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Two undescribed ent -kaurene diterpenes, named guidongnins I ( 1 ) and J ( 2 ), were isolated from the medicinal plant Isodon rubescens . Compound 1 was determined to contain an unprecedented 23 carbons in the skeleton by bearing an extra isopropyl group at C-17 out of the diterpenoid parent structure, and compound 2 was the first example of 6,7- seco -7,20-olide- ent -kaurenes with two fused-tetrahydrofuran rings formed between C-6 and C-19/C-20 through oxygen bridges. Their structures, including their absolute configurations, were determined using the analyses of the spectroscopic and X-ray diffraction data. Guidongnins I ( 1 ) and J ( 2 ) were assessed for their anti-cancer activities against the growth of various cancer cell lines, and 2 displayed cytotoxic potency against HepG2 at IC 50 27.14 ± 3.43 μM.

Isodon amethystoides (Lamiaceae) is a popular plant in folk medicine in the southern provinces of China. Our phytochemical investigation of the twigs and leaves of this plant led to the discovery of five new diterpenoids with isopimarane and 3,4-seco isopimarane scaffolds [isoamethinols A-E (1-5)], along with the known compound 3,4-seco isopimara-4(18),7,15-triene-3-oic acid methylester (6). The chemical structures of these compounds, including the absolute configurations of the new diterpenoids, were determined by comprehensive spectroscopic analyses and single crystal X-ray diffraction measurements. These compounds were evaluated for their biological activities against a panel of human cancer cell lines, gram-positive bacterial strains and HIV. Notably, the 3,4-seco-isopimarane isoamethinol D (4) showed toxicity to the cervical Hela cancer (Hela) cells with an IC 50 value of 27.21 μM and the lung (A549) cancer cells with an IC 50 value of 21.47 μM. Compound 4 also exhibited mild antimicrobial activity against the oral bacterial strain Streptococcus mutans. These findings suggested that the diterpenoids with a 3,4-seco-isopimarane diterpenoids isolated from I. amethystoides could provide a novel structure scaffold for the discovery of anticancer and antimicrobial compounds., (© 2022. The Author(s).)

In order to discover more promising antifungal and antibacterial agents, a series of new derivatives were designed and synthesized by structure modification based on the naturally occurring antimicrobial compound lophanic acid. The structures of all the target compounds were well characterized by spectroscopic data. The stereochemistry of these compounds was further determined through the X-ray diffraction analysis of 6a. The synthetic compounds were evaluated for their antimicrobial activities against filamentous fungi ( T. rubrum, T. mentagrophytes ), yeasts ( C. neoformans, C. albicans ) and Gram-positive and Gram-negative bacteria ( MRSA, S. mutans, S. sobrinus, and E. coli ). Among them, 3d and 3i are found as the most promising leads that showed potent inhibitory effects against all the tested fungal and bacterial strains except for E. coli . The presence of the C-20 carboxylic ester groups and the free hydroxy group at C-13 was found to be essential for the antifungal and antibacterial activities of the lophanic acid derivatives.

A chemo- and diastereo-selective (3 + 2) cycloaddition reacition between Donor-Acceptor (D-A) cyclopropanes and α,β-unsaturated enamides is developed for efficient access to spiro(cyclopentane-1,3'-indoline) derivatives. Simple, inexpensive and readily available NaOH is used as the sole catalyst for this process. A broad range of D-A cyclopropanes could be used as the C-3 synthons to react with oxindole-derived α,β-unsaturated enamides. The structurally sophisticated spiro(cyclopentane-1,3'-indoline) derivatives bearing up to 3 adjacent chiral centers are afforded in excellent yields as single diastereomers., (Copyright © 2020 Zhu, Pan, Mou, Zhou, Pan and Jin.)

The combined use of gold as transition metal catalyst and N-heterocyclic carbene (NHC) as organic catalyst in the same solution for relay catalytic reactions was disclosed. The ynamide substrate was activated by gold catalyst to form unsaturated ketimine intermediate that subsequently reacted with the enals (via azolium enolate intermediate generated with NHC) effectively to form bicyclic lactam products with excellent diastereo- and enantio-selectivities. The gold and NHC coordination and dissociation can be dynamic and tunable events, and thus allow the co-existence of both active metal and carbene organic catalysts in appreciable concentrations, for the dual catalytic reaction to proceed., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A catalyst- and metal-free electrochemical hydrodehalogenation of aryl halides is disclosed. Our reaction by a flexible protocol is operated in an undivided cell equipped with an inexpensive graphite rod anode and cathode. Trialkylamines nBu 3 N/Et 3 N behave as effective reductants and hydrogen atom donors for this electrochemical reductive reaction. Various aryl and heteroaryl bromides worked effectively. The typically less reactive aryl chlorides and fluorides can also be smoothly converted. The utility of our method is demonstrated by detoxification of harmful pesticides and hydrodebromination of a dibrominated biphenyl (analogues of flame-retardants) in gram scale., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Carboxylic acids are common moieties in medicines. They can be converted to phthalidyl esters as prodrugs. Unfortunately, phthalidyl esters are now mostly prepared in racemic forms. This is not desirable because the two enantiomers of phthalidyl esters likely have different pharmacological effects. Here we address the synthetic challenges in enantioselective modification of carboxylic acids via asymmetric acetalizations. The key reaction step involves asymmetric addition of a carboxylic acid to the catalyst-bound intermediate. This addition step enantioselectively constructs a chiral acetal unit that lead to optically enriched phthalidyl esters. A broad range of carboxylic acids react effectively under mild and transition metal-free conditions. Preliminary bioactivity studies show that the two enantiomers of chlorambucil phthalidyl esters exhibit different anti-cancer activities to inhibit the growth of Hela cells. Our catalytic strategy of asymmetric acetalizations of carboxylic acids shall benefit future development of chiral phthalidyl ester prodrugs and related molecules.

A new catalytic approach for rapid asymmetric access to spirocycles is disclosed. The reaction involves a carbene- and thiourea-cocatalyzed desymmetrization process with the simultaneous installation of a spirocyclic core. The use of a thiourea cocatalyst is critical to turn on this reaction, as no product was formed in the absence of a thiourea. Our study constitutes the first success in the carbene-catalyzed enantioselective synthesis of all-carbon spirocycles. The reaction products can be readily transformed into sophisticated multicyclic molecules and chiral ligands., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A carbene and sulfinate co-catalyzed intermolecular Rauhut-Currier reaction between enals and nitrovinyl indoles is disclosed. The carbene catalyst activates the enal and the sulfinate co-catalyst activates the nitrovinyl indole. Both activation processes are realized via the formation of covalent bonds between the catalysts and substrates to generate catalyst-bound intermediates. The dual catalytic reaction affords azepino[1,2-a]indole products with excellent stereoselectivity. Our study demonstrates the unique involvement of sulfinate as an effective nucleophilic catalyst in activating electron-deficient alkenes for asymmetric reactions. This dual catalytic approach should also encourage future explorations of both sulfinate and carbene catalysts for new reactions., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Two new steroidal alkaloids, named hookerianine A ( 1 ) and hookerianine B ( 2 ) were isolated from the stems and roots of Sarcococca hookeriana Baill., along with two known compounds, sarcorucinine G ( 3 ) and epipachysamine D ( 4 ). On the basis of spectroscopic methods and by comparison with literature data, their structures were determined. As well as X-ray crystallography was performed to confirm compound 4 . To identify novel antitumor inhibitors, all compounds were performed a CCK-8 assay against five human cancer cell lines SW480, SMMC-7721, PC3, MCF-7 and K562 in vitro. Compound 2 exhibited moderate cytotoxic activities to all cell lines with IC 50 values in the range of 5.97⁻19.44 μM. Compound 3 was the most effective one against SW480 and K562 cell lines with IC 50 values of 5.77 and 6.29 μM, respectively.

Phytochemical study of the leaves of the medicinal plant Isodon rubescens led to the isolation of three novel abietane diterpenoids, rubesanolides C-E (1-3). These diterpenes contain a unique γ-lactone subgroup formed between C-8 and C-20. Their structures were determined from analysis of spectroscopic data, and were further confirmed by X-ray crystallographic data. The compounds were evaluated for their antibacterial activity, and rubesanolide D (2) demonstrated inhibition activity against biofilm formation of the dental bacterium Streptococcus mutans.

From the medicinal plant Isodon rubescens, we isolated two novel diterpenes, rubesanolides A (1) and B (2). The compounds contain a unique β-lactone subgroup. This is the first discovery for a natural diterpene having rings A, B, and C in chair, boat, and twist-chair conformations, respectively. The structures were elucidated by analysis of spectroscopic data, and the absolute configuration of 1 was determined by X-ray diffraction.