Macrocyclization strategies for the total synthesis of cyclic depsipeptides

Macrocyclic-based strategy in drug design: From lab to the clinic

Macrocyclic compounds have emerged as potent tools in the field of drug design, offering unique advantages for enhancing molecular recognition, improving pharmacokinetic properties, and expanding the chemical space accessible to medicinal chemists. This review delves into the evolutionary trajectory of macrocyclic-based strategies, tracing their journey from laboratory innovations to clinical applications. Beginning with an exploration of the defining structural features of macrocycles and their impact on drug-like characteristics, this discussion progresses to highlight key design principles that have facilitated the development of diverse macrocyclic drug candidates. Through a series of illustrative representative case studies from approved macrocyclic drugs and candidates spanning various therapeutic areas, particular emphasis is placed on their efficacy in targeting challenging protein-protein interactions, enzymes, and receptors. Additionally, this review thoroughly examines how macrocycles effectively address critical issues such as metabolic stability, oral bioavailability and selectivity. Valuable insights into optimization strategies employed during both approved and clinical phases underscore successful translation of promising leads into efficacious therapies while providing valuable perspectives on harnessing the full potential of macrocycles in drug discovery and development endeavors.

Synthesis of macrocyclic thiolactone peptides via photochemical intramolecular radical acyl thiol-ene ligation

A photochemical acyl thiol-ene reaction can be used to rapidly cyclise fully unprotected peptides bearing both a thioacid and alkene to form peptide thiolactones. This strategy represents the first reported synthesis of peptide thiolactones under radical-mediated conditions.

Backbone-Determined Antiarrhythmic Structure-Activity Relationships for a Mirror Image, Oligomeric Depsipeptide Natural Product

Cyclic oligomeric depsipeptides (COD) are a structural class within naturally occurring compounds with a wide range of biological activity. Verticilide is a COD (24-membered ring) that was identified by its inhibition of insect ryanodine receptor (RyR). We have since found that the enantiomer of verticilide (ent-verticilide, 1) is a potent inhibitor of mammalian RyR2, a cardiac calcium channel, and therefore a potential antiarrhythmic agent. Oddly, nat-verticilide does not inhibit RyR2. To further develop ent-verticilide as an antiarrhythmic, we explored potential SAR through systematic modification of the ester's functionality to both N-H and N-Me amides. The syntheses of these ent-verticilide-inspired analogs are detailed using a monomer-based platform enabled by enantioselective catalysis. Two analogs among 23 exhibited measurable reduction of calcium sparks in a functional assay of RyR2 activity. These findings illustrate the value of natural product-inspired therapeutic development, but the less-studied approach where the non-natural enantiomeric series harbors important SAR.

Unearthing naturally-occurring cyclic antibacterial peptides and their structural optimization strategies

Natural products with antibacterial activity are highly desired globally to combat against multidrug-resistant (MDR) bacteria. Antibacterial peptide (ABP), especially cyclic ABP (CABP), is one of the abundant classes. Most of them were isolated from microbes, demonstrating excellent bactericidal effects. With the improved proteolytic stability, CABPs are normally considered to have better druggability than linear peptides. However, most clinically-used CABP-based antibiotics, such as colistin, also face the challenges of drug resistance soon after they reached the market, urgently requiring the development of next-generation succedaneums. We present here a detail review on the novel naturally-occurring CABPs discovered in the past decade and some of them are under clinical trials, exhibiting anticipated application potential. According to their chemical structures, they were broadly classified into five groups, including (i) lactam/lactone-based CABPs, (ii) cyclic lipopeptides, (iii) glycopeptides, (iv) cyclic sulfur-rich peptides and (v) multiple-modified CABPs. Their chemical structures, antibacterial spectrums and proposed mechanisms are discussed. Moreover, engineered analogs of these novel CABPs are also summarized to preliminarily analyze their structure-activity relationship. This review aims to provide a global perspective on research and development of novel CABPs to highlight the effectiveness of derivatives design in identifying promising antibacterial agents. Further research efforts in this area are believed to play important roles in fighting against the multidrug-resistance crisis.

Exploring the synthetic approaches and clinical prowess of established macrocyclic pharmaceuticals

Macrocyclic compounds, characterized by cyclic structures, often originate from either modified forms of unicyclic canonical molecules or natural products. Within the field of medicinal chemistry, there has been a growing fascination with drug-like macrocycles in recent years, primarily due to compelling evidence indicating that macrocyclization can significantly influence both the biological and physiochemical properties, as well as the selectivity, when compared to their acyclic counterparts. The approval of contemporary pharmaceutical agents like Lorlatinib underscore the notable clinical relevance of drug-like macrocycles. Nonetheless, the synthesis of these drug-like macrocycles poses substantial challenges, primarily stemming from the complexity of ring-closing reactions, which are inherently dependent on the size and geometry of the bridging linker, impacting overall yields. Nevertheless, macrocycles offer a promising avenue for expanding the synthetic toolkit in medicinal chemistry, enabling the creation of bioactive compounds. To shed light on the subject, we delve into the clinical prowess of established macrocyclic drugs, spanning various therapeutic areas, including oncology, and infectious diseases. Case studies of clinically approved macrocyclic agents illustrate their profound impact on patient care and disease management. As we embark on this journey through the world of macrocyclic pharmaceuticals, we aim to provide a comprehensive overview of their synthesis and clinical applications, shedding light on the pivotal role they play in modern medicine.