Preparation of Structurally Diverse Compounds from the Natural Product Lycorine

Identification of a Selective Anticancer Agent from a Collection of Complex-And-Diverse Compounds Synthesized from Stevioside

Compounds constructed by distorting the ring systems of natural products serve as a ready source of complex and diverse molecules, useful for a variety of applications. Herein is presented the use of the diterpenoids steviol and isosteviol as starting points for the construction of >50 new compounds through this complexity-to-diversity approach, featuring novel ring system distortions and a noteworthy thallium(III) nitrate (TTN)-mediated ring fusion. Evaluation of this collection identified SteviX4 as a potent and selective anticancer compound, inducing cell death at low nanomolar concentrations against some cancer cell lines in culture, compared to micromolar activity against others. SteviX4 induces ferroptotic cell death in susceptible cell lines, and target identification experiments reveal SteviX4 acts as an inhibitor of glutathione peroxidase 4 (GPX4), a critical protein that protects cancer cells against ferroptosis. In its induction of cell death, SteviX4 displays enhanced cell line selectivity relative to most known GPX4 inhibitors. SteviX4 was used to reveal dependency on GPX4 as a vulnerability of certain cancer cell lines, not tied to any one type of cancer, suggesting GPX4 inhibition as a cancer type-agnostic anticancer strategy. With its high fraction of sp3-hybridized carbons and considerable cell line selectivity and potency, SteviX4 is unique among GPX4 inhibitors, serving as an outstanding probe compound and basis for further translational development.

Chloroformate-mediated ring cleavage of indole alkaloids leads to re-engineered antiplasmodial agents

Natural product ring distortion strategies have enabled rapid access to unique libraries of stereochemically complex compounds to explore new chemical space and increase our understanding of biological processes related to human disease. Herein is described the development of a ring-cleavage strategy using the indole alkaloids yohimbine, apovincamine, vinburnine, and reserpine that were reacted with a diversity of chloroformates paired with various alcohol/thiol nucleophiles to enable the rapid synthesis of 47 novel small molecules. Ring cleavage reactions of yohimbine and reserpine produced two diastereomeric products in moderate to excellent yields, whereas apovincamine and vinburnine produced a single diastereomeric product in significantly lower yields. Free energy calculations indicated that diastereoselectivity regarding select ring cleavage reactions from yohimbine and apovincamine is dictated by the geometry and three-dimensional structure of reactive cationic intermediates. These compounds were screened for antiplasmodial activity due to the need for novel antimalarial agents. Reserpine derivative 41 was found to exhibit interesting antiplasmodial activities against Plasmodium falciparum parasites (EC50 = 0.50 μM against Dd2 cultures), while its diastereomer 40 was found to be three-fold less active (EC50 = 1.78 μM). Overall, these studies demonstrate that the ring distortion of available indole alkaloids can lead to unique compound collections with re-engineered biological activities for exploring and potentially treating human disease.

Short Formal Syntheses of Lycorine and Congeners Using a 5-Endo-Trig/6-Endo-Trig Radical Cyclization Sequence

Here, we report a practical route to medicinally interesting lycorine congeners alongside formal syntheses of various lycorine-type natural products, including lycorine itself. The efficiency of our strategy derives from a back-to-back 5-endo-trig/6-endo-trig radical cyclization sequence, which we systematically studied both experimentally and computationally. The results of our work will facilitate future development of urgently needed antiviral therapeutics based on lycorine.

Lycorine and homolycorine derivatives for chemo-sensitizing resistant human ovarian adenocarcinoma cells

BACKGROUND

Multidrug resistance is the major obstacle to cancer chemotherapy. Modulation of P-glycoprotein and drug combination approaches have been considered important strategies to overcome drug resistance.

PURPOSE

Aiming at generating a small library of Amaryllidaceae-type alkaloids to overcome drug resistance, two major alkaloids, isolated from Pancratium maritimum, lycorine (1), and 2α-10bα-dihydroxy-9-O-demethylhomolycorine (2), were derivatized, giving rise to nineteen derivatives (3 - 21).

METHODS

The main chemical transformation of lycorine resulted from the cleavage of ring E of the diacetylated lycorine derivative (3) to obtain compounds that have carbamate and amine functions (5 - 16), while acylation of compound 2 provided derivatives 17 - 21. Compounds 1 - 21 were evaluated for their effects on cytotoxicity, and drug resistance reversal, using resistant human ovarian carcinoma cells (HOC/ADR), overexpressing P-glycoprotein (P-gp/ABCB1), as model.

RESULTS

Excluding lycorine (1) (IC50 values of 1.2- 2.5 µM), the compounds were not cytotoxic or showed moderate/weak cytotoxicity. Chemo-sensitization assays were performed by studying the in vitro interaction between the compounds and the anticancer drug doxorubicin. Most of the compounds have shown synergistic interactions with doxorubicin. Compounds 5, 6, 9 - 14, bearing both carbamate and aromatic amine moieties, were found to have the highest sensitization rate, reducing the dose of doxorubicin 5-35 times, highlighting their potential to reverse drug resistance in combination chemotherapy. Selected compounds (4 - 6, 9 - 14, and 21), able of re-sensitizing resistant cancer cells, were further evaluated as P-gp inhibitors. Compound 11, which has a para‑methoxy-N-methylbenzylamine moiety, was the strongest inhibitor. In the ATPase assay, compounds 9-11 and 13 behaved as verapamil, suggesting competitive inhibition of P-gp. At the same time, none of these compounds affected P-gp expression at the mRNA or protein level.

CONCLUSIONS

This study provided evidence of the potential of Amaryllidaceae alkaloids as lead candidates for the development of MDR reversal agents.

Influence of Sucrose and Activated Charcoal on Phytochemistry and Vegetative Growth in Zephyranthes irwiniana (Ravenna) Nic. García (Amaryllidaceae)

Zephyranthes irwiniana (Ravenna) Nic. García is an endemic, red list threatened species from the Brazilian savanna (Cerrado) with pharmacological potential to treat the symptoms of Alzheimer's Disease (AD). This work analyzed the vegetative growth and phytochemistry of its potential compounds, in response to variations in sucrose concentration and activated carbon (AC). Seeds were germinated in vitro and in the greenhouse. The in vitro bulbs were separated in six treatments with different sucrose concentrations (30, 45 and 60 gL-1) and/or AC (1 gL-1). Biomass increases in individuals grown in the greenhouse were higher than those cultivated in vitro. Sucrose concentration significantly increased biomass and root number. AC had a positive influence on leaf and root size, and a negative influence on root number. GC-MS analyses indicated great variation in the abundance of α-terpenyl-acetate, ethyl linoleate, clionasterol and lycorine between treatments, with maximum concentrations of 53.06%, 38.68, 14.34% and 2.57%, respectively. Histolocalization tests indicated the presence of alkaloids in the leaf chlorenchyma and bulb cataphylls. Finally, the present study provided new evidence that the constitution of the culture medium directly influences the vegetative growth and phytochemistry of this species, providing a good medium condition for propagating the species under threat.

V, Agianian B, Garcia Chavez M, Vudatha V, Wang R, Vangipurapu R, Chen L, Kennedy P, Subramanian K, Quirke JC, Beato F, Underwood PW, Fleming JB, Trevino J, Hergenrother PJ, Gavathiotis E, Sebti SM. Discovery of KRB-456, a KRAS G12D Switch-I/II Allosteric Pocket Binder That Inhibits the Growth of Pancreatic Cancer Patient-derived Tumors

Currently, there are no clinically approved drugs that directly thwart mutant KRAS G12D, a major driver of human cancer. Here, we report on the discovery of a small molecule, KRB-456, that binds KRAS G12D and inhibits the growth of pancreatic cancer patient-derived tumors. Protein nuclear magnetic resonance studies revealed that KRB-456 binds the GDP-bound and GCP-bound conformation of KRAS G12D by forming interactions with a dynamic allosteric binding pocket within the switch-I/II region. Isothermal titration calorimetry demonstrated that KRB-456 binds potently to KRAS G12D with 1.5-, 2-, and 6-fold higher affinity than to KRAS G12V, KRAS wild-type, and KRAS G12C, respectively. KRB-456 potently inhibits the binding of KRAS G12D to the RAS-binding domain (RBD) of RAF1 as demonstrated by GST-RBD pulldown and AlphaScreen assays. Treatment of KRAS G12D-harboring human pancreatic cancer cells with KRB-456 suppresses the cellular levels of KRAS bound to GTP and inhibits the binding of KRAS to RAF1. Importantly, KRB-456 inhibits P-MEK, P-AKT, and P-S6 levels in vivo and inhibits the growth of subcutaneous and orthotopic xenografts derived from patients with pancreatic cancer whose tumors harbor KRAS G12D and KRAS G12V and who relapsed after chemotherapy and radiotherapy. These results warrant further development of KRB-456 for pancreatic cancer.

SIGNIFICANCE

There are no clinically approved drugs directly abrogating mutant KRAS G12D. Here, we discovered a small molecule, KRB-456, that binds a dynamic allosteric binding pocket within the switch-I/II region of KRAS G12D. KRB-456 inhibits P-MEK, P-AKT, and P-S6 levels in vivo and inhibits the growth of subcutaneous and orthotopic xenografts derived from patients with pancreatic cancer. This discovery warrants further advanced preclinical and clinical studies in pancreatic cancer.

Sanguinarine Exhibits Antiviral Activity against Porcine Reproductive and Respiratory Syndrome Virus via Multisite Inhibition Mechanisms

Porcine reproductive and respiratory syndrome virus (PRRSV), the etiological agent of PRRS, is prevalent worldwide, causing substantial and immense economic losses to the global swine industry. While current commercial vaccines fail to efficiently control PRRS, the development of safe and effective antiviral drugs against PRRSV is urgently required. Alkaloids are natural products with wide pharmacological and biological activities. Herein, sanguinarine, a benzophenanthridine alkaloid that occurs in many plants such as Macleaya cordata, was demonstrated as a potent antagonist of PRRSV. Sanguinarine attenuated PRRSV proliferation by targeting the internalization, replication, and release stages of the viral life cycle. Furthermore, ALB, AR, MAPK8, MAPK14, IGF1, GSK3B, PTGS2, and NOS2 were found as potential key targets related to the anti-PRRSV effect of sanguinarine as revealed by network pharmacology and molecular docking. Significantly, we demonstrated that the combination of sanguinarine with chelerythrine, another key bioactive alkaloid derived from Macleaya cordata, improved the antiviral activity. In summary, our findings reveal the promising potential of sanguinarine as a novel candidate for the development of anti-PRRSV agents.

Recent ring distortion reactions for diversifying complex natural products

Covering: 2013-2022.Chemical diversification of natural products is an efficient way to generate natural product-like compounds for modern drug discovery programs. Utilizing ring-distortion reactions for diversifying natural products would directly alter the core ring systems of small molecules and lead to the production of structurally complex and diverse compounds for high-throughput screening. We review the ring distortion reactions recently used in complexity-to-diversity (CtD) and pseudo natural products (pseudo-NPs) strategies for diversifying complex natural products. The core ring structures of natural products are altered via ring expansion, ring cleavage, ring edge-fusion, ring spiro-fusion, ring rearrangement, and ring contraction. These reactions can rapidly provide natural product-like collections with properties suitable for a wide variety of biological and medicinal applications. The challenges and limitations of current ring distortion reactions are critically assessed, and avenues for future improvements of this rapidly expanding field are discussed. We also provide a toolbox for chemists for the application of ring distortion reactions to access natural product-like molecules.

Target-Agnostic P-Glycoprotein Assessment Yields Strategies to Evade Efflux, Leading to a BRAF Inhibitor with Intracranial Efficacy

The blood-brain barrier (BBB) presents a major hurdle in the development of central nervous system (CNS) active therapeutics, and expression of the P-glycoprotein (P-gp) efflux transporter at the blood-brain interface further impedes BBB penetrance of most small molecules. Designing efflux liabilities out of compounds can be laborious, and there is currently no generalizable approach to directly transform periphery-limited agents to ones active in the CNS. Here, we describe a target-agnostic, prospective assessment of P-gp efflux using diverse compounds. Our results demonstrate that reducing the molecular size or appending a carboxylic acid in many cases enables evasion of P-gp efflux in cell-based experiments and in mice. These strategies were then applied to transform a periphery-limited ^V600EBRAF inhibitor, dabrafenib, into versions that possess potent and selective anti-cancer activity but now also evade P-gp-mediated efflux. When compared to dabrafenib, the compound developed herein (everafenib) has superior BBB penetrance and superior efficacy in an intracranial mouse model of metastatic melanoma, suggesting it as a lead candidate for the treatment of melanoma metastases to the brain and gliomas with BRAF mutation. More generally, the results described herein suggest the actionability of the trends observed in these target-agnostic efflux studies and provide guidance for the conversion of non-BBB-penetrant drugs into versions that are BBB-penetrant and efficacious.

Transition-Metal-Free Synthesis of 4-Amino Isoquinolin-1(2H)-ones via Tandem Reaction of Arynes and Oxazoles

A facile and transition-metal-free method for the synthesis of 4-amino isoquinolin-1(2H)-ones has been developed. Arynes react with 4, 5-disubstituted oxazoles through a tandem Diels-Alder reaction/dehydrogenation-aromatization/tautamerization process to produce 4-amino isoquinolin-1(2H)-ones...

CtD strategy to construct stereochemically complex and structurally diverse compounds from griseofulvin

The Complexity to Diversity (CtD) strategy, a strategy for the synthesis of stereochemically complex and structurally diverse small molecules from natural products using ring-distortion reactions, was applied in the synthesis of a 47-member compound collection from the natural product griseofulvin. A Tsuji-Trost allylation and oxa-Michael cyclization tandem reaction was used for the first time in the CtD strategy to generate complex ring fused compounds.

Ring Distortion of Vincamine Leads to the Identification of Re-Engineered Antiplasmodial Agents

There is a significant need for new agents to combat malaria, which resulted in ∼409,000 deaths globally in 2019. We utilized a ring distortion strategy to create complex and diverse compounds from vincamine with the goal of discovering molecules with re-engineered biological activities. We found compound 8 (V3b) to target chloroquine-resistant Plasmodium falciparum Dd2 parasites (EC₅₀ = 1.81 ± 0.09 μM against Dd2 parasites; EC₅₀ > 40 μM against HepG2 cells) and established structure-activity relationships for 25 related analogues. New analogue 30 (V3ss, Dd2, EC₅₀ = 0.25 ± 0.004 μM; HepG2, EC₅₀ > 25 μM) was found to demonstrate the most potent activity, which prevents exit on the parasite from the schizont stage of intraerythrocytic development and requires >24 h to kill P. falciparum Dd2 cells. These findings demonstrate the potential that vincamine ring distortion has toward the discovery of novel antimalarial agents and other therapies significant to human health.

Limonin as a Starting Point for the Construction of Compounds with High Scaffold Diversity

Structurally complex natural products have been a fruitful source for the discovery and development of new drugs. In an effort to construct a compound collection populated by architecturally complex members with unique scaffolds, we have used the natural product limonin as a starting point. Limonin is an abundant triterpenoid natural product and, through alteration of its heptacyclic core ring system using short synthetic sequences, a collection of 98 compounds was created, including multiple members with novel ring systems. The reactions leveraged in the construction of these compounds include novel ring cleavage, rearrangements, and cyclizations, and this work is highlighted by the discovery of a novel B-ring cleavage reaction, a unique B/C-ring rearrangement, an atypical D-ring cyclization, among others. Computational analysis shows that 52 different scaffolds/ring systems were produced during the course of this work, of which 36 are unprecedented. Phenotypic screening and structure-activity relationships identified compounds with activity against a panel of cancer cell lines.

Hexadehydro-Diels-Alder Reaction: Benzyne Generation via Cycloisomerization of Tethered Triynes

The hexadehydro-Diels-Alder (HDDA) reaction is the thermal cyclization of an alkyne and a 1,3-diyne to generate a benzyne intermediate. This is then rapidly trapped, in situ, by a variety of species to yield highly functionalized benzenoid products. In contrast to nearly all other methods of aryne generation, no other reagents are required to produce an HDDA benzyne. The versatile and customizable nature of the process has attracted much attention due not only to its synthetic potential but also because of the fundamental mechanistic insights the studies often afford. The authors have attempted to provide here a comprehensive compilation of publications appearing by mid-2020 that describe experimental results of HDDA reactions.

Re-engineering natural products to engage new biological targets

Covering: up to 2020 Natural products have a long history in drug discovery, with their inherent biological activity often tailored by medicinal chemists to arrive at the final drug product. This process is illustrated by numerous examples, including the conversion of epothilone to ixabepilone, erythromycin to azithromycin, and lovastatin to simvastatin. However, natural products are also fruitful starting points for the creation of complex and diverse compounds, especially those that are markedly different from the parent natural product and accordingly do not retain the biological activity of the parent. The resulting products have physiochemical properties that differ considerably when compared to traditional screening collections, thus affording an opportunity to discover novel biological activity. The synthesis of new structural frameworks from natural products thus yields value-added compounds, as demonstrated in the last several years with multiple biological discoveries emerging from these collections. This Highlight details a handful of these studies, describing new compounds derived from natural products that have biological activity and cellular targets different from those evoked/engaged by the parent. Such re-engineering of natural products offers the potential for discovering compounds with interesting and unexpected biological activity.

Pseudo-natural products and natural product-inspired methods in chemical biology and drug discovery

Through evolution, nature has provided natural products (NPs) as a rich source of diverse bioactive material. Many drug discovery programs have used nature as an inspiration for the design of NP-like compound classes. These concepts are guided by the prevalidated biological relevance of NPs while going beyond the limitations of nature to produce chemical matter that could have unexpected or novel bioactivities. Herein, we discuss, compare, and highlight recent examples of NP-inspired methods with a focus on the pseudo-NP concept.

Preventing Morphine-Seeking Behavior through the Re-Engineering of Vincamine's Biological Activity

Innovative discovery strategies are essential to address the ongoing opioid epidemic in the United States. Misuse of prescription and illegal opioids (e.g., morphine, heroin) has led to major problems with addiction and overdose. We used vincamine, an indole alkaloid, as a synthetic starting point for dramatic structural alterations of its complex, fused ring system to synthesize 80 diverse compounds with intricate molecular architectures. A select series of vincamine-derived compounds were screened for both agonistic and antagonistic activities against a panel of 168 G protein-coupled receptor (GPCR) drug targets. Although vincamine was without an effect, the novel compound 4 (V2a) demonstrated antagonistic activities against hypocretin (orexin) receptor 2. When advanced to animal studies, 4 (V2a) significantly prevented acute morphine-conditioned place preference (CPP) and stress-induced reinstatement of extinguished morphine-CPP in mouse models of opioid reward and relapse. These results demonstrate that the ring distortion of vincamine offers a promising way to explore new chemical space of relevance to opioid addiction.

Biodegradation of ritalinic acid by Nocardioides sp. - Novel imidazole-based alkaloid metabolite as a potential marker in sewage epidemiology

The consumption of methylphenidate, a nootropic drug used to improve mental performance, is becoming increasingly serious. Methylphenidate is metabolized in human liver to ritalinic acid, which has been commonly detected in sewage and surface waters. Additionally, ritalinic acid serves as a biomarker in sewage epidemiology studies. Thus knowledge of the stability and microbial degradation pathways of ritalinic acid is essential for proper estimation of methylphenidate consumption. In the study reported here, we describe the fast formation of a previously unknown, dead-end metabolite of ritalinic acid by Nocardioides sp. strain MW5. HRMS and 2D NMR analyses allowed precisely identification of the compound as an imidazole-based alkaloid cation with chemical formula 11-[3-(formylamino)propyl]-1,2,3,4,6,7,8,9-octahydrodipyrido[1,2-a:1',2'-c]imidazole-5-ium. In experiments, Nocardioides sp. strain MW5 transformed 34% of ritalinic acid into this metabolite, while 52% was mineralized into CO₂. Alkaloid was not biodegraded during the OECD 301 F test. This study provides new insight into the environmental fate of methylphenidate and its metabolites. The data collected are essential for assessing nootropic drug consumption by sewage epidemiology and should lead to a better understanding of microbial degradation of ritalinic acid.

Re-Engineering of Yohimbine's Biological Activity through Ring Distortion: Identification and Structure-Activity Relationships of a New Class of Antiplasmodial Agents

Select natural products are ideal starting points for ring distortion, or the dramatic altering of inherently complex molecules through short synthetic pathways, to generate an array of novel compounds with diverse skeletal architectures. A major goal of our ring distortion approach is to re-engineer the biological activity of indole alkaloids to identify new compounds with diverse biological activities in areas of significance to human health and medicine. In this study, we re-engineered the biological activity of the indole alkaloid yohimbine through ring rearrangement and ring cleavage synthesis pathways to discover new series of antiplasmodial agents. One new compound, Y7j, was found to demonstrate good potency against chloroquine-resistant Plasmodium falciparum Dd2 cells (EC₅₀ = 0.33 μM) without eliciting cytotoxicity against HepG2 cells (EC₅₀ > 40 μM). Y7j demonstrated stage-specific action against parasites at the late ring/trophozoite stage. A series of analogues was synthesized to gain structure-activity relationship insights, and we learned that both benzyl groups of Y7j are required for activity and fine-tuning of antiplasmodial activities could be accomplished by changing substitution patterns on the benzyl moieties. This study demonstrates the potential for ring distortion to drive new discoveries and change paradigms in chemical biology and drug discovery.

Imidazotetrazines as Weighable Diazomethane Surrogates for Esterifications and Cyclopropanations

Diazomethane is one of the most versatile reagents in organic synthesis, but its utility is limited by its hazardous nature. Although alternative methods exist to perform the unique chemistry of diazomethane, these suffer from diminished reactivity and/or correspondingly harsher conditions. Herein, we describe the repurposing of imidazotetrazines (such as temozolomide, TMZ, the standard of care for glioblastoma) for use as synthetic precursors of alkyl diazonium reagents. TMZ was employed to conduct esterifications and metal-catalyzed cyclopropanations, and results show that methyl ester formation from a wide variety of substrates is especially efficient and operationally simple. TMZ is a commercially available solid that is non-explosive and non-toxic, and should find broad utility as a replacement for diazomethane.

One pot synthesis of pyrrolo[3,2,1-de]phenanthridines from 7-phenylindoles via tandem C–H olefination/aza-Michael addition

An unprecedented one-pot C–H olefination/aza-Michael addition tandem process has been developed for the synthesis of pyrrolo[3,2,1-de]phenanthridines from 7-phenylindoles and alkenes using a [Cp*RhCl₂]₂/AgOAc/Me₄NOAc catalytic system.

Guided by evolution: from biology oriented synthesis to pseudo natural products

This review provides an overview and historical context to two concepts for the design of natural product-inspired compound libraries and highlights the used synthetic methodologies.

Diverse compounds from pleuromutilin lead to a thioredoxin inhibitor and inducer of ferroptosis

The chemical diversification of natural products provides a robust and general method for the creation of stereochemically rich and structurally diverse small molecules. The resulting compounds have physicochemical traits different from those in most screening collections, and as such are an excellent source for biological discovery. Herein, we subject the diterpene natural product pleuromutilin to reaction sequences focused on creating ring system diversity in few synthetic steps. This effort resulted in a collection of compounds with previously unreported ring systems, providing a novel set of structurally diverse and highly complex compounds suitable for screening in a variety of different settings. Biological evaluation identified the novel compound ferroptocide, a small molecule that rapidly and robustly induces ferroptotic death of cancer cells. Target identification efforts and CRISPR knockout studies reveal that ferroptocide is an inhibitor of thioredoxin, a key component of the antioxidant system in the cell. Ferroptocide positively modulates the immune system in a murine model of breast cancer and will be a useful tool to study the utility of pro-ferroptotic agents for treatment of cancer.

Diverse compounds from pleuromutilin lead to a thioredoxin inhibitor and inducer of ferroptosis

The chemical diversification of natural products provides a robust and general method for the creation of stereochemically rich and structurally diverse small molecules. The resulting compounds have physicochemical traits different from those in most screening collections, and as such are an excellent source for biological discovery. Herein, we subject the diterpene natural product pleuromutilin to reaction sequences focused on creating ring system diversity in few synthetic steps. This effort resulted in a collection of compounds with previously unreported ring systems, providing a novel set of structurally diverse and highly complex compounds suitable for screening in a variety of different settings. Biological evaluation identified the novel compound ferroptocide, a small molecule that rapidly and robustly induces ferroptotic death of cancer cells. Target identification efforts and CRISPR knockout studies reveal that ferroptocide is an inhibitor of thioredoxin, a key component of the antioxidant system in the cell. Ferroptocide positively modulates the immune system in a murine model of breast cancer and will be a useful tool to study the utility of pro-ferroptotic agents for treatment of cancer.

Recent Progress in Natural-Product-Inspired Programs Aimed To Address Antibiotic Resistance and Tolerance

Bacteria utilize multiple mechanisms that enable them to gain or acquire resistance to antibiotic therapies during the treatment of infections. In addition, bacteria form biofilms which are surface-attached communities of enriched populations containing persister cells encased within a protective extracellular matrix of biomolecules, leading to chronic and recurring antibiotic-tolerant infections. Antibiotic resistance and tolerance are major global problems that require innovative therapeutic strategies to address the challenges associated with pathogenic bacteria. Historically, natural products have played a critical role in bringing new therapies to the clinic to treat life-threatening bacterial infections. This Perspective provides an overview of antibiotic resistance and tolerance and highlights recent advances (chemistry, biology, drug discovery, and development) from various research programs involved in the discovery of new antibacterial agents inspired by a diverse series of natural product antibiotics.