Special Issue "Synthesis of Flavonoids or Other Nature-Inspired Small Molecules"

A special issue of Molbank (ISSN 1422-8599). This special issue belongs to the section "Natural Products".

Deadline for manuscript submissions: closed (1 February 2022) | Viewed by 14359

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Special Issue Editor

Dr. Giovanni Ribaudo
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Guest Editor
Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123 Brescia, Italy
Interests: medicinal chemistry; organic synthesis; analytical chemistry; mass spectrometry; NMR; natural products; molecular modeling
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Every organic chemist should agree that, as stated by Nobel Laureate Frances H. Arnold, “by far, nature is the best chemist of all time”. Natural compounds are characterized by a unique variety of chemical structures, functional groups, and stereochemical properties. Moreover, from the medicinal chemistry point of view, several naturally occurring small molecules are endowed with valuable biological activities and have inspired the design and development of drugs.

Flavonoids represent an outstanding example among natural compounds. These molecules are polyphenols produced by plants and fungi, constituted by two phenyls and a heterocyclic ring, disposed differently according to the sub-category. Flavonoids and semi-synthetic derivatives have been extensively studied in light of their wide bioactivity spectrum: antioxidant, antiproliferative, antibacterial and anti-inflammatory. In addition, several other classes of natural or nature-inspired molecules, such as alkaloids and terpenoids, are particularly attractive from a chemical or biological perspective.

This Special Issue aims at collating original contributions describing the synthesis of natural compounds and semi-synthetic derivatives of natural molecules. Articles should contain original and efficient synthetic approaches or significant process innovations in the preparation of natural and semi-synthetic compounds, with a particular focus on biologically relevant molecules. Moreover, research articles reporting significant results concerning extraction procedures, structural elucidation and structural characterization of natural compounds and derivatives involving the use of advanced analytical techniques (chromatography, 1D and 2D NMR, mass spectrometry, IR and UV spectroscopy) are particularly welcome.

Dr. Giovanni Ribaudo
Guest Editor

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Keywords

  • flavonoids
  • alkaloids
  • natural compounds
  • semi-synthetic compounds
  • heterocycles
  • organic chemistry
  • stereochemistry
  • structural elucidation
  • analytical chemistry

Published Papers (11 papers)

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Editorial

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Editorial
Synthesis of Flavonoids or Other Nature-Inspired Small Molecules
Molbank 2022, 2022(1), M1313; https://doi.org/10.3390/M1313 - 10 Jan 2022
Viewed by 660
Abstract
Natural compounds are endowed with an intriguing variety of scaffolds, functional groups and stereochemical properties [...] Full article
(This article belongs to the Special Issue Synthesis of Flavonoids or Other Nature-Inspired Small Molecules)

Research

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Communication
New Derivatives of Lupeol and Their Biological Activity
Molbank 2021, 2021(4), M1306; https://doi.org/10.3390/M1306 - 10 Dec 2021
Cited by 1 | Viewed by 1040
Abstract
The natural product lupeol (1) was isolated from Bombax ceiba leaves, which were used as starting material in the semisynthetic approach. Three new derivatives (2a, 2b, and 3) were synthesized using oxidation and aldolization. Their chemical structures [...] Read more.
The natural product lupeol (1) was isolated from Bombax ceiba leaves, which were used as starting material in the semisynthetic approach. Three new derivatives (2a, 2b, and 3) were synthesized using oxidation and aldolization. Their chemical structures were elucidated by spectroscopic analyses (HRESIMS and NMR). Compounds 3 showed significant α-glucosidase inhibition with an IC50 value of 202 µM, whereas 2a and 2b were inactive. Full article
(This article belongs to the Special Issue Synthesis of Flavonoids or Other Nature-Inspired Small Molecules)
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Short Note
2-Oxo-2H-chromen-7-yl 4-chlorobenzoate
Molbank 2021, 2021(3), M1279; https://doi.org/10.3390/M1279 - 14 Sep 2021
Cited by 4 | Viewed by 1010
Abstract
We describe the synthesis of 2-oxo-2H-chromen-7-yl 4-chlorobenzoate 3 in 88% yield by the O-acylation reaction of 7-hydroxy-2H-chromen-2-one 1 with 4-chlorobenzoyl chloride 2 in dichloromethane using a slight excess of triethylamine at 20 °C for 1 h. The ester [...] Read more.
We describe the synthesis of 2-oxo-2H-chromen-7-yl 4-chlorobenzoate 3 in 88% yield by the O-acylation reaction of 7-hydroxy-2H-chromen-2-one 1 with 4-chlorobenzoyl chloride 2 in dichloromethane using a slight excess of triethylamine at 20 °C for 1 h. The ester 3 was completely characterized by mass spectrometry, IR, UV–Vis, 1D, and 2D NMR spectroscopy. Full article
(This article belongs to the Special Issue Synthesis of Flavonoids or Other Nature-Inspired Small Molecules)
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Article
2-Chloro-4,6-bis{(E)-3-methoxy-4-[(4-methoxybenzyl)oxy]styryl}pyrimidine: Synthesis, Spectroscopic and Computational Evaluation
Molbank 2021, 2021(3), M1276; https://doi.org/10.3390/M1276 - 07 Sep 2021
Cited by 1 | Viewed by 898
Abstract
A novel curcumin analog namely 2-chloro-4,6-bis{(E)-3-methoxy-4-[(4-methoxybenzyl)oxy]-styryl}pyrimidine (compound 7) was synthesized by three-step reaction. The condensation reaction of protected vanillin with 2-chloro-4,6-dimethylpyrimidine (6) was the most efficient step, resulting in a total yield of 72%. The characterization [...] Read more.
A novel curcumin analog namely 2-chloro-4,6-bis{(E)-3-methoxy-4-[(4-methoxybenzyl)oxy]-styryl}pyrimidine (compound 7) was synthesized by three-step reaction. The condensation reaction of protected vanillin with 2-chloro-4,6-dimethylpyrimidine (6) was the most efficient step, resulting in a total yield of 72%. The characterization of compound 7 was performed by 1H and 13C nuclear magnetic resonance (NMR), as well as high-resolution mass spectrometry. The experimental spectrometric data were compared with the theoretical spectra obtained by the density functional theory (DFT) method, showing a perfect match between them. UV-visible spectroscopy and steady-state fluorescence emission studies were performed for compound 7 in solvents of different polarities and the results were correlated with DFT calculations. Compound 7 showed a solvatochromism effect presenting higher molar extinction coefficient (log ε = 4.57) and fluorescence quantum yield (ϕ = 0.38) in toluene than in acetonitrile or methanol. The simulation of both frontier molecular orbitals (FMOs) and molecular electrostatic potential (MEP) suggested that the experimental spectra profile in toluene was not interfered by a possible charge transfer. These results are an indication of a low probability of compound 7 in reacting with unsaturated phospholipids in future applications as a fluorescent dye in biological systems. Full article
(This article belongs to the Special Issue Synthesis of Flavonoids or Other Nature-Inspired Small Molecules)
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Communication
Bioactive Antidiabetic Flavonoids from the Stem Bark of Cordia dichotoma Forst.: Identification, Docking and ADMET Studies
Molbank 2021, 2021(2), M1234; https://doi.org/10.3390/M1234 - 11 Jun 2021
Cited by 12 | Viewed by 1436
Abstract
Cordia dichotoma Forst. (F. Boraginaceae) has been traditionally used for the management of a variety of human ailments. In our earlier work, the antidiabetic activity of methanolic bark extract of C. dichotoma (MECD) has been reported. In this paper, two flavonoid molecules were [...] Read more.
Cordia dichotoma Forst. (F. Boraginaceae) has been traditionally used for the management of a variety of human ailments. In our earlier work, the antidiabetic activity of methanolic bark extract of C. dichotoma (MECD) has been reported. In this paper, two flavonoid molecules were isolated (by column chromatography) and identified (by IR, NMR and mass spectroscopy/spectrometry) from the MECD with an aim to investigate their antidiabetic effectiveness. Molecular docking and ADMET studies were carried out using AutoDock Vina software and Swiss ADME online tool, respectively. The isolated flavonoids were identified as 3,5,7,3′,4′-tetrahydroxy-4-methoxyflavone-3-O-l-rhamnopyranoside and 5,7,3′-trihydroxy-4-methoxyflavone-7-O-l-rhamnopyranoside (quercitrin). Docking and ADMET studies revealed the promising binding affinity of flavonoid molecules for human lysosomal α-glucosidase and human pancreatic α-amylase with acceptable ADMET properties. Based on computational studies, our study reports the antidiabetic potential of the isolated flavonoids with predictive pharmacokinetics profile. Full article
(This article belongs to the Special Issue Synthesis of Flavonoids or Other Nature-Inspired Small Molecules)
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Short Note
Kokosanolide D: A New Tetranortriterpenoid from Fruit Peels of Lansium domesticum Corr. cv Kokossan
Molbank 2021, 2021(2), M1232; https://doi.org/10.3390/M1232 - 10 Jun 2021
Cited by 3 | Viewed by 1155
Abstract
A novel tetranortriterpenoid named kokosanolide D has been isolated from fruit peels of Lansium domesticum. The structure of kokosanolide D was elucidated primarily on the basis of spectroscopic data including infrared, 1D and 2D-NMR, as well as high resolution mass spectroscopy analysis [...] Read more.
A novel tetranortriterpenoid named kokosanolide D has been isolated from fruit peels of Lansium domesticum. The structure of kokosanolide D was elucidated primarily on the basis of spectroscopic data including infrared, 1D and 2D-NMR, as well as high resolution mass spectroscopy analysis and comparison with related compounds previously reported. Full article
(This article belongs to the Special Issue Synthesis of Flavonoids or Other Nature-Inspired Small Molecules)
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Short Note
N-[7-Chloro-4-[4-(phenoxymethyl)-1H-1,2,3-triazol-1-yl]quinoline]-acetamide
Molbank 2021, 2021(2), M1213; https://doi.org/10.3390/M1213 - 20 May 2021
Cited by 4 | Viewed by 1108
Abstract
The 1,2,3-triazole is a well-known biologically active pharmacophore constructed by the copper-catalyzed azide–alkyne cycloaddition. We herein reported the synthesis of 4-amino-7-chloro-based [1,2,3]-triazole hybrids via Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition of 4-azido-7-chloroquinoline with an alkyne derivative of acetaminophen. The compound was fully characterized by Fourier-transform [...] Read more.
The 1,2,3-triazole is a well-known biologically active pharmacophore constructed by the copper-catalyzed azide–alkyne cycloaddition. We herein reported the synthesis of 4-amino-7-chloro-based [1,2,3]-triazole hybrids via Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition of 4-azido-7-chloroquinoline with an alkyne derivative of acetaminophen. The compound was fully characterized by Fourier-transform infrared (FTIR), proton nuclear magnetic resonance (1H-NMR), carbon-13 nuclear magnetic resonance (13C-NMR), heteronuclear single quantum coherence (HSQC), ultraviolet (UV) and high-resolution mass spectroscopies (HRMS). This compound was screened in vitro with different normal and cancer cell lines. The drug likeness of the compound was also investigated by predicting its pharmacokinetic properties. Full article
(This article belongs to the Special Issue Synthesis of Flavonoids or Other Nature-Inspired Small Molecules)
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Short Note
2-Propyl-N′-[1,7,7-trimethylbicyclo[2.2.1]hept-2-ylidene]pentanehydrazide
Molbank 2020, 2020(4), M1164; https://doi.org/10.3390/M1164 - 26 Oct 2020
Cited by 1 | Viewed by 1114
Abstract
2-Propyl-N′-[1,7,7-trimethylbicyclo[2.2.1]hept-2-ylidene]pentanehydrazide was obtained in 80% yield via the Einhorn variation of the Schotten–Baumann method by (+)-camphor hydrazide condensation with valproic acid (VPA) chloride. The structure of the titled compound was verified by Raman, FTIR, 1H-NMR, and 13C-NMR spectral analysis [...] Read more.
2-Propyl-N′-[1,7,7-trimethylbicyclo[2.2.1]hept-2-ylidene]pentanehydrazide was obtained in 80% yield via the Einhorn variation of the Schotten–Baumann method by (+)-camphor hydrazide condensation with valproic acid (VPA) chloride. The structure of the titled compound was verified by Raman, FTIR, 1H-NMR, and 13C-NMR spectral analysis along with FAB-mass spectrometry. Thermal properties of synthesized derivative were elucidated by DSC and its purity by HPLC. The compound was successfully tested as a potential anticonvulsant agent based on models of chemically- and electrically-induced seizures. Full article
(This article belongs to the Special Issue Synthesis of Flavonoids or Other Nature-Inspired Small Molecules)
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Short Note
3-Hydroxy-8,14-secogammacera-7,14-dien-21-one: A New Onoceranoid Triterpenes from Lansium domesticum Corr. cv kokossan
Molbank 2020, 2020(4), M1157; https://doi.org/10.3390/M1157 - 30 Sep 2020
Cited by 5 | Viewed by 1512
Abstract
A new onoceranoid triterpenes, namely 3-hydroxy-8,14-secogammacera-7,14-dien-21-one (1), has been isolated from the fruit peels of Lansium domesticum Corr. cv kokossan. The structure of 1 was determined on the basis of spectroscopic data including infrared, 1D and 2D-NMR, as well as [...] Read more.
A new onoceranoid triterpenes, namely 3-hydroxy-8,14-secogammacera-7,14-dien-21-one (1), has been isolated from the fruit peels of Lansium domesticum Corr. cv kokossan. The structure of 1 was determined on the basis of spectroscopic data including infrared, 1D and 2D-NMR, as well as high resolution mass spectroscopy analysis. Compound 1 showed a weak activity against MCF-7 breast cancer cell lines. Full article
(This article belongs to the Special Issue Synthesis of Flavonoids or Other Nature-Inspired Small Molecules)
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Short Note
5,5′-Oxybis(1,3,7-trihydroxy-9H-xanthen-9-one): A New Xanthone from the Stem Bark of Garcinia porrecta (Clusiaceae)
Molbank 2020, 2020(3), M1153; https://doi.org/10.3390/M1153 - 12 Aug 2020
Cited by 1 | Viewed by 1259
Abstract
A new polyoxygenated dimer-type xanthone, namely 5,5′-oxybis(1,3,7-trihydroxy-9H-xanthen-9-one (1), has been isolated from the stem bark of Garcinia porrecta. The structure of 1 was determined based on spectroscopic data, including 1D and 2D-NMR as well as high resolution mass spectroscopy analysis. Full article
(This article belongs to the Special Issue Synthesis of Flavonoids or Other Nature-Inspired Small Molecules)
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Short Note
2-(3,4-Dihydroxyphenyl)-4-(2-(4-nitrophenyl)hydrazono)-4H-chromene-3,5,7-triol
Molbank 2020, 2020(3), M1144; https://doi.org/10.3390/M1144 - 29 Jun 2020
Cited by 6 | Viewed by 1535
Abstract
On the basis of the knowledge from traditional herbal and folk medicine, flavonoids are among the most studied chemical classes of natural compounds for their potential activity as phosphodiesterase 5 (PDE5) inhibitors. We here describe the preparation of a semi-synthetic hydrazone derivative of [...] Read more.
On the basis of the knowledge from traditional herbal and folk medicine, flavonoids are among the most studied chemical classes of natural compounds for their potential activity as phosphodiesterase 5 (PDE5) inhibitors. We here describe the preparation of a semi-synthetic hydrazone derivative of quercetin, 2-(3,4-dihydroxyphenyl)-4-(2-(4-nitrophenyl)hydrazono)-4H-chromene-3,5,7-triol, that was obtained via a single-step modification of the natural compound. The product was characterized by NMR, mass spectrometry and HPLC. Preliminary molecular modeling studies suggest that this compound could efficiently interact with PDE5. Full article
(This article belongs to the Special Issue Synthesis of Flavonoids or Other Nature-Inspired Small Molecules)
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