Rutaecarpine-inspired scaffold-hopping strategy and Ullmann cross-coupling based synthetic approach: Identification of pyridopyrimidinone-indole based novel anticancer chemotypes.

Natural products as starting templates have shown historically major contribution to development of drugs. Inspired by the structure-function of an anticancer natural alkaloid Rutaecarpine, the Scaffold-hopped Acyclic Analogues of Rutaecarpine (SAAR) with 'N'-atom switch (1°-hop) and ring-opening (2°-hop) were investigated. A new synthetic route was developed for an effective access to the analogues, i.e. 2-indolyl-pyrido[1,2-a]pyrimidinones, which involved preparation of N-Boc-N'-phthaloyltryptamine/mexamine-bromides and pyridopyrmidinon-2-yl triflate, a nickel/palladium-catalysed Ullmann cross-coupling of these bromides and triflate, deprotection of phthalimide followed by N-aroylation, and Boc-deprotection. Fourteen novel SAAR-compounds were prepared, and they showed characteristic antiproliferative activity against various cancer cells. Three most active compounds (11a, 11b, and 11c) exhibited good antiproliferative activity, IC50 7.7-15.8 µM against human breast adenocarcinoma cells (MCF-7), lung cancer cells (A549), and colon cancer cells (HCT-116). The antiproliferative property was also observed in the colony formation assay. The SAAR compound 11b was found to have superior potency than original natural product Rutaecarpine and an anticancer drug 5-FU in antiproliferative activities with relatively lower cytotoxicity towards normal breast epithelial cells (MCF10A) and significantly higher inhibitory effect on cancer cells' migration. The compound 11b was found to possess favourable in silico physicochemical characteristics (lipophilicity-MLOGP, TPSA, and water solubility-ESOL, and others), bioavailability score, and pharmacokinetic properties (GI absorption, BBB non-permeant, P-gp, and CYP2D6). Interestingly, the compound 11b did not show any medicinal chemistry structural alert of PAINS and Brenk filter. The study represents for the first time the successful discovery of new potent anticancer chemotypes using Rutaecarpine natural alkaloid as starting template and reaffirms the significance of natural product-inspired scaffold-hopping technique in drug discovery research.

A study of [2 + 2] cycloaddition-retroelectrocyclization in water: observation of substrate-driven transient-nanoreactor-induced new reactivity.

Organic solvents limit [2 + 2] cycloaddition-retroelectrocyclization (CA-RE) in biological fields. We examined the formation of 1,1,4,4-tetracyanobuta-1,3-dienes (TCBDs) through CA-RE reactions and their unusual reactivity to produce N-heterocyclic compounds when the nature of the surfactant and the concentrations were varied in the aqueous phase. An environment in which transient self-assemblies (vesicles) were induced by the substrate and surfactant molecules initiated new reactivity through H2O addition on the TCBD, generating the enol form of the intermediate, which results in the formation of the 6,6-dicyano-heteropentafulvene (amidofulvene) compound, while lamellar sheets at higher concentrations favored TCBD generation. Interestingly, the amidofulvene underwent a clean transformation to 6-membered heterocycles that resemble cardiotonic drugs (milrinone, amrinone) via keto-enol tautomerism mediated by a polar aprotic solvent, opening up a new avenue for drug discovery. Unlike organic-solvent-mediated CA-RE reactions, the present nanoreactor-mediated approach enabled the selective production of TCBDs as well as new heterocycles using H2O as a green solvent. In addition to the widely explored organic electronics/materials, we believe that this study will help to overcome the long-standing limitation of CA-RE reaction applicability in biological fields.

Molecular medicinal insights into scaffold hopping-based drug discovery success.

In both academia and the pharmaceutical industry, innovative hypotheses, methodologies and technologies that can shorten the drug research and development, leading to higher success rates, are vital. In this review, we demonstrate how innovative variations of the scaffold-hopping strategy have been used to create new druggable molecular spaces, drugs, clinical candidates, preclinical candidates, and bioactive agents. We also analyze molecular modulations that enabled improvements of the pharmacodynamic (PD), physiochemical, and pharmacokinetic (PK) properties (P3 properties) of the drugs resulting from these scaffold-hopping strategies.

A cascade reaction of indolyl-migratory isocyanide insertion, scaffold rearrangement and redox-neutral event with isocyanide as a C(sp3)H-N synthon efficiently constructs indolylisoindolinones.

Herein, we report a Pd(0)-catalyzed cascade reaction of intramolecular indolyl isocyanide-insertion, isocyanide-initiated scaffold-rearrangement with indolyl migration and redox-neutral process, which affords an efficient access to indolylisoindolinones. Isocyanide as a C(sp3)H-N synthon and the alkyl motif of isocyanide as a hydride source have been explored for the first time.

Paradigm shift of "classical" HDAC inhibitors to "hybrid" HDAC inhibitors in therapeutic interventions.

'Epigenetic' regulation of genes via post-translational modulation of proteins is the current mainstay approach for the disease therapies, particularly explored in the Histone Deacetylase (HDAC) class of enzymes. Mainly sight saw in cancer chemotherapeutics, HDAC inhibitors have also found a promising role in other diseases (neurodegenerative disorders, cardiovascular diseases, and viral infections) and successfully entered in various combination therapies (pre-clinical/clinical stages). The prevalent flexibility in the structural design of HDAC inhibitors makes them easily tuneable to merge with other pharmacophore modules for generating multi-targeted single hybrids as a novel tactic to overcome drawbacks of polypharmacy. Herein, we reviewed the putative role of prevalent HDAC hybrids inhibitors in the current and prospective stage as a translational approach to overcome the limitations of the existing conventional drug candidates (parent molecule) when used either alone (drug resistance, solubility issues, adverse side effects, selectivity profile) or in combination (pharmacokinetic interactions, patient compliance) for treating various diseases.