6.1 Thiol–Ene/Yne Click Reactions: A Powerful Tool Toward Diversity-Oriented Synthesis

2022 ◽  
Author(s):  
A. K. Sinha ◽  
R. Singh

AbstractThe clickable addition reaction between thiols and unsaturated compounds leading to the generation of (branched/linear) thioethers or (branched/linear) vinyl sulfides is known as the hydrothiolation reaction. Based upon the nature of unsaturation, i.e. double bond or triple bond, hydrothiolation reactions are classified as thiol–ene and thiol–yne click reactions, respectively. These reactions have emerged as a powerful and widely used strategy for the generation of carbon–sulfur bonds due to several associated benefits including versatile synthetic procedures, wide functional-group tolerance, high atom economy with few to no byproducts, and simple purification. The hydrothiolation reactions have numerous trapping applications in the fields of polymer chemistry, nanoengineering, pharmaceuticals, natural products, and perhaps most importantly in medicinal chemistry for the synthesis of many drugs and bioactive molecules.

2020 ◽  
Vol 24 (7) ◽  
pp. 709-745
Author(s):  
Meenakshi Singh ◽  
V. Ravichandiran ◽  
Yogesh P. Bharitkar ◽  
Abhijit Hazra

: Semi-synthesis, the way of preparing novel bioactive molecules via modification of compounds isolated from natural sources is very much useful nowadays in the drug discovery process. The modification is based on the reaction of functional group(s) present in a natural compound. Among the examples of functional group transformation, double bond modification is also common in the literature. Several reactions like hydrogenation, cyclopropanation, epoxidation, addition reaction (halogenations, hydroxylation), Michael addition, Heck reaction, cycloaddition, dipolar cycloaddition, etc. are employed for this purpose. In this review, we have tried to gather the reactions performed with several double bond containing classes of natural products like diterpenes, xanthones, sesquiterpene exomethylene lactones, diaryl heptanoids, steroidal lactones, triterpenoids, limonoids, and alkamides. Where available, the effects of transformations on the biological activities of the molecules are also mentioned.


Molecules ◽  
2021 ◽  
Vol 26 (21) ◽  
pp. 6398
Author(s):  
Fotini Moschona ◽  
Athena Vagena ◽  
Veroniki P. Vidali ◽  
Gerasimos Rassias

In general, the Pinder reaction concerns the reaction between an enolisable anhydride and an aldehyde proceeding initially through a Knoevenagel reaction followed by the ring closing process generating lactones with at least two chiral centers. These scaffolds are frequently present in natural products and synthetic bioactive molecules, hence it has attracted intense interest in organic synthesis and medicinal chemistry, particularly with respect to controlling the diastereo- and enantioselectivity. To the best of our knowledge, there has been only one attempt prior to this work towards the development of a catalytic enantioselective Pinder reaction. In our approach, we designed, synthesized, and tested dual chiral organocatalysts by combining BIMAH amines, (2-(α-(alkyl)methanamine)-1H-benzimidazoles, and a Lewis acid motif, such as squaramides, ureas and thioureas. The optimum catalyst was the derivative of isopropyl BIMAH bearing a bis(3,5-trifluoromethyl) thiourea, which afforded the Pinder products from various aromatic aldehydes with diastereomeric ratio >98:2 and enatioselectivity up to 92 ee%. Interestingly, the enantioselectivity of this catalyzed process is increased at higher concentrations and exhibits an isoinversion effect, namely an inverted "U" shaped dependency with respect to the temperature. Mechanistically, these features, point to a transition state involving an entropy-favored heterodimer interaction between a catalyst/anhydride and a catalyst/aldehyde complex when all other processes leading to this are much faster in comparison above the isoinversion temperature.


2020 ◽  
Vol 23 (2) ◽  
pp. 111-118
Author(s):  
Zhiping Che ◽  
Jinming Yang ◽  
Di Sun ◽  
Yuee Tian ◽  
Shengming Liu ◽  
...  

Background: It is one of the effective ways for pesticide innovation to develop new insecticides from natural products as lead compounds. Quinine, the main alkaloid in the bark of cinchona tree as well as in plants in the same genus, is recognized as a safe and potent botanical insecticide to many insects. The structural modification of quinine into 9R-acyloxyquinine derivatives is a potential approach for the development of novel insecticides, which showed more toxicity than quinine. However, there are no reports on the insecticidal activity of 9Racyloxyquinine derivatives to control Mythimna separata. Methods: Endeavor to discover biorational natural products-based insecticides, 20 novel 9Racyloxyquinine derivatives were prepared and assessed for their insecticidal activity against M. separata in vivo by the leaf-dipping method at 1 mg/mL. Results: Among all the compounds, especially derivatives 5i, 5k and 5t exhibited the best insecticidal activity with final mortality rates of 50.0%, 57.1%, and 53.6%, respectively. Conclusion: Overall, a free 9-hydroxyl group is not a prerequisite for insecticidal activity and C9- substitution is well tolerated; modification of out-ring double-bond is acceptable, and hydrogenation of double-bond enhances insecticidal activity; Quinine ring is essential and open of it is not acceptable. These preliminary results will pave the way for further modification of quinine in the development of potential new insecticides.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Shi Cao ◽  
Wei Hong ◽  
Ziqi Ye ◽  
Lei Gong

AbstractThe direct and selective C(sp3)-H functionalization of cycloalkanes and alkanes is a highly useful process in organic synthesis owing to the low-cost starting materials, the high step and atom economy. Its application to asymmetric catalysis, however, has been scarcely explored. Herein, we disclose our effort toward this goal by incorporation of dual asymmetric photocatalysis by a chiral nickel catalyst and a commercially available organophotocatalyst with a radical relay strategy through sulfur dioxide insertion. Such design leads to the development of three-component asymmetric sulfonylation involving direct functionalization of cycloalkanes, alkanes, toluene derivatives or ethers. The photochemical reaction of a C(sp3)-H precursor, a SO2 surrogate and a common α,β-unsaturated carbonyl compound proceeds smoothly under mild conditions, delivering a wide range of biologically interesting α-C chiral sulfones with high regio- and enantioselectivity (>50 examples, up to >50:1 rr and 95% ee). This method is applicable to late-stage functionalization of bioactive molecules, and provides an appealing access to enantioenriched compounds starting from the abundant hydrocarbon compounds.


2021 ◽  
Vol 21 (17) ◽  
pp. 1517-1518
Author(s):  
Dharmendra Kumar Yadav

The discovery and utilization of novel metabolites from natural sources are gaining momentum in the present era. The drug discovery programs have witnessed a remarkable shift from conventional medicines to exploiting natural products and their “value addition”, for treating lifethreatening diseases. The global outbreak of life-threatening diseases namely Ebola, SARS,including infections of the bloodstream (bacteremia), heart valves (endocarditis), lungs (pneumonia), and brain (meningitis) and AIDS calls for a more targeted approach to effectively combat the emerging diseases. In the present scenario, natural products and their extracts are being explored extensively for the treatment of various life threatening diseases. In this thematic issue, several review articles contributed by the scientist and researchers in the different areas of medicinal chemistry, synthetic chemistry, new emerging multi-drug targets were collected. This issue begins with a review article on the “Chemistry and Pharmacology of Natural Catechins from Camellia sinensis as anti-MRSA agents” by Gaur et al. and focuses on the spread of MRSA strains is of great concern because of limited treatment options for staphylococcal infections, since these strains are resistant to the entire class of β-lactam antibiotics. In addition, MRSA exhibits resistance to other classes of antimicrobial agents such as fluoroquinolones, cephalosporins, aminoglycosides, macrolide and even glycopeptides (vancomycin and teicoplanine), leading to the emergence of resistant strains such as glycopeptide intermediate (GISA) and resistant strain (GRSA) of S. aureus. In this review, chemical constituents responsible for the anti-MRSA activity of tea are explored [1]. The next article of this issue is a review article on the “Recent Advancements in the Synthesis and Chemistry of Benzofused Nitrogen- and Oxygen-based Bioactive Heterocycles” by Sharma et al. which focuses on medicinal importance of these bioactive benzo-fused heterocycles; special attention has been given to their synthesis as well as medicinal/pharmaceutical properties in detail [2]. “Trends in pharmaceutical design of Endophytes as anti-infective,” by Tiwari et al., is the third article in this issue. The review focused on the meta-analysis of bioactive metabolite production from endophytes, extensively discussing the bioprospection of natural products for pharmaceutical applications. In light of the emerging importance of endophytes as antiinfective agents, an exploration of the pharmaceutical design of novel chemical entities and analogues has enabled efficient and cost-effective drug discovery programs. However, bottlenecks in endophytic biology and research requires a better understanding of endophytic dynamics and mechanism of bioactive metabolite production towards a sustainable drug discovery program [3]. The last article of this issue is also research article on “Recent development of tetrahydro-quinoline/isoquinoline based compounds as anticancer agents” by Yadav et al. The article reported the synthesis of potent tetrahydroquinoline/isoquinoline molecules of the last 10 years with their anticancer properties in various cancer cell lines and stated their half-maximal inhibitory concentration (IC50). In addition, we also considered the discussion of molecular docking and structural activity relationship wherever provided to understand the possible mode of activity an target involved and structural features responsible for the better activity, so the reader can directly find detail for designing new anticancer agents. [4]. Finally I would like to thank all authors who contributed to this issue, titled “Recent advances on small molecule medicinal chemistry to treat human diseases”.


2021 ◽  
Vol 25 ◽  
Author(s):  
Pedro Alves Bezerra Morais ◽  
Carla Santana Francisco ◽  
Heberth de Paula ◽  
Rayssa Ribeiro ◽  
Mariana Alves Eloy ◽  
...  

: Historically, the medicinal chemistry is concerned with the approach of organic chemistry to new drug synthesis. Considering the fruitful collections of new molecular entities, the dedicated efforts for medicinal chemistry are rewarding. Planning and search of new and applicable pharmacologic therapies involve the altruistic nature of the scientists. Since the 19th century, notoriously the application of isolated and characterized plant-derived compounds in modern drug discovery and in various stages of clinical development highlight its viability and significance. Natural products influence a broad range of biological processes, covering transcription, translation, and post-translational modification and being effective modulators of almost all basic cellular processes. The research of new chemical entities through “click chemistry” continuously opens up a map for the remarkable exploration of chemical space in towards leading natural products optimization by structure-activity relationship. Finally, here in this review, we expect to gather a broad knowledge involving triazolic natural products derivatives, synthetic routes, structures, and their biological activities.


Author(s):  
Mengyu Qiu ◽  
Xuegang Fu ◽  
Peng Fu ◽  
Jianhui Huang

N-heterocycles can be found in natural products and drug molecules, which are indispensable components in the area of organic synthesis, medicinal chemistry and material science. The construction of these N-containing...


MedChemComm ◽  
2016 ◽  
Vol 7 (11) ◽  
pp. 2063-2075 ◽  
Author(s):  
Federica Pellati ◽  
Giulio Rastelli

This review focuses on novel classes of natural products whose structures have not yet been thoroughly explored for medicinal chemistry purposes. These novel chemotypes may be useful starting points to develop compounds that alter Hsp90 functionvianovel mechanisms.


2009 ◽  
Vol 17 (6) ◽  
pp. 2120 ◽  
Author(s):  
David Newman ◽  
Gordon Cragg

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