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Examples of Fischer's base-triggered (3+2) cycloadditions and expanding the applicability scope of 3-isothiocyanato oxindoles.

This is the first example of the construction of harmaline-based spiropolycyclic scaffolds using harmaline-based N–C synthons and evaluation of 3cb as an anticancer agent.

C23H34O5, orthorhombic, P212121 (no. 19), a = 11.1838(3) Å, b = 11.7824(3) Å, c = 16.3160(5) Å, V = 2149.99(10) Å3, Z = 4, R g t ${R}_{\mathrm{g}\mathrm{t}}$ (F) = 0.0399, w R r e f $w{R}_{\mathrm{r}\mathrm{e}\mathrm{f}}$ (F 2) = 0.1097, T = 293 K.

C11H12BrNO2, monoclinic, P21/n (no. 14), a = 7.5143(12) Å, b = 11.8968(15) Å, c = 12.9852(13) Å, β = 105.575(14)°, V = 1118.2(3) Å3, Z = 4, R gt (F) = 0.0607, wR ref (F 2) = 0.1615, T = 293.00(10) K.

C16H12O3, monoclinic, P21/c (no. 14), a = 10.9636(14) Å, b = 12.1767(12) Å, c = 10.1557(13) Å, β = 116.588(16)°, V = 1212.4(3) Å3, Z = 4, Rgt (F) = 0.0366, wR ref (F 2) = 0.1019, T = 250.00(10) K.

This is the combination of three key pharmacophores through bispiro quaternary carbon atoms and evaluation of their anticancer activity.

We present a novel highly stereoselective Rh-catalyzed cyclopropanation of diazothiooxindoles with a broad range of α-functionalized styrenes, enabling facile access of chiral spirocyclopropylthiooxindoles in high to excellent enantiomeric excess.

The first example of the introduction of a spiroindanedione moiety into a spirobutyrolactone framework.

Herein a previously unreported trimethylindolenines serving as useful C-N synthons in [3+2] cycloaddition reactions of donor-acceptor 3-isothiocyanato oxindoles to build a library of spiro[oxindole-thioxoimidazolidine-indoline] hybrids is described. A wide range...

The O-site reactivity of difluoroenoxysilanes is disclosed for the first time, which enabled the direct construction of versatile gem-difluoroalkenes through an unprecedented highly efficient addition reaction with ketenes. A series of valuable gem-difluoroenol esters were achieved in good to excellent yields. The synthetic versatility of this protocol is further demonstrated by the gram-scale synthesis and good functional group tolerance.

Here, we demonstrate the first example of 3-isothiocyanato thiobutyrolactone serving as a useful building block in the Michael/cyclization reaction with alkylidene pyrazolones for the enantioselective construction of optically active structural bispiro[pyrazolone-thiobutyrolactone] skeletons containing three contiguous stereocenters with two spiroquaternary stereocenters. These products were smoothly afforded in up to 90% yield,20 : 1 dr and99% ee with chiral squaramide as the catalyst under mild conditions. Notably, this is also the first example of the merger of a spirocyclic pyrazolone scaffold with a spirocyclic thiobutyrolactone scaffold, potentially useful in medicinal chemistry.

Potentilla kleiniana Wight et Arn（PK, ‘Wu Pi Feng’ in Chinese） was recorded as Miao ethnic medicine for treatment of fever, cough, ulcer, and erysipelas for thousands years. This study aimed to evaluate the antiviral activity of four PK extracts and seven compounds by using HIV-1 protease (HIV-1 PR). In addition, Ultra-High Performance Liquid Chromatography and High Resolution Mass Spectrometry (UPLC-HRMS) was employed to identify the bioactive components. The toxicity assessment of the extracts was done before antiviral screening using a highly specific human aspartyl protease, renin protease by fluorimetric method. As a result, seven compounds and four extracts of PK inhibited HIV-1 PR with IC50 range from 0.009 to 0.36 mg/mL, and did not appreciably inhibit the general human protease renin. This study first demonstrated that four PK extracts, ellagic acid and ursolic acid potent inhibit HIV-1 protease, could be used as an efficacious drug candidate to treat SARS-CoV-2 infection.

Chiral spirolactones, including spiropropyllactones, spirobutyrolactones, and spirovalerolactones, are important heterocyclic frameworks that attracted the attention of organic and medicinal chemists because these motifs constitute the core structure of several natural products and bioactive molecules. The absolute configuration and the substituents on the fully substituted spirocyclic stereocenter of the lactone can potentially enhance specificity for ligand-protein binding and enhance bioavailability, potency, and metabolic stability. So, intensive attention from chemists has been paid to the synthetic methods leading to such prominent structural motifs. The synthetic methods can be divided into two main classes. The first approach takes advantage of the presence of the existing lactone structure and focuses on its functionalization. The second approach is the lactone framework constructed from various precursors in a direct spirolactonization reaction. In this review, for convenience in reading, the recent advances in the synthesis of spirolactones are summarized and discussed according to the two major organocatalytic asymmetric synthetic routes: (i) using the lactone-related frameworks as building blocks; and (ii) direct spirolactonization reaction using various reagents. This review also describes both the mechanisms and related transformations, and gives some insights into challenging issues in this research field, which will enlighten the future development of this field.

This review summarizes the advances in catalytic enantioselective reactions using CO2 as a C1 synthon, introduces major synthetic strategies and discusses their advantages and limitations, highlights the application of known protocols, and outlines the synthetic opportunities.

This review summarizes the advances in the catalytic enantioselective construction of vicinal quaternary carbon stereocenters, introduces major synthetic strategies and discusses their advantages and limitations, highlights the application of known protocols in the total synthesis of natural products, and outlines the synthetic opportunities., This review summarizes the advances in catalytic enantioselective construction of vicinal quaternary carbon stereocenters, introduces major synthetic strategies and discusses their advantages and limitations, and outlines the synthetic opportunities.

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The first allylic alkylation of difluoroenoxysilanes with MBH carbonates catalyzed by triethylenediamine (DABCO) is developed, which allows rapid access to multifunctional α-gem-difluoroketones with up to 97% yields. Moreover, the gram-scale synthesis and the diversifying transformation of products to valuable gem-difluorinated molecules highlight the practicality of this methodology.

A facile and efficient methodology was developed for the synthesis of multifunctional polycyclic spiropyrrolidine oxindoles bearing mesityl oxide unit via a three-component 1,3-dipolar cycloaddition reaction of dienones 2 with azomethine ylides (thermally generated in situ from isatin derivatives and proline or thioproline). Products bearing adjacent four chiral carbon centers were smoothly obtained in high yields (up to 98% yield) with diastereoselectivities up to >20:1. Furthermore, the key structural characteristic of the products of such a reaction is the natural product ingredient turmerone motif fused at the 3-position of the spirooxindole core, with varying degrees of substitution around it. In addition, their biological activity has been preliminarily demonstrated by in vitro evaluation against human prostate cancer cells PC-3, human lung cancer cells A549 and human leukemia cells K562 by the MTT-based assays, using the commercially available standard drugs Cisplatin as a positive control. These results suggested there is a trend that lipophilicity groups improve the potency, and also suggested an mesityl oxide moiety located in the polycyclic spiropyrrolidine oxindoles is beneficial for the activity. The results also demonstrated that most of the compounds showed considerable cytotoxicities to these three cell lines K562, A549 and PC-3, and indicated that polycyclic spiropyrrolidine oxindole analogs bearing mesityl oxide unit may be potential leads for further antitumor activity screenings.

A novel chiral phosphoric acid catalyst bearing two acidic phenolic hydroxyl groups was synthesized. Its catalytic activity as a chiral Brosted acid has been examined in the enantioselective Friedel-Crafts alkylation of indoles and enones as a model reaction. In comparison with the other chiral phosphoric acid catalysts, the reaction catalyzed by the novel chiral catalyst afforded the desired 3-substituted indoles in a higher enantioselectivity (up to 69% ee).

A facile and efficient methodology is developed for the synthesis of multifunctional polycyclic spiropyrrolidine oxindoles via a three-component 1,3-dipolar cycloaddition reaction of dienones (III) with azomethine ylides (thermally generated in situ from isatin derivatives and proline or thioproline).

A highly efficient and environmentally benign method for the synthesis of oxindoles featuring two contiguous quaternary carbon centers via an aldol reaction starting from various 3-substituted oxindoles has been established. A wide variety of such featured multi-substituted 1,3-indandione ring-fused 3-oxindole scaffolds were obtained smoothly in good yields (up to 98%) employing the most green of solvents, namely water, as reaction medium. Furthermore, their biological activity has been preliminarily demonstrated by in vitro evaluation against human prostate cancer cells PC-3, human lung cancer cells A549 and human leukemia cells K562 by MTT-based assays, using the commercially available standard drug, cisplatin, as a positive control. Gratifyingly, compounds 3s, 3u, 3y and 3c′ exhibited the best levels of in vitro inhibitory activity against human leukemia cells K562, which were almost 2.0, 2.8, 2.5 and 2.2 times, respectively, the activity of the positive control, cisplatin. Compound 3y had 2.7 times the activity of the positive control, cisplatin, against PC-3 cancer cells, and 3s, 3u and 3c′ showed levels of in vitro inhibitory activity against PC-3 cancer cells that were comparable to that of cisplatin. Compounds 3s, 3u and 3y had good inhibitory ability against human lung cancer cells A549. The results indicated that 1,3-indandione ring-fused 3-oxindole analogs may be useful leads for further biological screenings.