First synthesis of 10 alpha-(trifluoromethyl)deoxoartemisinin

11-Azaartemisinin derivatives bearing halogenated aromatic moieties: Potent anticancer agents with high tumor selectivity

While artemisinin and its derivatives, including 11-azaartemisinin-based compounds, have shown promising anticancer activity, the integration of halogens into aromatic structures can amplify drug potency, metabolic stability, and selectivity. Herein, we present the synthesis of new novel 11-azaartemisinin derivatives bearing halogenated aromatic moieties connected via 1,2,3-triazole bridges and evaluate their anticancer activities against three human tumor cell lines: epidermoid carcinoma (KB), hepatocellular carcinoma (HepG2), and human lung adenocarcinoma (A549). Among the synthesized compounds, six of them (8c-h) displayed good to excellent antiproliferative activity in the low micromolar range across all three human cancer cell lines. In general, the m-bromide (8c) and m-iodide (8d) compounds exhibited superior anticancer activities compared to their o- and p-analogs, as well as the m-chloride and m-fluoride compounds. The most promising m-Br compound (8c) displayed 50 % inhibition of KB, HepG2, and A549 cell growth at concentrations of 7.7, 42.5, and 15.5 μM, respectively. Notably, the m-Br compound (8c) exhibited approximately 32-, 6-, and 16-fold lower activity in normal cells (Hek293) compared to KB, HepG2, and A549 tumor cells, respectively, indicating a significant tumor-selectivity.

Recent Advances in Enantioselective Organocatalytic Reactions Enabled by NHCs Containing Triazolium Motifs

N-Heterocyclic carbenes (NHCs) containing triazolium motifs have emerged as a powerful tool in organocatalysis. Recently, various NHC pre-catalyst mediated organic transformations have been developed successfully. This article aims to compile the current state of knowledge on NHC-triazolium catalysed enantioselective name reactions and introduce newly developed catalytic methods. Furthermore, this review article framework provides an excellent opportunity to highlight some of the unique applications of these catalytic procedures in the natural product synthesis of biologically active compounds, notably the wide range of preparation of substituted chiral alcohols, and their derivatives. This article provides an overview of chiral NHC triazolium-catalyst libraries synthesis and their catalytic application in enantioselective reactions.

Exploration of artemisinin derivatives and synthetic peroxides in antimalarial drug discovery research

Malaria is a life-threatening infectious disease caused by protozoal parasites belonging to the genus Plasmodium. It caused an estimated 405,000 deaths and 228 million malaria cases globally in 2018 as per the World Malaria Report released by World Health Organization (WHO) in 2019. Artemisinin (ART), a "Nobel medicine" and its derivatives have proven potential application in antimalarial drug discovery programs. In this review, antimalarial activity of the most active artemisinin derivatives modified at C-10/C-11/C-16/C-6 positions and synthetic peroxides (endoperoxides, 1,2,4-trioxolanes, 1,2,4-trioxanes, and 1,2,4,5-tetraoxanes) are systematically summarized. The developmental trend of ART derivatives, and cyclic peroxides along with their antimalarial activity and how the activity is affected by structural variations on different sites of the compounds are discussed. This compilation would be very useful towards scaffold hopping aimed at avoiding the unnecessary complexity in cyclic peroxides, and ultimately act as a handy resource for the development of potential chemotherapeutics against Plasmodium species.

Artemisinin-derived antimalarial endoperoxides from bench-side to bed-side: Chronological advancements and future challenges

According to WHO World Malaria Report (2018), nearly 219 million new cases of malaria occurred and a total no. of 435 000 people died in 2017 due to this infectious disease. This is due to the rapid spread of parasite-resistant strains. Artemisinin (ART), a sesquiterpene lactone endoperoxide isolated from traditional Chinese herb Artemisia annua, has been recognized as a novel class of antimalarial drugs. The 2015 "Nobel Prize in Physiology or Medicine" was given to Prof Dr Tu Youyou for the discovery of ART. Hence, ART is termed as "Nobel medicine." The present review article accommodates insights from the chronological advancements and direct statistics witnessed during the past 48 years (1971-2019) in the medicinal chemistry of ART-derived antimalarial endoperoxides, and their clinical utility in malaria chemotherapy and drug discovery.

Current scenario of artemisinin and its analogues for antimalarial activity

Human malaria, one of the most striking, reemerging infectious diseases, is caused by several types of Plasmodium parasites. Whilst advances have been made in lowering the numbers of cases and deaths, it is clear that a strategy based solely on disease control year on year, without reducing transmission and ultimately eradicating the parasite, is unsustainable. Natural products have served as a template for the design and development of antimalarial drugs currently in the clinic or in the development phase. Artemisinin combine potent, rapid antimalarial activity with a wide therapeutic index and an absence of clinically important resistance. The alkylating ability of artemisinin and its semi-synthetic analogues toward heme related to their antimalarial efficacy are underlined. Although impressive results have already been achieved in malaria research, more systematization and concentration of efforts are required if real breakthroughs are to be made. This review will concisely cover the clinical, preclinical antimalarial and current updates in artemisinin based antimalarial drugs. Diverse classes of semi-synthetic analogs of artemisinin reported in the last decade have also been extensively studied. The experience gained in this respect is discussed.

Preparation ofN-Sulfonyl- andN-Carbonyl-11-Azaartemisinins with Greatly Enhanced Thermal Stabilities: in vitro Antimalarial Activities

As the clinically used artemisinins do not withstand the thermal stress testing required to evaluate shelf life for storage in tropical countries where malaria is prevalent, there is a need to develop thermally more robust artemisinin derivatives. Herein we describe the attachment of electron-withdrawing arene- and alkanesulfonyl and -carbonyl groups to the nitrogen atom of the readily accessible Ziffer 11-azaartemisinin to provide the corresponding N-sulfonyl- and -carbonylazaartemisinins. Two acylurea analogues were also prepared by treatment of the 11-azaartemisinin with arylisocyanates. Several of the N-sulfonylazaartemisinins have melting points above 200 degrees C and possess substantially greater thermal stabilities than the artemisinins in current clinical use, with the antimalarial activities of several of the arylsulfonyl derivatives being similar to that of artesunate against the drug-sensitive 3D7 clone of the NF54 isolate and the multidrug-resistant K1 strain of P. falciparum. The compounds possess relatively low cytotoxicities. The carbonyl derivatives are less crystalline than the N-sulfonyl derivatives, but are generally more active as antimalarials. The N-nitroarylcarbonyl and arylurea derivatives possess sub-ng ml(-1) activities. Although several of the azaartemisinins possess log P values below 3.5, the compounds have poor aqueous solubility (<1 mg L(-1) at pH 7). The greatly enhanced thermal stability of our artemisinins suggests that strategic incorporation of electron-withdrawing polar groups into both new artemisinin derivatives and totally synthetic trioxanes or trioxolanes may assist in the generation of practical new antimalarial drugs which will be stable to storage conditions in the field, while retaining favorable physicochemical properties.

Transition-Metal-Catalyzed Group Transfer Reactions for Selective C−H Bond Functionalization of Artemisinin

Three types of novel artemisinin derivatives have been synthesized through transition-metal-catalyzed intramolecular carbenoid and nitrenoid C-H bond insertion reactions. With rhodium complexes as catalysts, lactone 11 was synthesized via carbene insertion reaction at the C16 position in 90% yield; oxazolidinone 13 was synthesized via nitrene insertion reaction at the C10 position in 87% yield based on 77% conversion; and sulfamidate 14 was synthesized via nitrene insertion reaction at the C8 position in 87% yield.

Fluoroartemisinins: Metabolically More Stable Antimalarial Artemisinin Derivatives

This report is an overview on the design, preparation, and evaluation of metabolically stable artemisinins, using fluorine substitution. The chemical challenges encountered for the incorporation of fluorine-containing elements and the preparation of a large range of 10-trifluoromethyl artemisinin derivatives are detailed. Impact of the fluorine substitution on the antimalarial activity is also highlighted. Preclinical data of lead compounds, and evidence for their strong and prolonged antimalarial activity are presented.

Fluoroartemisinin: trifluoromethyl analogues of artemether and artesunate

The synthesis of a series of C-10 trifluoromethyl ethers of artemisinin has been achieved from key bromide 8, itself carried out in two steps from artemisinin. The substitution of 8 with methanol, ethanol, or succinic acid allowed the access of C-10 CF(3) analogues of beta-artemether, beta-arteether, or artesunate, respectively, in good yields (up to 89%). The presence of the CF(3) group at C-10 of artemisinin clearly increased the chemical stability under simulated stomach acid conditions. For example, the CF(3) analogue of arteether was found to be around 45 times more stable than arteether itself. The influence of the CF(3) moiety on biological activity was also highlighted. CF(3) analogues of artemether and arteether exhibited a high in vivo antimalarial activity on mice infected with Plasmodium berghei NK173, with a complete clearance of the parasitemia during the entire observation period (25 days).

Preparation of 10-Trifluoromethyl Artemether and Artesunate. Influence of Hexafluoropropan-2-ol on Substitution Reaction

To prepare 10-trifluoromethyl analogues of important antimalarials such as artemether and artesunate, the substitution reaction of the 10-trifluoromethyl hemiketal 6 and bromide 4 derived from artemisinin was investigated. While 6 appeared to be unreactive under various conditions, bromide 4 could easily undergo substitution with methanol under electrophilic assistance or noncatalyzed conditions. Optimization of the reaction revealed the role of CH(2)Cl(2) as solvent to avoid the competitive elimination process and the crucial influence of hexafluoro-2-propanol (HFIP) in increasing the rate and the stereoselectivity of the substitution reaction (de >98%). The efficiency of this reaction was exemplified with various alcohols and carboxylates (yield up to 89%).

Structure-activity relationships of the antimalarial agent artemisinin. 8. design, synthesis, and CoMFA studies toward the development of artemisinin-based drugs against leishmaniasis and malaria

Artemisinin (1) and its analogues have been well studied for their antimalarial activity. Here we present the antimalarial activity of some novel C-9-modified artemisinin analogues synthesized using artemisitene as the key intermediate. Further, antileishmanial activity of more than 70 artemisinin derivatives against Leishmania donovani promastigotes is described for the first time. A comprehensive structure-activity relationship study using CoMFA is discussed. These analogues exhibited leishmanicidal activity in micromolar concentrations, and the overall activity profile appears to be similar to that against malaria. Substitution at the C-9beta position was shown to improve the activity in both cases. The 10-deoxo derivatives showed better activity compared to the corresponding lactones. In general, compounds with C-9alpha substitution exhibited lower antimalarial as well as antileishmanial activities compared to the corresponding C-9beta analogues. The importance of the peroxide group for the observed activity of these analogues against leishmania was evident from the fact that 1-deoxyartemisinin analogues did not exhibit antileishmanial activity. The study suggests the possibility of developing artemisinin analogues as potential drug candidates against both malaria and leishmaniasis.

Alkylation of manganese(II) tetraphenylporphyrin by antimalarial fluorinated artemisinin derivatives

The alkylating properties of two artemisinin derivatives bearing a trifluoromethyl substituent at C10 were evaluated toward manganese(II) tetraphenylporphyrin, considered as a heme model. Chlorin-type covalent adducts were obtained by alkylation of the porphyrin ring by C-centered radicals derived from reductive activation of the peroxide function of the drugs.