Bio-inspired Chemical Space Exploration of Terpenoids

Many computational methods are used to expand the open-ended border of chemical spaces. Natural products and their derivatives are an important source for drug discovery, and some algorithms are devoted to rapidly generating pseudo-natural products, while their accessibility and chemical interpretation were often ignored or underestimated, thus hampering experimental synthesis in practice. Herein, a bio-inspired strategy (named TeroGen) is proposed, in which the cyclization and decoration stage of terpenoid biosynthesis were mimicked by meta-dynamics simulations and deep learning models respectively, to explore their chemical space. In the protocol of TeroGen, the synthetic accessibility is validated by reaction energetics (reaction barrier and reaction heat) based on the GFN2-xTB methods. Chemical interpretation is an intrinsic feature as the reaction pathway is bioinspired and triggered by the RMSD-PP method in conjunction with an encoder-decoder architecture. This is quite distinct from conventional library/fragment-based or rule-based strategies, by using TeroGen, new reaction routes are feasibly explored to increase the structural diversity. For example, only a rather limited number of sesterterpenoids in our training set is included in this work, but our TeroGen would predict more than 30000 sesterterpenoids and map out the reaction network with super efficiency, ten times as many as the known sesterterpenoids (less than 2500). In sum, TeroGen not only greatly expands the chemical space of terpenoids but also provides various plausible biosynthetic pathways, which are crucial clues for heterologous biosynthesis, bio-mimic and chemical synthesis of complicated terpenoids.

Structural study of anhydrous and hydrated 5-fluorouracil co-crystals with nicotinamide and isonicotinamide

5-Fluorouracil is a widely used anti-cancer drug which exhibits diverse polymorphic and co-crystalline behavior. Here we report two new solvent-free co-crystals of 5-fluorouracil with model co-formers nicotinamide and isonicotinamide, along with the redetermination of their hydrated analogues. Selected co-formers are categorized as safe and therefore suitable for pharmaceutical applications. Differences and similarities in supramolecular topology of the given structures are discussed. A special emphasis is set on the influence of fluorine moieties on the overall packing and synthetic accessibility of the presented multi-component systems.

Integrating Synthetic Accessibility with AI-based Generative Drug Design

Generative models are frequently used for de novo design in drug discovery projects to propose new molecules. However, the question of whether or not the generated molecules can be synthesized is not systematically taken into account during generation, even though being able to synthesize the generated molecules is a fundamental requirement for such methods to be useful in practice. Methods have been developed to estimate molecule synthesizability, but, so far, there is no consensus on whether or not a molecule is synthesizable. In this paper we introduce the Retro-Score (RScore), which computes a synthetic feasibility score of molecules by performing a full retrosynthetic analysis through our data-driven synthetic planning software Spaya, and its dedicated API: Spaya-API (https://spaya.ai). After a comparison of RScore with other synthetic scores from the literature, we describe a pipeline to generate molecules that validate a list of targets while still being easy to synthesize. We further this idea by performing experiments comparing molecular generator outputs across a range of constraints and conditions. We show that the RScore can be learned by a Neural Network, which leads to a new score: RSPred. We demonstrate that using the RScore or RSPred as a constraint during molecular generation enables to obtain more synthesizable solutions, with higher diversity. The open-source Python code containing all the scores and the experiments can be found on https://github.com/iktos/generation-under-synthetic- constraint.

Integrating Synthetic Accessibility with AI-based Generative Drug Design

Generative models are frequently used for de novo design in drug discovery projects to propose new molecules. However, the question of whether or not the generated molecules can be synthesized is not systematically taken into account during generation, even though being able to synthesize the generated molecules is a fundamental requirement for such methods to be useful in practice. Methods have been developed to estimate molecule synthesizability, but, so far, there is no consensus on whether or not a molecule is synthesizable. In this paper we introduce the Retro-Score (RScore), which computes a synthetic feasibility score of molecules by performing a full retrosynthetic analysis through our data-driven synthetic planning software Spaya, and its dedicated API: Spaya-API (https://spaya.ai). After a comparison of RScore with other synthetic scores from the literature, we describe a pipeline to generate molecules that validate a list of targets while still being easy to synthesize. We further this idea by performing experiments comparing molecular generator outputs across a range of constraints and conditions. We show that the RScore can be learned by a Neural Network, which leads to a new score: RSPred. We demonstrate that using the RScore or RSPred as a constraint during molecular generation enables to obtain more synthesizable solutions, with higher diversity. The open-source Python code containing all the scores and the experiments can be found on https://github.com/iktos/generation-under-synthetic- constraint.

Electrochemically Driven Cross-Electrophile Coupling of Alkyl Halides

Recent research in medicinal chemistry suggests a correlation between an increase in the fraction of sp3 carbons in drug candidates with their improved success rate in clinical trials. As such, the development of robust and selective methods for the construction of C(sp3)-C(sp3) bonds remains a critical problem in modern organic chemistry. Owing to the broad availability and synthetic accessibility of alkyl halides, their direct cross coupling—commonly known as cross-electrophile coupling (XEC)—provides a promising route toward this objective. However, achieving high selectivity in C(sp3)-C(sp3) XEC remains a largely unmet challenge. Herein, we employ electrochemistry to achieve the differential activation of alkyl halides by exploiting their disparate electronic and steric properties. Specifically, the selective cathodic reduction of a more substituted alkyl halide gives rise to a carbanion, which undergoes preferential coupling with a less substituted alkyl halide via bimolecular nucleophilic substitution (SN2) to forge a new C–C bond. This transition-metal free protocol enables the efficient XEC of a variety of functionalized and unactivated alkyl electrophiles and exhibits substantially improved chemoselectivity versus existing methodologies.

Electrochemically Driven Cross-Electrophile Coupling of Alkyl Halides

Recent research in medicinal chemistry suggests a correlation between an increase in the fraction of sp3 carbons in drug candidates with their improved success rate in clinical trials. As such, the development of robust and selective methods for the construction of C(sp3)-C(sp3) bonds remains a critical problem in modern organic chemistry. Owing to the broad availability and synthetic accessibility of alkyl halides, their direct cross coupling—commonly known as cross-electrophile coupling (XEC)—provides a promising route toward this objective. However, achieving high selectivity in C(sp3)-C(sp3) XEC remains a largely unmet challenge. Herein, we employ electrochemistry to achieve the differential activation of alkyl halides by exploiting their disparate electronic and steric properties. Specifically, the selective cathodic reduction of a more substituted alkyl halide gives rise to a carbanion, which undergoes preferential coupling with a less substituted alkyl halide via bimolecular nucleophilic substitution (SN2) to forge a new C–C bond. This transition-metal free protocol enables the efficient XEC of a variety of functionalized and unactivated alkyl electrophiles and exhibits substantially improved chemoselectivity versus existing methodologies.

The Artemiside-Artemisox-Artemisone-M1 Tetrad: Efficacies against Blood Stage P. falciparum Parasites, DMPK Properties, and the Case for Artemiside

Because of the need to replace the current clinical artemisinins in artemisinin combination therapies, we are evaluating fitness of amino-artemisinins for this purpose. These include the thiomorpholine derivative artemiside obtained in one scalable synthetic step from dihydroartemisinin (DHA) and the derived sulfone artemisone. We have recently shown that artemiside undergoes facile metabolism via the sulfoxide artemisox into artemisone and thence into the unsaturated metabolite M1; DHA is not a metabolite. Artemisox and M1 are now found to be approximately equipotent with artemiside and artemisone in vitro against asexual P. falciparum (Pf) blood stage parasites (IC50 1.5–2.6 nM). Against Pf NF54 blood stage gametocytes, artemisox is potently active (IC50 18.9 nM early-stage, 2.7 nM late-stage), although against the late-stage gametocytes, activity is expressed, like other amino-artemisinins, at a prolonged incubation time of 72 h. Comparative drug metabolism and pharmacokinetic (DMPK) properties were assessed via po and iv administration of artemiside, artemisox, and artemisone in a murine model. Following oral administration, the composite Cmax value of artemiside plus its metabolites artemisox and artemisone formed in vivo is some 2.6-fold higher than that attained following administration of artemisone alone. Given that efficacy of short half-life rapidly-acting antimalarial drugs such as the artemisinins is associated with Cmax, it is apparent that artemiside will be more active than artemisone in vivo, due to additive effects of the metabolites. As is evident from earlier data, artemiside indeed possesses appreciably greater efficacy in vivo against murine malaria. Overall, the higher exposure levels of active drug following administration of artemiside coupled with its synthetic accessibility indicate it is much the preferred drug for incorporation into rational new artemisinin combination therapies.

NATURAL ISOTHIOCYANATE ANTI-MALARIA: MOLECULAR DOCKING, PHYSICOCHEMICAL, ADME, TOXICITY AND SYNTHETIC ACCESSIBILITY STUDY OF EUGENOL AND CINNAMALDEHYDE

Objective: This study aims to evaluate novel compounds of isothiocyanate (ITC) based on eugenol and cinnamaldehyde derivatives as the drug candidate of Plasmodium falciparum anti-malaria using in silico method, physicochemical, pharmacokinetics, toxicity, and synthetic accessibility prediction. This present study also describes molecular docking and pharmacoinformatics of natural ITC in Moringa oleifera leaves. Methods: A series of novel ITC compounds (3, 5, and 6) were designed and analyzed with a series of natural ITC compounds (7, 8, 9, 10) for P. falciparum anti-malaria. This research is descriptive qualitative and uses the reverse molecular docking method, proving the biological activity of compounds theoretically using software and database information. Results: Molecular docking study showed that compound 6 exhibits binding affinity (-5.3 Kcal/mol) on Van der Waals interaction with the residual active site (His159, Cys25) of cysteine protease. All designed ITC compounds are obeyed the Lipinski and Veber Rule, have a well-brain penetrant character and have a medium risk for mutagenic, tumorigenic, and reproductive prediction. They are also in the simple rate of synthetic accessibility (SA) estimation. In regards to natural ITCs, they all have better assay characteristics except the SA. Conclusion: Molecular docking, physicochemical, pharmacokinetic, and toxicity studies show that methyl eugenol isothiocyanate and cinnamaldehyde isothiocyanate are promising anti-malaria compounds. Substituents of hydroxy, acetate and tetrahydropyran groups in the building block ring are suggested for better in silico profiles enhancement.

The Artemiside-artemisox-artemisone-M1 Tetrad: Efficacies Against Blood Stage P. falciparum Parasites, DMPK Properties, and the Case for Artemiside

Because of the need to replace the current clinical artemisinins in artemisinin combination therapies, we are evaluating fitness of amino-artemisinins for this purpose. These include the thiomorpholine derivative artemiside obtained in one scalable synthetic step from dihydroartemisinin (DHA) and the derived sulfone artemisone. We have recently shown that artemiside undergoes facile metabolism via the sulfoxide artemisox into artemisone and thence into the unsaturated metabolite M1; DHA is not a metabolite. Artemisox and M1 are now found to be approximately equipotent with artemiside and artemisone in vitro against asexual P. falciparum (Pf) blood stage parasites (IC50 1.5 – 2.6 nM). Against Pf NF54 blood stage gametocytes, artemisox is potently active (IC50 18.9 nM early-stage, 2.7 nM late-stage). Comparative drug metabolism and pharmacokinetic (DMPK) properties were assessed via po and iv administration of artemiside, artemisox and artemisone in a murine model. Following oral administration, the composite Cmax value of artemiside plus its metabolites artemisox and artemisone formed in vivo is some 2.6-fold higher than that attained following administration of artemisone alone. Given that efficacy of short half-life rapidly-acting antimalarial drugs such as the artemisinins is associated with Cmax, it is apparent that artemiside will be more active than artemisone in vivo, due to additive effects of the metabolites. As is evident from earlier data, artemiside indeed possesses appreciably greater efficacy in vivo against murine malaria. Overall, the higher exposure levels of active drug following administration of artemiside coupled with its synthetic accessibility indicate it is much the preferred drug for incorporation into rational new artemisinin combination therapies.