Exploring heterocyclic scaffolds in the development of multi-target anti-Alzheimer and multi-trypanosomatid compounds

The aim of this PhD thesis consists of the synergistic combination of both highly efficient synthetic approaches and molecular modelling tools for the structure-based drug design and synthesis of novel bioactive heterocyclic compounds. The work carried out has followed two main research lines, namely the development of novel disease-modifying anti-Alzheimer agents and still unexplored chemical entities for the treatment of Neglected Tropical Diseases (NTDs). The results obtained have been presented as a compendium of publications and draft manuscripts. In the framework of the anti-Alzheimer research line, first the hit-to-lead optimization of a practically inactive propidium-related compound easily accessed via a Povarov multicomponent reaction (MCR) approach (Di Pietro O. et al. Eur. J. Med. Chem., 2014, 73, 141), and the subsequent molecular hybridization with a 6-chlorotacrine unit through a molecular dynamics-driven tether length optimization, overall led to one of the most potent non-covalent dual binding site acetylcholinesterase inhibitor (AChEI) ever described in the literature (Di Pietro O. et al. Eur. J. Med. Chem., 2014, 84, 107). Second, the combined recourse to the highly versatile click-chemistry strategy, through the well-known Cu-catalyzed azide-alkyne cycloaddition reaction, and convenient computational chemistry tools, allowed the rational design and synthesis of a novel series of 1,4-disubstituted triazole-based propargylamines as irreversible MAO-B inhibitors (draft manuscript) with the perspective to be further linked to a second pharmacophoric moiety to derive novel MTDLs as potential anti-Alzheimer drug candidates. Furthermore, an extensive computation of the BACE-1 apo conformational ensemble by means of combined molecular dynamics technique and Principal Component Analysis (PCA) method, allowed to carry out an exhaustive study of a secondary transient druggable pocket (draft manuscript) and a virtual screening of 500,000 commercially available fragments for further drug discovery purposes. Finally, in the framework of the NTDs research line, 2−4-step sequences involving as the key step an initial Povarov MCR gave easy access to a small library of quinolones and tricyclic heterofused quinolines, which were subjected to phenotypic whole-cell screenings, leading to the individuation of several low micromolar multi-trypanosomatid hit compounds (Di Pietro et al. Eur. J. Med. Chem. 2015, accepted with minor revision)