Daniel Hamza

Expansion of chemical space for collaborative lead generation and drug discovery: the European Lead Factory Perspective

High-throughput screening (HTS) represents a major cornerstone of drug discovery. The availability of an innovative, relevant and high-quality compound collection to be screened often dictates the final fate of a drug discovery campaign. Given that the chemical space to be sampled in research programs is practically infinite and sparsely populated, significant efforts and resources need to be invested in the generation and maintenance of a competitive compound collection. The European Lead Factory (ELF) project is addressing this challenge by leveraging the diverse experience and know-how of academic groups and small and medium enterprises (SMEs) engaged in synthetic and/or medicinal chemistry. Here, we describe the novelty, diversity, structural complexity, physicochemical characteristics and overall attractiveness of this first batch of ELF compounds for HTS purposes.

Combining two-directional synthesis and tandem reactions. Part 21: Exploitation of a dimeric macrocycle for chain terminus differentiation and synthesis of an sp3-rich library

The application of a tandem condensation/cyclisation/[3+2]-cycloaddition/elimination reaction gives an sp(3)-rich tricyclic pyrazoline scaffold with two ethyl esters in a single step from a simple linear starting material. The successive hydrolysis and cyclisation (with Boc anhydride) of these 3-dimensional architectures, generates unprecedented 16-membered macrocyclic bisanhydrides (characterised by XRD). Selective amidations could then be achieved by ring opening with a primary amine followed by HATU-promoted amide coupling to yield an sp(3)-rich natural product-like library.

Synthesis of a hexahydropyrrolo indole (HPI) compound library

Scaffolds of natural products represent promising starting points for the development of focused compound libraries. Here, we describe the development of a synthetic route to a compound library based on the hexahydropyrrolo indole (HPI) scaffold, the denoting structural motif of the HPI natural product family. To this end, a two-step approach consisting of a batch synthesis of an advanced functionalizable HPI intermediate followed by the establishment of reaction conditions that allow derivatization of this scaffold at three different positions is described. Subsequently, the optimized methods were applied to the synthesis of a 276-member library.

Synthesis of 4-aminotetrahydropyran scaffolds for drug discovery

Functionalised tetrahydropyran scaffolds were prepared using a tethered enol-ether Prins cyclisation and elaborated to show their potential use in library synthesis. The key 4-hydroxytetrahydropyran scaffold could be readily manipulated to the 4-azidotetrahydropyran that could be elaborated via copper catalysed azide-alkyne cycloaddition or by reduction to the amine, to provide sp3-rich scaffolds useful for drug discovery.

Expedient synthesis of an atypical oxazolidinone compound library

In order to address the current downturn in the drug discovery pipeline, initiatives are being undertaken to synthesise screening libraries of sp3-rich, low molecular weight compounds. As part of the European Lead Factory initiative, the synthesis and derivatisation of a simple hexahydrooxazolo[5,4-c]pyridin-2(1H)-one bicyclic carbamate has been achieved. The synthetic route employed involved a telescoped hetero-Diels-Alder/[2,3]-sigmatropic rearrangement/cyclisation sequence to deliver the desired core scaffold containing two points for further diversification. When applied, this synthesis was found to be robust and scalable which allowed the production of a 155 compound library.

Densely functionalised spirocyclic oxetane-piperidine scaffolds for drug discovery

A spirocyclic, sp3-atom rich oxetane-containing scaffold was synthesised in just two steps via a gold catalysed propargylic alcohol rearrangement. The key gold cyclisation can be undertaken on a 40 g scale allowing the preparation of 419 lead-like compounds based on the scaffold for the European Lead Factory.

Diastereoselective Synthesis of Highly Substituted, Amino‐ and Pyrrolidino‐Tetrahydrofurans as Lead‐Like Molecular Scaffolds

A series of highly substituted tetrahydrofurans (THFs), decorated with modifiable 2-aryl, 3-carboxy and 4-amino substituents, has been prepared for biological evaluation within the European Lead Factory. Diastereoselective reductive amination of pre-functionalised 4-oxofurans, readily prepared from cinnamate esters via oxa-Michael/Dieckmann annulation, provided the requisite THF cores on gram scale with three contiguous stereocentres, including full substitution at C-3. In a second series, a pyrrolidine ring was fused to the same oxofuran scaffold via an intramolecular reductive amination, inverting the configuration at C-4 relative to the other ring substituents. The resulting compounds, which displayed desirable physical properties as lead-like scaffolds, were derivatised into a small library of 24 compounds, demonstrating their ability to serve as starting points for drug discovery. Ultimately, this chemistry enabled the preparation of 1948 THF-containing compounds for inclusion in the Joint European Compound Library.