Design, Chemical Synthesis and Biological Evaluation of Potential New Antiviral Agents

Acquired Immunodeficiency Syndrome (AIDS) is a disease caused by the Human Immunodeficiency Virus (HIV). Since its discovery in 1981, more than 25 million people died due to this disease. To date, an effective HIV-1 vaccine usable in prophylaxis or in the therapy of humans has not yet been identified. The failures and limited success of HIV vaccines have reinforced the role of chemotherapy and therefore research on the development of effective drugs. Non-nucleoside reverse transcriptase inhibitors (NNRTIs) were the early agents introduced in the therapy and currently they are the most used, based on their concurrent high activity against the virus and low toxicity against human cells. In addition, the rapid development of virus resistance against these types of drugs, needs to find new molecules able to overcome this drawback. My thesis work started from the design of a small library of new molecules, with hybrid structures based on a template deriving from the natural product (+)-calanolide A and the synthetic molecule α-APA, both showing a potent and selective activity against reverse transcriptase. Docking calculation has allowed to select molecules having the best values of interaction energy with the viral enzyme. Chemical synthesis was carried out together with structural characterization by extensive spectroscopic analysis including NMR technique and mass spectrometry. In particular, the synthesis of the amide group present in the structure of some amino-pyrone compounds using the standard method, resulted in the expected N-acylation, but with a C-acyl byproduct. This result has suggested to look further into the study of N,C-acylation selectivity for the ambidentate amino-pyrone moiety, whose reactivity is poorly known. Regioselectivity was investigated under different conditions (organic bases, solvent, acylating agent), also for an enamino-ester taken as a model compound. Experimental procedures were optimized in order to synthesize selectively pure N- and C-acylated compounds. A preliminary enzymatic assay indicated a good activity in the early prepared compounds of the series, promising for the following in vitro tests on HIV infected cells of each molecule in the whole series. In addition, these compounds were tested against other common viruses for human infective pathologies. With the aim of identifying molecules with potential therapeutic applications, the antiviral activity must be related to cytostatic effect, in order to select the ones with a favored selectivity index. Unfortunately, the molecules showed paragonable values in antiviral and cytostatic effects, the latter one not easily predictable neither by the chemical structure, nor by a computational approach. If the drug design by molecular docking has failed in selecting a new scaffold for NNRTIs, the study has driven the interest towards new potential antitumoral molecules showing activity at sub-micromolar concentration against leukemic cell lines. Due to the structural similarity with recently studied antibacterial natural pyrones, the synthetic molecules showing the lowest values of cytotoxicity were investigated in the inhibition of bacterial strains. Some tested compounds have shown a good activity and selectivity against Gram(+) bacteria.