Tertiary Alcohol- or ?-Hydroxy ?-Lactam-Based HIV-1 Protease Inhibitors : Microwave Applications in Batch and Continuous Flow Organic Synthesis

Abstract: Since the outbreak of the HIV/AIDS pandemic in the 1980s, the disease has cost the lives of over 30 million people, and a further 33 million are currently living with the HIV infection. With the appropriate treatment, HIV/AIDS can today be regarded as a chronic but manageable disease. However, treatment is not available globally and UNAIDS still estimates that there are currently 5000 AIDS-related deaths worldwide per day.HIV protease inhibitors (PIs) constitute one of the fundaments of HIV treatment, and are commonly used in so-called highly active antiretroviral therapy (HAART), together with reverse transcriptase inhibitors. Although there are ten PIs on the market, there is still a need for novel structures. The rapid development of resistant strains, due to the high frequency of mutations, together with the commonly observed adverse effects of the drugs available, illustrate the need to develop new potent structures.Two novel scaffolds were investigated in this work. A tertiary alcohol-containing scaffold comprising a three-carbon tether, and a ?-hydroxy ?-lactam-based scaffold were designed, synthesized and evaluated using enzyme- and cell-based assays. X-ray analyses of inhibitors from each class provided information on inhibitor–protease interactions. The inhibitors containing the tertiary alcohol provided at best an enzymatic inhibition (Ki) of 2.3 nM, and an inhibition in the cell-based assay (EC50) of 0.17 µM. The ?-lactam-based inhibitors exhibited better inhibition than the first series; the best values being Ki = 0.7 nM and EC50 = 0.04 µM.The second part of these studies involved the evaluation of a novel non-resonance continuous-flow microwave instrument. The instrument was validated regarding heating capacity, temperature stability and temperature homogeneity. A number of model reactions were performed with low- and high-microwave-absorbing solvents. It was found that the microwave heating source allowed rapid temperature adjustment, together with easily regulated, flow-dependent reaction times, providing an efficient tool for reaction optimisation.