intact RNA molecule can be a viable approach for single-molecule RNA sequencing. In this study, we report an enzymatic reactor consisting of covalently attached XRN1 to a solid support as the groundwork for a novel RNA exosequencing technique.