Gary A. Molander

Bioconjugation has emerged as a powerful tool in modern chemical biology for creating new molecules with applications in both research and therapeutics. The modification of biomacromolecules—such as proteins, peptides, nucleic acids, carbohydrates, and related biomolecules—contributes to various fields, including biochemistry and materials science, with relevance to the development of biopharmaceuticals, such as antibody–drug conjugates. Over the past two decades, there has been a growing interest in developing simpler, milder, site‐selective, and high‐yielding synthetic protocols. Among these, photoinduced methods stand out, as light is a sustainable energy source that enables the formation of highly reactive intermediates under mild reaction conditions, typically well tolerated in bioconjugation. In recent years, photocatalyzed light‐induced chemical processes have been extensively explored. However, reactions that proceed without external photocatalysts are especially appealing, particularly from economic and sustainability viewpoints. This Perspective article discusses the strategies developed over the past decade for photocatalyst‐free photoinduced bioconjugation, with special focus on the formation of electron‐donor/electron‐acceptor complexes. Both biomolecule synthesis and late‐stage functionalization will be addressed. Experimental limitations and the applicability of these protocols in biocompatible contexts will be evaluated. Beyond macromolecules, monomeric units, such as amino acids and nucleotides, are also considered.

Antibody–drug conjugates (ADCs) represent a promising class of targeted therapeutics, combining the specificity of antibodies with the potency of cytotoxic drugs to enhance therapeutic efficacy while minimizing off-target effects. The development of new chemical methods for bioconjugation is essential to generate ADCs and to optimize their stability, efficacy, and safety. Traditional conjugation methods often face challenges related to site-selectivity and heterogeneous product mixtures, highlighting the need to develop new, innovative chemical strategies. Photoredox chemistry emerges as a powerful tool in this context, enabling precise, mild, and selective modifications of peptides and proteins. By harnessing light to drive chemical transformations, photoredox techniques can facilitate the synthesis of antibody bioconjugates. This perspective will discuss the drive to develop and empower photoredox methods applied to antibody functionalization.

Small, strained carbocyclic systems have fascinated organic chemists from both a theoretical and synthetic standpoint. These systems often challenge conventional wisdom when it comes to molecular structure and tactics for chemical construction. The cyclopropyl motif is one such ring system that remains at the forefront of method development in the modern era. With the advent of an array of non‐traditional building blocks, a range of new cyclopropanation processes using one‐ and two‐electron strategies have been developed that not only overcome the synthetic shortcomings of classical approaches but also provide entry into a wide range of new classes of cyclopropanes. This review discusses recent advances in this area with an emphasis on their mechanistic underpinnings and potential applications. Additionally, a concise overview of the properties of and traditional approaches to cyclopropanes is provided.

The direct utilization of simple and abundant feedstocks in carbon‐carbon bond‐forming reactions to embellish sp³‐enriched chemical space is highly desirable. Herein, we report a novel photochemical deoxygenative hydroalkylation of unactivated alkenes with readily available carboxylic acid derivatives. The reaction displays broad functional group tolerance, accommodating carboxylic acid‐, alcohol‐, ester‐, ketone‐, amide‐, silane‐, and boronic ester groups, as well as nitrile‐containing substrates. The reaction is operationally simple, mild, and water‐tolerant, and can be carried out on multigram‐scale, which highlights the utility of the method to prepare value‐added compounds in a practical and scalable manner. The synthetic application of the developed method is further exemplified through the synthesis of suberanilic acid, a precursor of vorinostat, a drug used for the treatment of cutaneous T‐cell lymphoma. A novel mechanistic approach was identified using thiol as a nucleophilic catalyst, which forms a key intermediate for this transformation. Furthermore, electrochemical studies, quantum yield, and mechanistic experiments were conducted to support a proposed catalytic cycle for the transformation.

The direct utilization of simple and abundant feedstocks in carbon‐carbon bond‐forming reactions to embellish sp³‐enriched chemical space is highly desirable. Herein, we report a novel photochemical deoxygenative hydroalkylation of unactivated alkenes with readily available carboxylic acid derivatives. The reaction displays broad functional group tolerance, accommodating carboxylic acid‐, alcohol‐, ester‐, ketone‐, amide‐, silane‐, and boronic ester groups, as well as nitrile‐containing substrates. The reaction is operationally simple, mild, and water‐tolerant, and can be carried out on multigram‐scale, which highlights the utility of the method to prepare value‐added compounds in a practical and scalable manner. The synthetic application of the developed method is further exemplified through the synthesis of suberanilic acid, a precursor of vorinostat, a drug used for the treatment of cutaneous T‐cell lymphoma. A novel mechanistic approach was identified using thiol as a nucleophilic catalyst, which forms a key intermediate for this transformation. Furthermore, electrochemical studies, quantum yield, and mechanistic experiments were conducted to support a proposed catalytic cycle for the transformation.

The use of visible light as the driving force to trigger chemical transformations represents an attractive tool for organic synthesis, and it has been demonstrated to be an important and well-established strategy for accessing novel bond connections in a unique way via radical intermediates. This powerful synthetic tool is under continuous development and is finding ever-increasing applications in DNA-encoded library (DEL) synthesis. Since 2018, DEL chemists have new chemical space available thanks to the implementation of visible-light-mediated methods. This chapter details the state-of-the-art of on-DNA photoredox-catalyzed transformations Specifically, this review covers simple photoredox reactions, dual-catalytic metallaphotoredox reactions, and photoredox reactions initiated by electron donor/electron-acceptor (EDA) complexes.

The advancement of sustainable photoredox catalysis in synthetic organic chemistry has evolved immensely because of the development of versatile and cost‐effective reagents. In recent years, a substantial effort has been dedicated to exploring the utility of formic acid salts in various photochemical reactions. In this context, formates have demonstrated diverse capabilities, functioning as reductants, sources of carbonyl groups, and reagents for hydrogen atom transfer. Notably, the CO₂⋅^– radical anion derived from formate exhibits strong reductant properties for cleaving both C−X and C−O bonds. Moreover, these salts play a pivotal role in carboxylation reactions, further highlighting their significance in a variety of photochemical transformations. The ability of formates to serve as reductants, carbonyl sources, and hydrogen atom transfer reagents reveal exciting possibilities in synthetic organic chemistry. This minireview highlights an array of captivating discoveries, underscoring the crucial role of formates in diverse and distinctive photochemical methods, enabling access to a wide range of value‐added compounds.

The advancement of sustainable photoredox catalysis in synthetic organic chemistry has evolved immensely because of the development of versatile and cost‐effective reagents. In recent years, a substantial effort has been dedicated to exploring the utility of formic acid salts in various photochemical reactions. In this context, formates have demonstrated diverse capabilities, functioning as reductants, sources of carbonyl groups, and reagents for hydrogen atom transfer. Notably, the CO₂⋅^– radical anion derived from formate exhibits strong reductant properties for cleaving both C−X and C−O bonds. Moreover, these salts play a pivotal role in carboxylation reactions, further highlighting their significance in a variety of photochemical transformations. The ability of formates to serve as reductants, carbonyl sources, and hydrogen atom transfer reagents reveal exciting possibilities in synthetic organic chemistry. This minireview highlights an array of captivating discoveries, underscoring the crucial role of formates in diverse and distinctive photochemical methods, enabling access to a wide range of value‐added compounds.

The emergence of DNA-encoded library (DEL) technology has provided a considerable advantage to the pharmaceutical industry in the pursuit of discovering novel therapeutic candidates for their drug development initiatives. This combinatorial technique not only offers a more economical, spatially efficient, and time-saving alternative to the existing ligand discovery methods, but also enables the exploration of additional chemical space by utilizing novel DNA-compatible synthetic transformations to leverage multifunctional building blocks from readily available substructures. In this report, a decarboxylative-based hydroalkylation of DNA-conjugated N-vinyl heterocycles enabled by single-electron transfer (SET) and subsequent hydrogen atom transfer through electron-donor/electron-acceptor (EDA) complex activation is detailed. The simplicity and robustness of this method permits inclusion of a broad array of alkyl radical precursors and DNA-tethered nitrogenous heterocyles to generate medicinally relevant substituted heterocycles with pendant functional groups. Moreover, a successful telescoped route provides the opportunity to access a broad range of intricate structural scaffolds by employing basic carboxylic acid feedstocks.