Nearly all clinically used antibiotics have been (1) discovered from microorganisms (2) using phenotype screens to identify inhibitors of bacterial growth. The effectiveness of these antibiotics is attributed to their endogenous roles as bacterial warfare agents against competing microorganisms. Unfortunately, every class of clinically used antibiotic has been met with drug resistant bacteria. In fact, the emergence of resistant bacterial infections coupled to the dismal pipeline of new antibacterial agents has resulted in a global health care crisis. There is an urgent need for innovative antibacterial strategies and treatment options to effectively combat drug resistant bacterial pathogens. Here, we describe the implementation of a Pseudomonas competition strategy, using redox-active phenazines, to identify novel antibacterial leads against Staphylococcus aureus and Staphylococcus epidermidis. In this report, we describe the chemical synthesis and evaluation of a diverse 27-membered phenazine library. Using this microbial warfare inspired approach, we have identified several bromophenazines with potent antibacterial activities against S. aureus and S. epidermidis. The most potent bromophenazine analogue from this focused library demonstrated a minimum inhibitory concentration (MIC) of 0.78-1.56 μM, or 0.31-0.62 μg mL(-1), against S. aureus and S. epidermidis and proved to be 32- to 64-fold more potent than the phenazine antibiotic pyocyanin in head-to-head MIC experiments. In addition to the discovery of potent antibacterial agents against S. aureus and S. epidermidis, we also report a detailed structure-activity relationship for this class of bromophenazine small molecules.

The total synthesis of acortatarin A relying on a Pd(II)-catalyzed spiroketalization is reported. This strategy allows a single stereocenter in the spiroketalization substrate to produce the target efficiently under mild conditions, installing the necessary oxygenation in the backbone through an allylic transposition. The synthesis also verifies that pollenopyrroside B and acortatarin A are the same compound, and electrochemical studies suggest that the reported bioactivity is not due to simple antioxidant properties.

A gold-catalyzed synthesis of cyclic 2-oxodienes from readily prepared propargyl alcohols and the subsequent Diels-Alder reaction are reported. The dehydrative cyclization reactions proceeded smoothly, and the dienes formed in situ were demonstrated to undergo cycloaddition with a variety of dienophiles. This method offers a new strategy for the synthesis of indolocarbazole alkaloids, whereby the convergent synthetic design allows for differentiation between the indole nitrogens.

Thymidylate synthase (TS) inhibitors are an integral component of chemotherapy regimens for difficult to treat cancer subtypes. Despite initial therapeutic benefit, current inhibitors induce TS overexpression or alter folate transport metabolism feedback pathways that tumor cells exploit for drug resistance. Here we report a small molecule TS inhibitor that exhibits i) enhanced antitumor activity as compared to current fluoropyrimidines and antifolates without inducing TS overexpression, ii) is structurally distinct from classical antifolates, iii) extends survival in a pancreatic tumor mouse model, iv) and is well tolerated with equal efficacy using either intraperitoneal or oral administration. Mechanistically, we confirm the compound is a multifunctional non classical antifolate and through a series of analogues identify structural features allowing direct TS inhibition while also maintaining the ability to inhibit dihydrofolate reductase (DHFR). Collectively, this work identifies new non classical antifolate inhibitors that optimize inhibition of thymidylate biosynthesis with a favorable safety profile highlighting potential for enhanced cancer therapy. Citation Format: Maria V. Guijarro, Patrick C. Kellish, Peter E. Dib, Nicholas G. Paciaroni, Akbar Nawab, Jacob Andring, Lidia Kulemina, Nicholas V. Borrero, Carlos Modenutti, Richard L. Bennett, Daniil Shabashvili, Jonathan D. Licht, Robert McKenna, Adrian Roitberg, Robert W. Huigens, Frederic J. Kaye, Maria Zajac-Kaye. First in class multifunctional non classical antifolates inhibits thymidylate synthase and extends survival in pancreatic cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4055.