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18 pages, 1873 KiB

Open AccessArticle

Synthesis of 5,6-Dihydrophenanthridines via Palladium-Catalyzed Intramolecular Dehydrogenative Coupling of Two Aryl C−H Bonds

by Meng-Yue Wang, Xue-Qing Zhu, Bao-Yin Zhao, Hong-Xia Zhang, Yong-Qiang Wang and Qiong Jia

Molecules 2023, 28(6), 2498; https://doi.org/10.3390/molecules28062498 - 9 Mar 2023

Cited by 2 | Viewed by 1686

Abstract

5,6-Dihydrophenanthridines are common aza heterocycle frameworks of natural products and pharmaceuticals. Herein, we reported the first palladium-catalyzed intramolecular C−H/C−H dehydrogenative coupling reaction of two simple arenes to generate 5,6-dihydrophenanthridines. The approach features a broad substrate scope and good tolerance of functional groups, offering [...] Read more.

5,6-Dihydrophenanthridines are common aza heterocycle frameworks of natural products and pharmaceuticals. Herein, we reported the first palladium-catalyzed intramolecular C−H/C−H dehydrogenative coupling reaction of two simple arenes to generate 5,6-dihydrophenanthridines. The approach features a broad substrate scope and good tolerance of functional groups, offering an efficient alternative synthesis route for important 5,6-dihydrophenanthridine compounds. Full article

(This article belongs to the Special Issue Chemical Synthesis of Natural Products)

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12 pages, 1554 KiB

Open AccessArticle

Total Synthesis of Lineaflavones A, C, D, and Analogues

by Rui Wang, Yu Fu, Ran Ma, Hongzhen Jin and Wei Zhao

Molecules 2023, 28(5), 2373; https://doi.org/10.3390/molecules28052373 - 4 Mar 2023

Viewed by 1983

Abstract

The first total synthesis of lineaflavones A, C, D, and their analogues has been accomplished. The key synthetic steps include aldol/oxa-Michael/dehydration sequence reactions to assemble the tricyclic core, Claisen rearrangement and Schenck ene reaction to construct the key intermediate, and selective substitution or [...] Read more.

The first total synthesis of lineaflavones A, C, D, and their analogues has been accomplished. The key synthetic steps include aldol/oxa-Michael/dehydration sequence reactions to assemble the tricyclic core, Claisen rearrangement and Schenck ene reaction to construct the key intermediate, and selective substitution or elimination of tertiary allylic alcohol to obtain natural compounds. In addition, we also explored five new routes to synthesize fifty-three natural product analogues, which can contribute to a systematic structure–activity relationship during biological evaluation. Full article

(This article belongs to the Special Issue Chemical Synthesis of Natural Products)

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11 pages, 925 KiB

Open AccessArticle

Enantioselective Total Synthesis of (R,R)-Blumenol B and d₉-(R,R)-Blumenol B

by Shi Min Tan, Shaun W. P. Rees, Rebecca E. Jelley, Jin Wang, Bruno Fedrizzi and David Barker

Molecules 2022, 27(21), 7294; https://doi.org/10.3390/molecules27217294 - 27 Oct 2022

Viewed by 1800

Abstract

C₁₃-norisoprenoids are of particular importance to grapes and wines, as these molecules influence wine aroma and have been shown to significantly contribute to the distinct character of various wine varieties. Blumenol B is a putative precursor to a number of important [...] Read more.

C₁₃-norisoprenoids are of particular importance to grapes and wines, as these molecules influence wine aroma and have been shown to significantly contribute to the distinct character of various wine varieties. Blumenol B is a putative precursor to a number of important wine aroma compounds, including the well-known compounds theaspirone and vitispirane. The enantioselective synthesis of (R,R)-blumenol B from commercially available 4-oxoisophorone was achieved using a short and easily scaleable route, which was then successfully applied to the synthesis of poly-deuterated d9-blumenol B. Full article

(This article belongs to the Special Issue Chemical Synthesis of Natural Products)

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10 pages, 1085 KiB

Open AccessArticle

Asymmetric Synthesis of Contact Sex Pheromone of Tetropium fuscum and Its Enantiomer

by Xueyang Wang, Jianan Wang, Fengbo Ma, Qinghua Bian, Min Wang and Jiangchun Zhong

Molecules 2022, 27(20), 6897; https://doi.org/10.3390/molecules27206897 - 14 Oct 2022

Cited by 2 | Viewed by 1551

Abstract

Tetropium fuscum is a harmful forest pest and attacks spruces. The contact sex pheromone of this pest, (S)-11-methyl-heptacosane, and its enantiomer were synthesized via Evans’ chiral auxiliaries. The key steps of this approach included acylation of carboxylic acid, diastereoselective methylation of [...] Read more.

Tetropium fuscum is a harmful forest pest and attacks spruces. The contact sex pheromone of this pest, (S)-11-methyl-heptacosane, and its enantiomer were synthesized via Evans’ chiral auxiliaries. The key steps of this approach included acylation of carboxylic acid, diastereoselective methylation of oxazolidinone amide, and Wittig coupling of the aldehyde with chiral phosphonium salt. The synthetic pheromones would have potential utility in the control of this pest. Full article

(This article belongs to the Special Issue Chemical Synthesis of Natural Products)

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8 pages, 1018 KiB

Open AccessArticle

A Concise Synthesis of Sacidumlignan B

by Zhiyuan Zhuang, Zhenbiao Luo, Sichen Yao, Yawen Wang and Yu Peng

Molecules 2022, 27(18), 5775; https://doi.org/10.3390/molecules27185775 - 7 Sep 2022

Cited by 4 | Viewed by 1589

Abstract

A short synthesis of racemic Sacidumlignan B was achieved for the first time. The key steps included a formal reductive coupling between the diaryl ketone and the crotyl bromide, and the subsequent Friedel–Crafts cyclization, which led to an efficient construction of dihydronaphthalene skeleton [...] Read more.

A short synthesis of racemic Sacidumlignan B was achieved for the first time. The key steps included a formal reductive coupling between the diaryl ketone and the crotyl bromide, and the subsequent Friedel–Crafts cyclization, which led to an efficient construction of dihydronaphthalene skeleton in this 2,7′-cyclolignan natural product. Full article

(This article belongs to the Special Issue Chemical Synthesis of Natural Products)

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8 pages, 2362 KiB

Open AccessArticle

Tandem Transesterification–Esterification Reactions Using a Hydrophilic Sulfonated Silica Catalyst for the Synthesis of Wintergreen Oil from Acetylsalicylic Acid Promoted by Microwave Irradiation

by Sandro L. Barbosa, David Lee Nelson, Milton de S. Freitas, Wallans Torres Pio dos Santos, Stanlei I. Klein, Giuliano C. Clososki, Franco J. Caires and Alexandre P. Wentz

Molecules 2022, 27(15), 4767; https://doi.org/10.3390/molecules27154767 - 26 Jul 2022

Viewed by 3861

Abstract

SiO₂–SO₃H, with a surface area of 115 m²/g and pore volume of 0.38 cm³g⁻¹, and 1.32 mmol H⁺/g was used as a 20% w/w catalyst for the preparation of [...] Read more.

SiO₂–SO₃H, with a surface area of 115 m²/g and pore volume of 0.38 cm³g⁻¹, and 1.32 mmol H⁺/g was used as a 20% w/w catalyst for the preparation of methyl salicylate (wintergreen oil or MS) from acetylsalicylic acid (ASA). A 94% conversion was achieved in a microwave reactor over 40 min at 120 °C in MeOH. The resulting crude product was purified by flash chromatography. The catalyst could be reused three times. Full article

(This article belongs to the Special Issue Chemical Synthesis of Natural Products)

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10 pages, 5997 KiB

Open AccessFeature PaperArticle

Trityl Cation-Catalyzed Hosomi-Sakurai Reaction of Allylsilane with β,γ-Unsaturated α-Ketoester to Form γ,γ-Disubstituted α-Ketoesters

by Zubao Gan, Deyun Cui, Hongyun Zhang, Ying Feng, Liying Huang, Yingying Gui, Lu Gao and Zhenlei Song

Molecules 2022, 27(15), 4730; https://doi.org/10.3390/molecules27154730 - 24 Jul 2022

Cited by 2 | Viewed by 2019

Abstract

(Ph₃C)[BPh(^F)₄]-catalyzed Hosomi-Sakurai allylation of allylsilanes with β,γ-unsaturated α-ketoesters has been developed to give γ,γ-disubstituted α-ketoesters in high yields with excellent chemoselectivity. Preliminary mechanistic studies suggest that trityl cation dominates the catalysis, while the silyl cation plays a minor role. Full article

(This article belongs to the Special Issue Chemical Synthesis of Natural Products)

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8 pages, 3257 KiB

Open AccessArticle

Na₂S-Mediated One-Pot Selective Deoxygenation of α-Hydroxyl Carbonyl Compounds including Natural Products

by Xiaobo Xu, Leyu Yan, Zhi-Kai Zhang, Bingqing Lu, Zhuangwen Guo, Mengyue Chen and Zhong-Yan Cao

Molecules 2022, 27(15), 4675; https://doi.org/10.3390/molecules27154675 - 22 Jul 2022

Cited by 3 | Viewed by 2594

Abstract

A practical method for the deoxygenation of α-hydroxyl carbonyl compounds under mild reaction conditions is reported here. The use of cheap and easy-to-handle Na₂S·9H₂O as the reductant in the presence of PPh₃ and N-chlorosuccinimide (NCS) enables the [...] Read more.

A practical method for the deoxygenation of α-hydroxyl carbonyl compounds under mild reaction conditions is reported here. The use of cheap and easy-to-handle Na₂S·9H₂O as the reductant in the presence of PPh₃ and N-chlorosuccinimide (NCS) enables the selective dehydroxylation of α-hydroxyl carbonyl compounds, including ketones, esters, amides, imides and nitrile groups. The synthetic utility is demonstrated by the late-stage deoxygenation of bioactive molecule and complex natural products. Full article

(This article belongs to the Special Issue Chemical Synthesis of Natural Products)

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Review

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15 pages, 2907 KiB

Open AccessReview

Deconstructive and Divergent Synthesis of Bioactive Natural Products

by Si-Hua Hou, Feng-Fan Zhou, Yi-Hang Sun and Quan-Zhe Li

Molecules 2023, 28(17), 6193; https://doi.org/10.3390/molecules28176193 - 22 Aug 2023

Cited by 3 | Viewed by 2188

Abstract

Natural products play a key role in innovative drug discovery. To explore the potential application of natural products and their analogues in pharmacology, total synthesis is a key tool that provides natural product candidates and synthetic analogues for drug development and potential clinical [...] Read more.

Natural products play a key role in innovative drug discovery. To explore the potential application of natural products and their analogues in pharmacology, total synthesis is a key tool that provides natural product candidates and synthetic analogues for drug development and potential clinical trials. Deconstructive synthesis, namely building new, challenging structures through bond cleavage of easily accessible moieties, has emerged as a useful design principle in synthesizing bioactive natural products. Divergent synthesis, namely synthesizing many natural products from a common intermediate, can improve the efficiency of chemical synthesis and generate libraries of molecules with unprecedented structural diversity. In this review, we will firstly introduce five recent and excellent examples of deconstructive and divergent syntheses of natural products (2021–2023). Then, we will summarize our previous work on the deconstructive and divergent synthesis of natural products to demonstrate the high efficiency and simplicity of these two strategies in the field of total synthesis. Full article

(This article belongs to the Special Issue Chemical Synthesis of Natural Products)

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20 pages, 5021 KiB

Open AccessReview

Potent Antibiotic Lemonomycin: A Glimpse of Its Discovery, Origin, and Chemical Synthesis

by Shunan Tao, Yang Wang, Ran Hong and Sha-Hua Huang

Molecules 2022, 27(13), 4324; https://doi.org/10.3390/molecules27134324 - 5 Jul 2022

Cited by 3 | Viewed by 2943

Abstract

Lemonomycin (1) was first isolated from the fermentation broth of Streptomyces candidus in 1964. The complete chemical structure was not elucidated until 2000 with extensive spectroscopic analysis. Lemonomycin is currently known as the only glycosylated tetrahydroisoquinoline antibiotic. Its potent antibacterial activity [...] Read more.

Lemonomycin (1) was first isolated from the fermentation broth of Streptomyces candidus in 1964. The complete chemical structure was not elucidated until 2000 with extensive spectroscopic analysis. Lemonomycin is currently known as the only glycosylated tetrahydroisoquinoline antibiotic. Its potent antibacterial activity against Staphylococcus aureus and Bacillus subtilis and complex architecture make it an ideal target for total synthesis. In this short review, we summarize the research status of lemonomycin for biological activity, biosynthesis, and chemical synthesis. The unique deoxy aminosugar-lemonose was proposed to play a crucial role in biological activity, as shown in other antibiotics, such as arimetamycin A, nocathiacin I, glycothiohexide α, and thiazamycins. Given the self-resistance of the original bacterial host, the integration of biosynthesis and chemical synthesis to pursue efficient synthesis and further derivatization is in high demand for the development of novel antibiotics to combat antibiotic-resistant infections. Full article

(This article belongs to the Special Issue Chemical Synthesis of Natural Products)

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