Synthesis and antitubercular activity of amino alcohol fused spirochromone conjugates

Construction of 1,6-anhydro-functionalized carbohydrate-fused spiro-chromanones via intramolecular domino/spirocyclization

The synthetic protocol for the first synthesis of carbohydrate-fused spiro-chromanones via intramolecular domino reaction between o-hydroxyacetophenones and dihydrolevoglucosenone (DHL) is described. The reactions proceed via the formation of an acetophenone (APh) enamine intermediate when performed in the presence of pyrrolidine in ethanol. The formation of a new carbon-carbon bond between nucleophilic carbon of the enamine of APh and C-2 of DHL is followed by cyclization, producing a new six-membered ring, as the result of an intramolecular domino process. Several substituted o-hydroxyacetophenones were reacted. The structure of products was determined using 1H and 13C NMR, GC-MS and X-ray crystallography. The yields are good to excellent (62-92 %), and the products are crystalline and easy to isolate. So far, the synthesized compounds were tested only for their antifungal properties. The results were disappointing.

Spirocyclic compounds: potential drug leads in the fight against Mycobacterium tuberculosis

TB drug discovery needs scientists' attention since drug resistance in TB, including extensively drug-resistant TB (XDR-TB) and multidrug-resistant TB (MDR-TB), is a major healthcare concern. Since millions of fatalities from tuberculosis are recorded each year, there is an urgent need to discover new anti-tubercular medications that will either eradicate or control the disease. Spiro compounds have garnered a lot of attention in medicinal chemistry these days because of various biological activities mainly because of their adaptability and structural resemblance to significant pharmacophores. This article overviews the synthesis and activity of spirocyclic compounds as anti-tubercular agents. Both synthesized and naturally occurring spiro chemicals exhibit antitubercular properties. The promising antitubercular potential shown by some of the spirocyclic compounds has attracted scientists to explore them further to develop molecules with improved pharmacodynamic and pharmacokinetic properties and new mechanisms of action with enhanced safety and efficacy in tuberculosis. The current review covers the exploration of spiro compounds from the year 2004 to 2024 for the combat of Tuberculosis. This review gives the comprehensive advancements in this scaffold which would help the logical design of powerful, less toxic, and more effective spirocyclic anti-TB medicinal molecules.

Design, Synthesis and Biological Evaluation of Novel Spiro-[chroman-2,4'-piperidin]-4-one Analogues as Anti-Tubercular Agents

A series of novel spiro-[chromane-2,4'-piperidine]-4(3 H )-one derivatives were designed, synthesized and structures were confirmed by analytical methods viz., 1 H NMR, 13 C NMR and Mass spectrometry. Synthesized derivatives were evaluated for their anti-mycobacterial activity against Mycobacterium tuberculosis ( Mtb ) H37Ra strain. Among all the evaluated compounds, PS08 exhibited significant inhibition with MIC value of 3.72 μM while MIC values of the remaining compounds ranged from 7.68 to 230.42 μM in comparison to the standard drug INH (MIC 0.09 μM). The two most active compounds however showed acute cytotoxicity towards the human MRC-5 lung fibroblast cell line. The in-silico ADMET profiles of the titled compounds were predicted and found within the prescribed limits of the Lipinski and Jorgenson rules. Molecular docking study of the significantly active compound ( PS08 ) was also carried out after performing validation in order to understand the putative binding position of the test ligand at the active site of selected target protein Mtb tyrosine phosphatase (PtpB).

Chromanone-A Prerogative Therapeutic Scaffold: An Overview

Chromanone or Chroman-4-one is the most important and interesting heterobicyclic compound and acts as a building block in medicinal chemistry for isolation, designing and synthesis of novel lead compounds. Structurally, absence of a double bond in chromanone between C-2 and C-3 shows a minor difference from chromone but exhibits significant variations in biological activities. In the present review, various studies published on synthesis, pharmacological evaluation on chroman-4-one analogues are addressed to signify the importance of chromanone as a versatile scaffold exhibiting a wide range of pharmacological activities. But, due to poor yield in the case of chemical synthesis and expensive isolation procedure from natural compounds, more studies are required to provide the most effective and cost-effective methods to synthesize novel chromanone analogs to give leads to chemistry community. Considering the versatility of chromanone, this review is designed to impart comprehensive, critical and authoritative information about chromanone template in drug designing and development.

Recent advances in transition metal-free annulation toward heterocycle diversity based on the C-N bond cleavage of enaminone platform

The enaminones and analogous stable enamines are well known as platform building blocks in organic synthesis for construction of heterocyclic compounds, especially N-heterocycles. To date, especially enaminones have been successfully...

Chromone a Privileged Scaffold in Drug Discovery: Developments on the Synthesis and Bioactivity

Chromones are the class of secondary metabolites broadly occurred in the plant kingdom in a noticeable quantity. This rigid bicyclic system has been categorized "as privileged scaffolds in compounds" in medicinal chemistry. The wide biological responses made them an important moiety in a drug discovery program. This review provides updates on the various methods of synthesis of chromones and biological applications in medicinal chemistry. Various synthetic strategies for the construction of chromones include readily available phenols, salicylic acid and its derivatives, ynones, chalcones, enaminones, chalcones and 2-hydroxyarylalkylketones as starting materials. Synthesis of chromones by using metal, metal free, nanomaterials and different catalysts are included. Details of diverse biological activities such as anti-cancer agents, antimicrobial agents, anti-viral property, anti-inflammatory agents, antioxidants, Monoamine Oxidase-B (MAO-B) Inhibitors, anti-Alzheimer's agents, anti-diabetic agent, antihistaminic potential, antiplatelet agents of chromone derivatives are diecussed.

Rigid 3D-spiro chromanone as a crux for efficient antimicrobial agents: synthesis, biological and computational evaluation

The development of new and effective antimicrobial agents with novel chemical skeletons and working mechanisms is highly desirable due to the increased number of resistant microbes. Different new compounds based upon a 3D-spiro chromanone scaffold such as Mannich bases 2 and 3 in addition to azo dye 4 were synthesized. Besides, the condensation reactions of the hydrazide-spiro chromanone 8 with different ketonic reagents led to the synthesis of pyrazoles (9 & 10) and anils (11 & 13). Moreover, the methoxyl substituted spiro chromanone 14 was condensed with different hydrazines and hydrazides to give the corresponding hydrazones 15-18 in up to 85% yields. The condensation of the hydrazone 18 with salicylaldehyde yielded coumarinyl spiro chromanone 19 in an excellent yield, whereas its reaction with benzaldehyde followed by hydrazine afforded aminopyrazole derivative 21 in 82% yield. The antimicrobial evaluation suggested that hydrazide 8 has a substantial activity against different microbes (S. aureus: D = 22 mm, MIC = 1.64 μM; E. coli: D = 19 mm, MIC = 1.64 μM; C. albicans: D = 20 mm, MIC = 6.57 μM). Moreover, promising antimicrobial activities were observed for azo dye 4 (D = 13-19 mm, MIC = 5.95-11.89 μM), hydrazone 17 (D = 17-23 mm, MIC = 1.88-3.75 μM), and aminopyrazole 21 (D = 14-19 mm, MIC = 2.24-8.98 μM). The molecular docking revealed that compounds 4, 8, 17, and 21 had good to high binding affinities with different microbial targets such as penicillin-binding proteins (-7.4 to -9.9 kcal), DNA gyrase (-7.8 to -9.0 kcal), lanosterol 14-alpha demethylase (-8.2 to -11.2 kcal), and exo-beta-1,3-glucanase (-8.2 to -11.9 kcal). The QSAR analysis ascertained a good correlation between the antimicrobial activity of 3D-spiro chromanone derivatives and their structural and/or physicochemical parameters.

Synthesis of 8',11'-dihydrospiro[cyclohexane-1,2'-oxepino[2,3-h] chromen]-4'(3'H)-ones with ring closing metathesis as a key step

A series of novel hybrid molecular entities incorporating various spiro chromanone scaffolds onto the benzannulated oxepine core moiety were synthesised using allylation, Claisen rearrangement, Kabbe condensation and Ring Closing Metathesis (RCM) as a key step. During the synthesis we found that the nitrogen functionality in the substrate influences significantly the catalyst load due to electronic effects. Several iterations have been carried out to achieve complete conversion to products 6a-6e.

New Chromane-Based Derivatives as Inhibitors of Mycobacterium tuberculosis Salicylate Synthase (MbtI): Preliminary Biological Evaluation and Molecular Modeling Studies

Tuberculosis is the leading cause of death from a single infectious agent worldwide; therefore, the need for new antitubercular drugs is desperate. The recently validated target salicylate synthase MbtI is the first enzyme involved in the biosynthesis of mycobactins, compounds able to chelate iron, an essential cofactor for the survival of Mycobacterium tuberculosis in the host. Here, we report on the synthesis and biological evaluation of chromane-based compounds as new potential inhibitors of MbtI. Our approach successfully allowed the identification of a novel lead compound (1), endowed with a promising activity against this enzyme (IC₅₀ = 55 μM). Molecular modeling studies were performed in order to evaluate the binding mode of 1 and rationalize the preliminary structure-activity relationships, thus providing crucial information to carry out further optimization studies.

Identification of potent chromone embedded [1,2,3]-triazoles as novel anti-tubercular agents

A series of 20 novel chromone embedded [1,2,3]-triazoles derivatives were synthesized via an easy and convenient synthetic procedure starting from 2-hydroxy acetophenone. The in vitro anti-mycobacterial evaluation studies carried out in this work reveal that seven compounds exhibit significant inhibition against Mycobacterium tuberculosis H37Rv strain with MIC in the range of 1.56-12.5 µg ml^-1. Noticeably, compound 6s was the most potent compound in vitro with a MIC value of 1.56 µg ml^-1. Molecular docking and chemoinformatics studies revealed that compound 6s displayed drug-like properties against the enoyl-acyl carrier protein reductase of M. tuberculosis further establishing its potential as a potent inhibitor.

Transition metal free regio-selective C–H hydroxylation of chromanones towards the synthesis of hydroxyl-chromanones using PhI(OAc)2 as the oxidant

Herein, we report a highly efficient PhI(OAc)₂ mediated regioselective, direct C–H hydroxylation of chromanones.

Bis-spirochromanones as potent inhibitors of Mycobacterium tuberculosis: synthesis and biological evaluation

On the basis of reported antimycobacterial property of chroman-4-one pharmacophore, a series of chemically modified bis-spirochromanones were synthesized starting from 2-hydroxyacetophenone and 1,4-dioxaspiro[4.5] decan-8-one using a Kabbe condensation approach. The synthesized bis-spirochromanones were established based on their spectral data and X-ray crystal structure of 6e. All synthesized compounds were evaluated against Mycobacterium tuberculosis H37Rv (ATCC 27294) strain, finding that some products exhibited good antimycobacterial activity with minimum inhibitory concentration as low as [Formula: see text]. Docking studies were carried out to identify the binding interactions of compounds II, 6a and 6n with FtsZ. Compounds exhibiting good in vitro potency in the MTB MIC assay were further evaluated for toxicity using the HEK cell line.

Ring-locking strategy facilitating determination of absolute optical purity of 2-amino-1-butanol by reverse-phase high-performance liquid chromatography

A concise and efficient reverse-phase high-performance liquid chromatography (RPLC) method has been established for absolute optical purity assay of 2-amino-1-butanol, which is an important synthetic intermediate of various drugs.

Synthesis, in vitro anticancer and antimycobacterial evaluation of new 5-(2,5-dimethoxyphenyl)-1,3,4-thiadiazole-2-amino derivatives

A series of 2,5-disubstituted-1,3,4-thiadiazole derivatives 5a-5l, 7a-7e and 9 have been synthesised and screened for in vitro antimycobacterial activity against Mycobacterium smegmatis MC-155. In addition these compounds have also been screened for cytotoxic activity against cancer cell lines HT-29, MDA-MB-231 by MTT colorimetric assay. The compounds are well characterized by spectral analysis viz. (1)H NMR, (13)C NMR, FT-IR, mass and HRMS. Screening results indicate that compounds 5g, 7a possess good antitubercular activity with MIC value 65.74 and 40.86, respectively, compounds 5g, 7a, 7b, 7d, 7e and 9 displayed promising cytotoxic activity against the cell lines tested. 5g and 7a stand out to be potent antimycobacterial and anticancer agents among the tested series. Further the title compounds were also tested on human normal cells HEK293T and are found to be safer with lesser cytotoxicity. It is interesting to observe that compound 5g has come out to be safer, potent anticancer and antimycobacterial agent.

Recent advances of chroman-4-one derivatives: synthetic approaches and bioactivities

Chroman-4-one scaffold is a privileged structure in heterocyclic chemistry and drug discovery. Also, chroman-4-ones are important intermediates and interesting building blocks in organic synthesis and drug design. The structural diversity found in the chroman-4-one family led to their division into several categories including benzylidene-4-chromanones, flavanones (2-phenyl-4-chromanones), isoflavanones (3-phenyl-4-chromanones), spirochromanones, and C-4 modified chroman-4-ones such as hydrazones and oxime derivatives. This review addresses the most significant synthetic methods reported on 4-chromanone-derived compounds and consequently emphasizes on the biological relevance of such compounds.

Spirochromone-chalcone conjugates as antitubercular agents: synthesis, bio evaluation and molecular modeling studies

We report new spiro chromone scaffold derived molecules possessing in vitro anti-tubercular activities. QSAR based molecular modeling studies correlated the bioactivities with the frontier molecular orbital energies.

Synthesis of novel dispiropyrrolothiazoles by three-component 1,3-dipolar cycloaddition and evaluation of their antimycobacterial activity

A series of dispiropyrrolothiazoles derivatives has been synthesized screenedin vitroagainstMycobacterium tuberculosisH37Rv. The observed regio- and stereoselectivity of the cycloaddition reaction has been rationalized by DFT calculations.