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25 pages, 5564 KiB

Open AccessArticle

The Influence of the Functional Group on the Physicochemical and Biological Properties of New Phenanthro[9,10-d]-Imidazole Derivatives

by Slawomir Kula, Paweł Kalarus, Łukasz Kaźmierski, Anna Biernasiuk and Przemysław Krawczyk

Molecules 2024, 29(19), 4703; https://doi.org/10.3390/molecules29194703 - 4 Oct 2024

Viewed by 992

Abstract

The search for safe, cheap, and repeatable diagnostic methods is a fundamental research goal. Currently, great hope is placed on fluorescence imaging. However, the development of this method mainly depends on efficient fluorescent probes. Designing and obtaining new probes with potential applications in [...] Read more.

The search for safe, cheap, and repeatable diagnostic methods is a fundamental research goal. Currently, great hope is placed on fluorescence imaging. However, the development of this method mainly depends on efficient fluorescent probes. Designing and obtaining new probes with potential applications in fluorescence imaging is very difficult because compounds of this type must meet several requirements related to their properties. Therefore, this article attempted to obtain and study new phenanthro[9,10-d]-imidazole derivatives (PK1–PK3) with potential application as fluorescent probes for fluorescence imaging. The main goal of the work was to assess the effect of two functional groups (such as the formyl group (PK2) and rhodanine-3-acetic acid (PK3)) on selected physicochemical properties and possibilities of practical application of the considered compounds. The conducted studies proved that the influence of the functional group is significant, as it causes a bathochromic shift in both absorption and emission results (by the order PK1 < PK2 < PK3). Moreover, all compounds could stain live cells cultured in vitro. The staining efficiency was not affected by the cell line, thanks to which we obtained the correct staining of both mouse and human cell lines. PK3 was the most attractive of the tested compounds due to its staining potential of live cells and retention after fixation. Our results also showed some antibacterial and antifungal activity of the newly synthesized compounds (PK1–PK3). Among them, PK3 showed the highest antimicrobial effect, especially against Gram-positive bacteria. Full article

(This article belongs to the Special Issue Synthetic Studies Aimed at Heterocyclic Organic Compounds)

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15 pages, 2396 KiB

Open AccessArticle

Pushing at the Boundaries of Pterin Chemistry

by Jevy V. Correia, Siva S. M. Bandaru and Carola Schulzke

Molecules 2024, 29(19), 4587; https://doi.org/10.3390/molecules29194587 - 27 Sep 2024

Viewed by 563

Abstract

Pterins are molecules of substantial interest as they occur in nature in a number of forms with quite distinct and often indispensable roles. Chemically, the synthesis of the principle pterin scaffold is comparably simple, while the insolubility of the pterin building block renders [...] Read more.

Pterins are molecules of substantial interest as they occur in nature in a number of forms with quite distinct and often indispensable roles. Chemically, the synthesis of the principle pterin scaffold is comparably simple, while the insolubility of the pterin building block renders synthetic derivatization extremely difficult. When aiming at modeling naturally occurring pterins of extended chemical structure, this is a considerable problem. A notable set of strategies was developed in the course of the present study, which are able to overcome the lack of reactivity of the pterin backbone. These include a strategic choice regarding protection groups, uncommon chemical transformation, ball milling and combinations thereof. Some novel pterins with quite distinct substitution motifs were successfully synthesized and characterized by spectroscopic and spectrometric analyses as well as single-crystal structural analyses for three of them. Full article

(This article belongs to the Special Issue Synthetic Studies Aimed at Heterocyclic Organic Compounds)

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15 pages, 1610 KiB

Open AccessArticle

Linear and Angular Heteroannulated Pyridines Tethered 6-Hydroxy-4,7-Dimethoxybenzofuran: Synthesis and Antimicrobial Activity

by Najla A. Alshaye, Al-Shimaa Badran and Magdy A. Ibrahim

Molecules 2024, 29(18), 4496; https://doi.org/10.3390/molecules29184496 - 22 Sep 2024

Viewed by 565

Abstract

2-Chloropyridine-3-carbonitrile derivative 1 was utilized as a key precursor to build a series of linear and angular annulated pyridines linked to a 6-hydroxy-4,7-dimethoxybenzofuran moiety. Reaction of substrate 1 with various hydrazines afforded pyrazolo[3,4-b]pyridines. Treatment of substrate 1 with 1,3-N, [...] Read more.

2-Chloropyridine-3-carbonitrile derivative 1 was utilized as a key precursor to build a series of linear and angular annulated pyridines linked to a 6-hydroxy-4,7-dimethoxybenzofuran moiety. Reaction of substrate 1 with various hydrazines afforded pyrazolo[3,4-b]pyridines. Treatment of substrate 1 with 1,3-N,N-binucleophiles including 3-amino-1,2,4-triazole, 5-amino-1H-tetrazole, 3-amino-6-methyl-1,2,4-triazin-5(4H)-one and 2-aminobenzimidazole produced the novel angular pyrido[3,2-e][1,2,4]triazolo[4,3-a]pyrimidine, pyrido[3,2-e][1,2,4]tetrazolo[1,5-a]pyrimidine, pyrido[3′,2′:5,6] pyrimido[2,1-c][1,2,4]triazine and benzo[4,5]imidazo[1,2-a]pyrido[3,2-e]pyrimidine, respectively. Reaction of substrate 1 with 1,3-C,N-binucleophiles including cyanoacetamides and 1H-benzimidazol-2-ylacetonitrile furnished 1,8-naphthyridines and benzoimidazonaphthyridine. Moreover, reacting substrate 1 with 5-aminopyrazoles gave pyrazolo[3,4-b][1,8]naphthyridines. Finally, reaction of compound 1 with 6-aminouracils as cyclic enamines yielded pyrimido[4,5-b][1,8]naphthyridines. Some of the synthesized products showed noteworthy antimicrobial efficiency against all types of microbial strains. Structures of the produced compounds were established using analytical and spectroscopic tools. Full article

(This article belongs to the Special Issue Synthetic Studies Aimed at Heterocyclic Organic Compounds)

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8 pages, 1063 KiB

Open AccessArticle

Copper(I)-Catalyzed Formal [4 + 2] Cyclocondensation of ortho-Hydroxybenzyl Alcohol, Aromatic Terminal Alkynes, and Sulfonyl Azides: An Alternative Approach to 2-Sulfonyliminocoumarins

by Dost Muhammad Khan, Jiaying Lv and Ruimao Hua

Molecules 2024, 29(14), 3426; https://doi.org/10.3390/molecules29143426 - 22 Jul 2024

Viewed by 780

Abstract

In this paper, an alternative and efficient copper(I)-catalyzed synthesis of 2-sulfonyliminocoumarins is developed through a three-component reaction of ortho-hydroxybenzyl alcohol, alkynes, and p-toluenesulfonyl azide. The proposed route for access to the 2-iminocoumarin ring involves a [4 + 2] hetero-Diels-Alder reaction between [...] Read more.

In this paper, an alternative and efficient copper(I)-catalyzed synthesis of 2-sulfonyliminocoumarins is developed through a three-component reaction of ortho-hydroxybenzyl alcohol, alkynes, and p-toluenesulfonyl azide. The proposed route for access to the 2-iminocoumarin ring involves a [4 + 2] hetero-Diels-Alder reaction between ortho-quinone methide and ketenimine intermediates generated in situ. Full article

(This article belongs to the Special Issue Synthetic Studies Aimed at Heterocyclic Organic Compounds)

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21 pages, 5238 KiB

Open AccessArticle

Synthesis and Biological Properties of Fluorescent Strigolactone Mimics Derived from 1,8-Naphthalimide

by Ioana-Alexandra Bala, Alina Nicolescu, Florentina Georgescu, Florea Dumitrascu, Anton Airinei, Radu Tigoianu, Emilian Georgescu, Diana Constantinescu-Aruxandei, Florin Oancea and Calin Deleanu

Molecules 2024, 29(10), 2283; https://doi.org/10.3390/molecules29102283 - 12 May 2024

Viewed by 1204

Abstract

Strigolactones (SLs) have potential to be used in sustainable agriculture to mitigate various stresses that plants have to deal with. The natural SLs, as well as the synthetic analogs, are difficult to obtain in sufficient amounts for practical applications. At the same time, [...] Read more.

Strigolactones (SLs) have potential to be used in sustainable agriculture to mitigate various stresses that plants have to deal with. The natural SLs, as well as the synthetic analogs, are difficult to obtain in sufficient amounts for practical applications. At the same time, fluorescent SLs would be useful for the mechanistic understanding of their effects based on bio-imaging or spectroscopic techniques. In this study, new fluorescent SL mimics containing a substituted 1,8-naphthalimide ring system connected through an ether link to a bioactive furan-2-one moiety were prepared. The structural, spectroscopic, and biological activity of the new SL mimics on phytopathogens were investigated and compared with previously synthetized fluorescent SL mimics. The chemical group at the C-6 position of the naphthalimide ring influences the fluorescence parameters. All SL mimics showed effects similar to GR24 on phytopathogens, indicating their suitability for practical applications. The pattern of the biological activity depended on the fungal species, SL mimic and concentration, and hyphal order. This dependence is probably related to the specificity of each fungal receptor–SL mimic interaction, which will have to be analyzed in-depth. Based on the biological properties and spectroscopic particularities, one SL mimic could be a good candidate for microscopic and spectroscopic investigations. Full article

(This article belongs to the Special Issue Synthetic Studies Aimed at Heterocyclic Organic Compounds)

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22 pages, 2429 KiB

Open AccessArticle

Desymmetrization of Prochiral N-Pyrazolyl Maleimides via Organocatalyzed Asymmetric Michael Addition with Pyrazolones: Construction of Tri-N-Heterocyclic Scaffolds Bearing Both Central and Axial Chirality

by Jianqi Geng, Xingfu Wei, Biru He, Yuting Hao, Jingping Qu and Baomin Wang

Molecules 2023, 28(11), 4279; https://doi.org/10.3390/molecules28114279 - 23 May 2023

Cited by 2 | Viewed by 1594

Abstract

The desymmetrization of N-pyrazolyl maleimides was realized through an asymmetric Michael addition by using pyrazolones under mild conditions, leading to the formation of a tri-N-heterocyclic pyrazole–succinimide–pyrazolone assembly in high yields with excellent enantioselectivities (up to 99% yield, up to 99% [...] Read more.

The desymmetrization of N-pyrazolyl maleimides was realized through an asymmetric Michael addition by using pyrazolones under mild conditions, leading to the formation of a tri-N-heterocyclic pyrazole–succinimide–pyrazolone assembly in high yields with excellent enantioselectivities (up to 99% yield, up to 99% ee). The use of a quinine-derived thiourea catalyst was essential for achieving stereocontrol of the vicinal quaternary–tertiary stereocenters together with the C–N chiral axis. Salient features of this protocol included a broad substrate scope, atom economy, mild conditions and simple operation. Moreover, a gram-scale experiment and derivatization of the product further illustrated the practicability and potential application value of this methodology. Full article

(This article belongs to the Special Issue Synthetic Studies Aimed at Heterocyclic Organic Compounds)

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18 pages, 3667 KiB

Open AccessFeature PaperArticle

Structure and Conformational Mobility of OLED-Relevant 1,3,5-Triazine Derivatives

by Georgi M. Dobrikov, Yana Nikolova, Ivaylo Slavchev, Miroslav Dangalov, Vera Deneva, Liudmil Antonov and Nikolay G. Vassilev

Molecules 2023, 28(3), 1248; https://doi.org/10.3390/molecules28031248 - 27 Jan 2023

Cited by 1 | Viewed by 2189

Abstract

A series of OLED-relevant compounds, consisting of 1,3,5-triazine core linked to various aromatic arms by amino group, has been synthesized and characterized. The studied compounds exist in solution as a mixture of two conformers, a symmetric propeller and asymmetric conformer, in which one [...] Read more.

A series of OLED-relevant compounds, consisting of 1,3,5-triazine core linked to various aromatic arms by amino group, has been synthesized and characterized. The studied compounds exist in solution as a mixture of two conformers, a symmetric propeller and asymmetric conformer, in which one of the aromatic arms is rotated around the C-N bond. At temperatures below −40 °C, the VT NMR spectra in DMF-d7 are in a slow exchange regime, and the signals of two conformers can be elucidated. At temperatures above 100 °C, the VT NMR spectra in DMSO-d6 are in a fast exchange regime, and the averaged spectra can be measured. The ratio of symmetric and asymmetric conformers in DMF-d7 varies from 14:86 to 50:50 depending on the substituents. The rotational barriers of symmetric and asymmetric conformers in DMF-d7 were measured for all compounds and are in the interval from 11.7 to 14.7 kcal/mol. The ground-state energy landscapes of the studied compounds, obtained by DFT calculations, show good agreement with the experimental rotational barriers. The DFT calculations reveal that the observed chemical exchange occurs by the rotation around the C(1,3,5-triazine)-N bond. Although some of the compounds are potentially tautomeric, the measured absorption and emission spectra do not indicate proton transfer neither in the ground nor in the excited state. Full article

(This article belongs to the Special Issue Synthetic Studies Aimed at Heterocyclic Organic Compounds)

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Review

Jump to: Research

14 pages, 3394 KiB

Open AccessReview

Recent Advances in the Synthesis of the Marine-Derived Alkaloid Fascaplysin and Its Metabolites Homofascaplysins A–C

by Ramana Reddy Mittapalli and Harshita Kumari

Molecules 2024, 29(7), 1590; https://doi.org/10.3390/molecules29071590 - 2 Apr 2024

Viewed by 1194

Abstract

The fascaplysin and homofascaplysin class of marine natural products has a characteristic 12H-pyrido[1,2-a:3,4-b′]diindole pentacyclic structure. Fascaplysin was isolated in 1988 from the marine sponge Fascaplysinopsis bergquist sp. The analogs of fascaplysin, such as homofascaplysins A, B, and C, were discovered late in the [...] Read more.

The fascaplysin and homofascaplysin class of marine natural products has a characteristic 12H-pyrido[1,2-a:3,4-b′]diindole pentacyclic structure. Fascaplysin was isolated in 1988 from the marine sponge Fascaplysinopsis bergquist sp. The analogs of fascaplysin, such as homofascaplysins A, B, and C, were discovered late in the Fijian sponge F. reticulate, and also have potent antimicrobial activity and strong cytotoxicity against L-1210 mouse leukemia. In this review, the total synthesis of fascaplysin and its analogs, such as homofascaplysins A, B, and C, will be reviewed, which will offer useful information for medicinal chemistry researchers who are interested in the exploration of marine alkaloids. Full article

(This article belongs to the Special Issue Synthetic Studies Aimed at Heterocyclic Organic Compounds)

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44 pages, 40252 KiB

Open AccessReview

Recent Advances in Synthetic Routes to Azacycles

by Anh Thu Nguyen and Hee-Kwon Kim

Molecules 2023, 28(6), 2737; https://doi.org/10.3390/molecules28062737 - 17 Mar 2023

Cited by 5 | Viewed by 2346

Abstract

A heterocycle is an important structural scaffold of many organic compounds found in pharmaceuticals, materials, agrochemicals, and biological processes. Azacycles are one of the most common motifs of a heterocycle and have a variety of applications, including in pharmaceuticals. Therefore, azacycles have received [...] Read more.

A heterocycle is an important structural scaffold of many organic compounds found in pharmaceuticals, materials, agrochemicals, and biological processes. Azacycles are one of the most common motifs of a heterocycle and have a variety of applications, including in pharmaceuticals. Therefore, azacycles have received significant attention from scientists and a variety of methods of synthesizing azacycles have been developed because their efficient synthesis plays a vital role in the production of many useful compounds. In this review, we summarize recent approaches to preparing azacycles via different methods as well as describe plausible reaction mechanisms. Full article

(This article belongs to the Special Issue Synthetic Studies Aimed at Heterocyclic Organic Compounds)

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56 pages, 37176 KiB

Open AccessReview

Methods of Lysergic Acid Synthesis—The Key Ergot Alkaloid

by Michał K. Jastrzębski, Agnieszka A. Kaczor and Tomasz M. Wróbel

Molecules 2022, 27(21), 7322; https://doi.org/10.3390/molecules27217322 - 28 Oct 2022

Cited by 12 | Viewed by 37271

Abstract

Ergot is the spore form of the fungus Claviceps purpurea. Ergot alkaloids are indole compounds that are biosynthetically derived from L-tryptophan and represent the largest group of fungal nitrogen metabolites found in nature. The common part of ergot alkaloids is lysergic acid. This [...] Read more.

Ergot is the spore form of the fungus Claviceps purpurea. Ergot alkaloids are indole compounds that are biosynthetically derived from L-tryptophan and represent the largest group of fungal nitrogen metabolites found in nature. The common part of ergot alkaloids is lysergic acid. This review shows the importance of lysergic acid as a representative of ergot alkaloids. The subject of ergot and its alkaloids is presented, with a particular focus on lysergic acid. All methods of total lysergic acid synthesis—through Woodward, Hendrickson, and Szantay intermediates and Heck coupling methods—are presented. The topic of biosynthesis is also discussed. Full article

(This article belongs to the Special Issue Synthetic Studies Aimed at Heterocyclic Organic Compounds)

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