Since thiophene very often yields compounds that are analogous to benzene derivatives in general physiological properties, it was decided to attempt to prepare the nitro and amino derivatives of 1,1,1-trichloro-2,2-bis-(2-thienyl)-ethane (V) as well as the nitro and amino derivatives of 2,2,3-trichloro-1,1-bis-(2-thienyl)-butane (VI).

Gastrointestinal malignancies such as liver and pancreatic cancers are the deadliest due to late detection and drug resistance. Nucleoside analogues, like Gemcitabine, are the conventional therapy despite their little impact on survival and off-target toxicity. A novel class of nucleoside analogues able to evade drug resistance mechanisms has been developed by the Guindon group and biologically screened in our lab. Some of these proprietary molecules were further equipped with a lipoate moiety designed to target cancer cell metabolism. LCB2151 and LCB2179 have emerged as the lead molecules in this class, with an IC50 of 10-15 µM in the Gemcitabine-resistant human pancreatic (Capan-2 & Panc-1) cancer cell lines. The focus of this project is deciphering the cellular mechanisms activated by LCB2151 in these pancreatic cancer lines. A series of biased molecular approaches, like gene expression profiling, and unbiased large throughput proteomic and metabolomics analyses were applied to identify potential targets and affected pathways. Results collectively show that LCB2151 evades drug resistance mechanisms, increases pro-apoptotic markers and impairs mitochondrial respiration as early as 6 hours posttreatment. Furthermore, MS/MS analyses reveal that LCB2151 alters the levels of several metabolites in the central carbon metabolism pathway and identifies the citric acid cycle enzyme α-ketoglutarate dehydrogenase as a potential molecular target of LCB2151. Understanding the exact mechanism of action of our lead molecule along with extensive testing on murine cancer models, will surely pave its way to clinical testing and evaluation.

Ph.d.

Cyclooxygenase (COX) and lipoxygenase (LOX) catalyze the rate-determining step in the production of arachidonic acid- derived signaling molecules (eicosanoids) within the body. COX has been extensively investigated, which has enabled the design of non-steroidal inflammatory drugs (NSAIDs) such as aspirin, acetaminophen (ApAP) and ibuprofen. However, there are still fundamental questions surrounding the LOX family of enzymes, which has limited the development of isoform specific inhibitors. The structural basis and regio- and stereoselectivity of the LOX isoforms are not known. Herein, we describe two strategies to develop isoform-specific inhibitors of lipoxygenase. Efforts were focused on the synthesis of unnatural lipid derivatives, in which the methylene hydrogen atoms on the substrate were replaced with a moiety lacking a labile hydrogen atom, such as fluorine. This would allow the LOX enzyme to remain in an active form, while preventing enzyme turnover. This preliminary work will enable the assessment of their activity as inhibitors and attempts at their co-crystallization might provide the first insight into the binding mode of these fatty acid substrates. The preparation of a small library of acylated 2-aminopyrimidines and their efficacy as inhibitors of soybean lipoxygenase-1 was explored. Preliminary studies suggest the mode of action occurs through a bi-dentate coordination of the ferric iron atom. Modifications of the acylated 2-aminopyrimidines to make it more substrate-like and to increase its lipophilicity, yielded inhibitors with low micromolar IC50 values. With further optimization, acyl 2-aminopyrimidines could serve as a useful platform for the discovery of safe and efficient isoform specific inhibitors.

No description available.

ESKAPE pathogens are notorious in causing nosocomial infections and escaping current antibiotic treatments. There has been a dramatic increase in nosocomial infections accompanied with a decrease in the number of antibiotics developed, leading to significant increase in morbidity and mortality among patients. In an attempt to combat this problem, derivatives of ciprofloxacin, rifabutin and beta-lactam antibiotics were synthesized and tested against the ESKAPE pathogens. From minimum inhibitory concentration assays, 4 ciprofloxacin analogs and 8 beta-lactam analogs were found to be effective against multiple bacterial species. Additionally, 12 rifabutin analogs and 23 beta-lactam analogs were potent against single bacterial species, primarily toward methicillin-resistant Staphylococcus aureus (MRSA) at a concentration of ≤ 25 µg mL-1. Based on the effectiveness against methicillin-resistant Staphylococcus aureus (MRSA), three rifabutin analogs were selected for further testing. Two rifabutin analogs (DU644 and DU645) were found to possess between a one to twofold mean increase of inhibitory activities, while the other rifabutin analogs (DU650) demonstrated up to a twofold decrease of inhibitory activity when compared to the parent drug. These compounds were then examined for their bactericidal and antibiofilm activities against MRSA. From these assays, we found that DU644 and DU645 were 4 times more bactericidal and antibiofilm against MRSA when compared to the parent drug. In addition, rpoB mutation validation results confirmed that modification of these rifabutin derivatives at the C3 and C4 positions, and bearing an imidazolyl ring carrying substituted spiropiperidyl ring, did not change their mechanism of action towards the beta-subunit of RNA polymerase. Cytotoxicity testing performed using human hepatocellular carcinoma epithelial cells (hepG2) showed that at concentrations ranged from 1.25 µg mL-1 to 25 µg mL-1, DU644 and DU645 showed very low toxicity. Collectively, structural drugs modifications of these obsolete drugs are able to restore their antibacterial activities against MRSA, which is notable as the most infectious nosocomial pathogen. Therefore, further development and application of rifabutin analogs might be beneficial for medical use to combat MRSA infections.

No description available.

Ph.d.

Ph.d.

The synthesis of substituted non-symmetric tropones has proven to be a considerable synthetic challenge. Particularly, a 3,4,6-tnsubstituted tropone which is required for the total synthesis of CP-225,917 is currently being undertaken by our group. / Two approaches towards the synthesis of substituted tropones are presented. Both utilize linear diene precursors which are closed to 7-membered cycloheptene rings via ring closing metathesis. In the first method, linear precursors are synthesized by addition of nucleophilic substituents to carbonyl groups to form alcohol groups. After forming the cycloheptene ring, the alcohol groups are eliminated to form the tropone. The second method uses an oxidation protocol to form a,(3-unsaturation on either side of a cycloheptenone precursor. An attempt towards the synthesis of the desired tropone required for the CP-225,917 synthesis is also presented. / The methods described here use simple inexpensive starting materials and provide access to tropone substitution not readily available through other means.