Anti-influenza activity of diazaadamantanes combined with monoterpene moieties

Antiproliferative in Vitro Evaluation of Terpenic Amines Synthesized via a Rhodium-catalyzed Hydroaminomethylation

Terpene-derived alkaloids show a variety of biological activities, including antioxidant, anti-inflammatory, antimicrobial and cytotoxicity effects. In this work, homologated monoterpene amines have been prepared via a rhodium-catalyzed hydroaminomethylation of biomass-based alkenes, such as (R)-limonene, linalool, myrcene and camphene, in combination with secondary amines of aliphatic and aromatic nature, namely morpholine and N-methylaniline, leading to highly chemo- and regioselective processes. The as-prepared amines were obtained in 50-99 % overall yields, and in vitro tested on a human colon cancer cell line (HCT-116) to evaluate their cytotoxic potential. The lead compound of the series (3 a) showed cytotoxicity in the micromolar range (IC50 52.46 μM) via the induction of cell death by apoptosis, paving the way towards further structure-activity relationship studies.

Tackling Influenza A virus by M2 ion channel blockers: Latest progress and limitations

Influenza outbreaks cause pandemics in millions of people. The treatment of influenza remains a challenge due to significant genetic polymorphism in the influenza virus. Also, developing vaccines to protect against seasonal and pandemic influenza infections is constantly impeded. Thus, antibiotics are the only first line of defense against antigenically distinct strains or new subtypes of influenza viruses. Among several anti-influenza targets, the M2 protein of the influenza virus performs several activities. M2 protein is an ion channel that permits proton conductance through the virion envelope and the deacidification of the Golgi apparatus. Both these functions are critical for viral replication. Thus, targeting the M2 protein of the influenza virus is an essential target. Rimantadine and amantadine are two well-known drugs that act on the M2 protein. However, these drugs acquired resistance to influenza and thus are not recommended to treat influenza infections. This review discusses an overview of anti-influenza therapy, M2 ion channel functions, and its working principle. It also discusses the M2 structure and its role, and the change in the structure leads to mutant variants of influenza A virus. We also shed light on the recently identified compounds acting against wild-type and mutated M2 proteins of influenza virus A. These scaffolds could be an alternative to M2 inhibitors and be developed as antibiotics for treating influenza infections.

Nascent pharmacological advancement in adamantane derivatives

The adamantane moiety has attracted significant attention since its discovery in 1933 due to its remarkable structural, chemical, and medicinal properties. This molecule has a notable impact in the therapeutic field because of its "add-on" lipophilicity to any pharmacophoric moieties. As in the case of molecular hybridization, in which one pharmacophore is attached to another one(s) with a probability of increasing the biological activity, adding an adamantane unit improves the absorption distribution, metabolism and excretion properties of the resultant hybrid molecule. This review summarizes various reports highlighting the biological activities of adamantane-based synthetic compounds and their structure-activity relationship study. The information presented in this review may open up possible dimensions for adamantane-based drug development and discovery in the pharmaceutical industry after proper structural modifications.

Antiviral Compounds to Address Influenza Pandemics: An Update from 2016-2022

In recent decades, the world has gained experience of the dangerous effects of pandemic events caused by emerging respiratory viruses. In particular, annual epidemics of influenza are responsible for severe illness and deaths. Even if conventional influenza vaccines represent the most effective tool for preventing virus infections, they are not completely effective in patients with severe chronic disease and immunocompromised and new small molecules have emerged to prevent and control the influenza viruses. Thus, the attention of chemists is continuously focused on the synthesis of new antiviral drugs able to interact with the different molecular targets involved in the virus replication cycle. To date, different classes of influenza viruses inhibitors able to target neuraminidase enzyme, hemagglutinin protein, Matrix-2 (M2) protein ion channel, nucleoprotein or RNAdependent RNA polymerase have been synthesized using several synthetic strategies comprising the chemical modification of currently used drugs. The best results, in terms of inhibitory activity, are in the nanomolar range and have been obtained from the chemical modification of clinically used drugs such as Peramivir, Zanamivir, Oseltamir, Rimantadine, as well as sialylated molecules, and hydroxypyridinone derivatives. The aim of this review is to report, covering the period 2016-2022, the most recent routes related to the synthesis of effective influenza virus inhibitors.

Azaadamantanes, a New Promising Scaffold for Medical Chemistry

Azaadamantanes are nitrogen-containing analogs of adamantane, which contain one or more nitrogen atoms instead of carbon atoms. This substitution leads to several specific chemical and physical properties. The azaadamantane derivatives have less lipophilicity compared to their adamantane analogs, which affects both their interaction with biological targets and bioavailability. The significant increase in the number of publications during the last decade (2009-2020) concerning the study of reactivity and biological activity of azaadamantanes and their derivatives indicates a great theoretical and practical interest in these compounds. Compounds with pronounced biological activity have been already discovered among azaadamantane derivatives. The review is devoted to the biological activity of azaadamantanes and their derivatives. It presents the main methods for the synthesis of di- and triazaadamantanes and summarizes the accumulated data on studying the biological activity of these compounds. The prospects for the use of azaadamantanes in medical chemistry and pharmacology are discussed.

New type of anti-influenza agents based on benzo[d][1,3]dithiol core

We synthesized a series of amides with a benzo[d][1,3]dithiol core. The chemical library of compounds was tested for their cytotoxicity and inhibiting activity against influenza virus A/California/07/09 (H1N1)pdm09 in MDCK cells. For each compound, values of CC₅₀, IC₅₀ and selectivity index (SI) were determined. Compounds of this structure type were for the first time found to exhibit anti-influenza activity. The structure of an amide substituent in the tested compounds was demonstrated to have a significant effect on their activity against the H1N1 influenza virus and cytotoxicity. Compound 4d has a high selectivity index of about 30. 4d was shown to be most potent at early stages of viral cycle. In direct fusogenic assay it demonstrated dose-dependent activity against fusogenic activity of hemagglutinin of influenza virus. Based on molecular docking and regression analysis data, viral hemagglutinin was suggested as possible target for these new antiviral agents.

Synthesis and Antimicrobial Activity of Adamantyl Substituted Pyridoxine Derivatives

Background:

Adamantane derivatives possess multiple pharmacological activities such as antiviral, anticancer, antimycobacterial, antidiabetic, antiparkinsonian and others. The interest of medicinal chemists in adamantane compounds is due to their unique spatial structure, high lipophilicity, and carbon cage rigidity. As a result, these molecules can easily penetrate biological lipid membranes and often have unique target-specific activity profile. Another pharmacophore studied in this work is pyridoxine (vitamin B6). Pyridoxine plays highly important roles in living cells as a key cofactor of many enzymes. On the other hand, its molecular scaffold is a valuable structural platform which has led to the development of several launched drugs (Pyritinol, Pirisudanol, Cycletanine, Mangafodipir) and a wide number of preclinical and clinical drug candidates.

Objective:

The objective of this study is a synthesis of pyridoxine-adamantane and pyridoxinecyclooctane dipharmacophore molecules. The underlying idea was to assess the antibacterial and antiviral potential of such dipharmacophores, based on multiple examples of promising antiinfective agents which have in their structures adamantane and pyridoxine moieties. Another specific reason was to explore the ability of pyridoxine pharmacophore to suppress the potential of microbial pathogens to develop resistance to drug molecules.

Methods:

In this study, a series of pyridoxine-adamantane and pyridoxine-cyclooctane dipharmacophore molecules were synthesized based on reactions of three different cycloalkyl amines with the corresponding electrophilic derivatives of pyridoxine aldehydes, chlorides and acetates. All synthesized compounds have been tested for their in vitro activity against M. tuberculosis H37Rv strain and H3N2 (A/Aichi/2/68) influenza virus.

Results:

Series of pyridoxine-adamantane and pyridoxine-cyclooctane dipharmacophore molecules were synthesized based on reactions of three different cycloalkylamines with the corresponding electrophilic derivatives of pyridoxine aldehydes, chlorides and acetates. Reaction of cycloalkylamines with pyridoxine derivatives, in which meta-hydroxyl and ortho-hydroxymethyl groups are protected by acetyl groups, represents a useful alternative to reductive amination of aldehydes and nucleophilic substitution of alkyl halides. According to a tentative mechanism, it proceeds via paraand ortho-pyridinone methides which readily react with nucleophiles. None of the synthesized dipharmacophore compounds showed activity against M. tuberculosis H37Rv strain. At the same time, three compounds demonstrated some antiviral activity against H3N2 (A/Aichi/2/68) influenza virus (EC50 52-88 µg/mL) that was comparable to the activity of Amantadine, though lower than the activity of Rimantadine. The results of this work can be useful in the design of physiologically active derivatives of pyridoxine and adamantane.

Conclusion:

The results of this work can be useful in the design of physiologically active derivatives of pyridoxine and adamantane.

ASR352, A potent anticancer agent: Synthesis, preliminary SAR, and biological activities against colorectal cancer bulk, 5-fluorouracil/oxaliplatin resistant and stem cells

Despite new agent development and short-term benefits in patients with colorectal cancer (CRC), metastatic CRC cure rates have not improved due to high rates of 5-fluorouracil (5-FU)/leucovorin/oxaliplatin (FOLFOX)-resistance and a clinical therapeutic plateau. At the same time, this treatment regime leads to significant toxicity, cost, and patient inconvenience. Drug-resistance is linked to CRC stem cells, which are associated with the epidermal-to-mesenchymal transition (EMT) pathway. Thus, to optimally treat CRC, a therapy that can target the cell survival and EMT pathways in both CRC bulk and stem cell populations is critical. We recently identified a novel small molecule NSC30049 (7a) that is effective alone, and in combination potentiates 5-FU-mediated growth inhibition of CRC bulk, FOLFOX-resistant, and CRC stem cells both in vitro and in vivo models. In the present study, we report the synthesis and anti-CRC evaluation of several stable and effective 7a analogs. ASR352 (7b) was identified as one of the equipotent 7a analogs that inhibited the growth of CRC bulk cells, sensitized FOLFOX-resistant cells, and reduced the sphere formation capacity of CRC stem cells. It appears that the complex mechanism of cytotoxicity for 7b includes abrogation of 5-FU-induced the S phase, reduction of the phosphorylation of Chk1 at S317P, S345P and S296P, increased γH2AX staining, activation of caspase 3/PARP1 cleavage, and enhancement of Bax/Bcl2 ratio. Further 7b-mediated reduced phosphorylation of Chk1 was an indirect effect, since it did not inhibit Chk1 activity in an in vitro kinase assay. Our findings suggest that 7b as a single agent, or in combination with 5-FU can be developed as a therapeutic agent in CRC bulk, FOLFOX-resistant, and CRC stem cell populations for unmanageable metastatic CRC conditions.

Synthesis of 2-Azaadamantan-6-one: A Missing Isomer

2-Azaadamantan-6-one and its Boc and ethylene ketal derivatives were synthesized from 9-oxo endo-bicyclo[3.3.1]non-6-ene-3-carboxylic acid. Similarly, the Cbz, Boc, and ethylene ketal derivatives of 2-azaadamantan-4-one were synthesized from endo-bicyclo[3.3.1]non-6-ene-3-carboxylic acid. Key steps were Curtius rearrangements to form benzyl carbamates, followed by spontaneous intramolecular attack of the carbamate nitrogen on transient bromonium ion or epoxide intermediates to effect ring closure to azaadamantane intermediates. The reaction sequence leading to 2-azaadamantan-6-one is consistent with the formation of a transient tetracyclic keto aziridine intermediate.

Highly potent activity of isopulegol-derived substituted octahydro-2H-chromen-4-ols against influenza A and B viruses

A set of (-)-isopulegol derived octahydro-2H-chromen-4-ols was synthesized and evaluated in vitro for antiviral activity against panel of reference influenza virus strains differing in subtype, origin (human or avian) and drug resistance. Compound (4R)-11a produced via one-pot synthesis by interaction between (-)-isopulegol and acetone was found to exhibit an outstanding activity against a number of H1N1 and H2N2 influenza virus strains with selectivity index more than 1500. (4R)-11a was shown to be most potent at early stages of viral cycle. Good correlation between anti-viral activity and calculated binding energy to hemagglutinin TBHQ active site was demonstrated.