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4 H-Chromene and 1,4-naphthoquinone systems are generally considered to be medicinally privileged scaffolds. We have designed novel conjugates that incorporated both these scaffolds, as such conjugates exhibit unique biological properties reflecting those due to individual units and collective presence. In this work, we have achieved facile, efficient, and high yielding synthesis of 19 such conjugates from readily available 2-alkylamino-4-methylsulfanyl-3-nitro-4 H-chromenes and 2-hydroxynaphthalene-1,4-dione. Highly polar nitroketene- O, N-acetal unit present in the conjugates is designed to prevent crossing blood brain barrier. We have conducted structure activity relationship (SAR) studies based on initial antimicrobial screening of a set of ten conjugates against three Gram positive bacteria [ Bacillus Subtilis, Staphylococcus aureus (MSSA), Staphylococcus aureus (MRSA)], one Gram negative bacteria ( Escherichia coli), and two fungi ( Aspergillus niger, Candida albicans). The SAR studies revealed that the conjugates with halogens at C(6) and C(8) positions of the 4 H-chromene ring having C(2)NMe group display impressive activity, almost equal to that of standard drugs. None of the conjugates, however, showed antimalarial activity, although they possess 2-hydroxy-1,4-naphthoquinone unit. [ABSTRACT FROM AUTHOR]

An efficient method was developed for the diastereoselective synthesis of novel fused dihydro-1H-furo[2,3-c]pyrazole by a one-pot, four-component reaction ofβ-keto ester, hydrazine, aromatic aldehyde, and pyridinium ylide in the presence of triethylamine under microwave irradiation in solvent-free conditions in good yields. The merits of this cascade Knoevenagel condensation/Michael addition/cyclization sequence include its high atom economy, good yields, and efficiency of producing three new bonds (two C–C and one C–O) and two stereocenters in a single operation. [ABSTRACT FROM PUBLISHER]

An efficient method was developed for the synthesis of dihydrofuran substituted coumarin from a one-pot, four-component reaction of 2-hydroxy aromatic aldehydes, 6-methyl, 4-hydroxy pyranone, aromatic aldehyde, and pyridinium ylide in the presence of tri-ethylamine under microwave irradiation. The reaction proceeds under solvent-free conditions to afford C3-dihydrofuran substituted coumarin in a diastereoselective manner in good yields (71–89%). [ABSTRACT FROM PUBLISHER]

The reaction of N-methyl-4-(methylthio)-3-nitro-4 H-chromen-2-amine and its derivatives with 4-hydroxy-6-methyl-2 H-pyran-2-one in EtOH reflux for 5 min furnish 4-hydroxy-6-methyl-3-(2-(methylamino)-3-nitro-4 H-chromen-4-yl)-2 H-pyran-2-ones in quantitative yield. By extending EtOH reflux for 2 h, the 4 H-chromene 4-hydroxy-2-pyranone conjugates get converted into acetoacetyl coumarins. Similar reaction of N-methyl-4-(methylthio)-3-nitro-4 H-chromen-2-amine and its derivatives with 4-hydroxycoumarin in EtOH reflux furnish 4-hydroxy-2′-(methylamino)-3′-nitro-2 H,4′ H-3,4′-bichromen-2-ones. In contrast to earlier system, prolonging reflux in EtOH or in n-PrOH reflux the product gets transformed into trans-ethyl 3-(2-hydroxyaryl)-4-oxo-3,4-dihydro-2 H-furo[3,2-c]chromene-2-carboxylates. Thus, facile synthesis and characterization of 4 H-chromene 4-hydroxy-2-pyrone, 4 H-chromene 4-hydroxycoumarin conjugates, acetoacetyl coumarins and trans2,3-disubstituted dihydrofuro[3,2- c]coumarins is described. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The article presents chemical equations for the article "One-Pot Multicomponent Diastereoselective Synthesis of Novel Dihydro-1H-furo[2,3-c]pyrazoles" by V. S. Tangeti and others published in the journal "Synthetic Communications" in 2016.

An abstract of the article "Synthesis of C3-Dihydrofuran Substituted Coumarins via Multicomponent Approach" by Venkata Swamy Tangeti and colleagues is presented.

The article presents a chemical reaction formula related to the synthesis and transformations of 4H-chromene 4-hydroxy-2H-pyran-2-one and 4H-Chromene 4-Hydroxycoumarin conjugates.

This study aimed to propose a straightforward and highly sensitive HPLC method for the evaluation of letermovir, coupled with an examination of the stress degradation nature of letermovir. Chromatographic separation analytes were attained using a Phenomenex Luna C18 column (250 mm x 4.6 mm; 5 μm id) maintained at 35 °C. The mobile phase comprises 0.1% phosphoric acid, methanol, and acetonitrile in 45:25:30 (v/v) facilitated isocratic elution at 0.8 mL/min with 234 nm wavelength. Under the proposed conditions, retention times were determined to be 9.58 min for letermovir and 11.10 min, 4.18 min, 6.30 min, and 13.26 min for impurities 1, 2, 3, and 4, respectively. The method achieved a sensitive detection limit of 0.009 with 0.05-0.2 μg/mL as the linear range for impurities. Other validation tests met acceptable criteria for letermovir and impurities. Additionally, stress degradation tests were conducted following ICH Q1A (R2) guidelines, subjecting the drug to various stress conditions. LC-MS/MS analysis identified five degradation products (DPs), of which DP 1, 4, and 5 were formed due to acid stress, whereas DP 2, 3 and 5 were formed due to peroxide, base and UV stress respectively. The possible structure of DPs was assessed by the interpretation and correlation of mass fragment data. The validation test produces satisfactory results supporting the suitability of the method for regular analysis of letermovir and its impurities. Moreover, the method is applicable for evaluating the degradation mechanism of letermovir. [ABSTRACT FROM AUTHOR]

Flavone-based o-hydroxybenzaldehydes (I), obtained by regioselective Duff reaction, are condensed with α-oxoketene dithioacetals (II) to furnish title compounds (III) as potentially bioactive and fluorescent materials. [ABSTRACT FROM AUTHOR]