Sesquiterpene lactone dimers from the fruit of Carpesium abrotanoides L.

Seven undescribed sesquiterpene lactone dimers (SLDs) (carpeabrodilactones A-G), one known SLD, and six known sesquiterpenes were isolated from the fruit of Carpesium abrotanoides L. Carpeabrodilactone A was a dimeric carabrane featuring a rare C-13-C-13' linkage. Carpeabrodilactones B and C are the first two SLDs to be described possessing a carabranolide unit and a guaianolide unit connected by an O-ether linkage.

New protein tyrosine phosphatase inhibitors from fungus F07ZB1707.

Twelve new compounds, aspergorakhins A-L (1-12) coupled with one known xanthone leptosphaerin D (13), were isolated from the extract of soil-derived fungus F07ZB1707. Their structures were elucidated by spectroscopic data analysis including UV, IR, NMR, and HRESIMS. The absolute configurations of 5 and 8-11 were identified using ECD and OR calculations.

Xylomexicanins K-N: limonoids from the leaves and twigs of .

Six new compounds, xylomexicanins K-N (-), granasteroid () and 5-methoxy-2-pentylbenzofuran-7-ol (), along with nine known compounds were isolated from the leaves and twigs of . Among them, was a biogenetic precursor of 1,8,9-phragmalin limonoid, and represent the first example of degraded A-ring limonoid. The structures of them were elucidated on the basis of one- and two-dimensional NMR spectroscopic data (including H, C-NMR, DEPT, H-H COSY, HSQC, HMBC, and NOESY) and confirmed by high-resolution mass spectrometry.

Directed and Metalation of Naphthalene 1,8-Diamide: Complementing SAr Reactivity for the Synthesis of Substituted Naphthalenes.

Mono- and dianion species of 1,8-naphthalene diamide were generated under -BuLi/TMEDA conditions and trapped with a variety of electrophiles to give 2- and 2,7- substituted products and . Using Suzuki-Miyaura cross-coupling, mono- and di-iodinated products were converted into the corresponding 2-aryl () and 2,7-diaryl () products, respectively. The amide-amide rotation barrier of was established by VT NMR, and the structure of fluorenone structure , obtained by metalation, was secured.

Multistep Photoisomerization of Dimesitylboron-Functionalized Stilbene Analogues.

Dimesitylboron-functionalized stilbene derivatives have been found to undergo an unusual regioselective photoisomerization upon irradiation at 365 nm. Using NMR to follow the photoreaction, the structures of key reaction intermediates and the final products were established. This photoisomerization occurs in four steps: isomerization, Diels-Alder reaction, di-π-methane rearrangement, and ring opening with [1,3]-H migration.

Structural Dynamics and Stereoselectivity of Chiral Benzylideneamine N,C-Chelate Borane Photo-Thermal Isomerization.

New chiral N,C-chelate organoboron compounds based on benzylideneamines (bza) with the general formula of B(bza-R)Mes (R=H or Me; Mes=mesityl) are reported. A chiral substituent group R- or S-CH(CH )Ph (Ph=phenyl) was introduced to the imine center, which imposed a previously unobserved pseudo- or axial-chirality on the BMes , creating distinct diastereomers. NMR spectroscopic studies established that the diastereomers undergo slow exchange in solution at ambient temperature.

Isolation and characterization of tambjamine MYP1, a macrocyclic tambjamine analogue from marine bacterium .

Tambjamines are natural products that consist of a conserved bipyrrole core functionalized with different imines giving rise to many derivatives. The core structure of tambjamines allows ion coordination through the nitrogen atoms, which is a key aspect in many of their observed antimicrobial, anticancer, and antimalarial bioactivities. Minor variances in the compound structure have a considerable impact on the potency of these activities, so identifying new analogues is valuable for maximizing tambjamine biological potential.

Stabilising fleeting intermediates of stilbene photocyclization with amino-borane functionalisation: the rare isolation of persistent dihydrophenanthrenes and their [1,5] H-shift isomers.

The key intermediate, 4a,4b-dihydrophenanthrene (DPH), involved in the photocyclization of stilbene and derivatives is known to be unstable, and is therefore poorly characterized/understood. We have found that functionalising stilbenes with NMe and BMes groups can greatly enhance the stability of 4a,4b-DPHs, allowing quantitative isolation and full characterization of these rare species. Furthermore, we discovered that the new amino-borane decorated 4a,4b-DPHs can undergo thermal [1,5] H sigmatropic shift, forming isomers 4a,10a-DPHs.

Triaryl-Boron Functionalized Dinuclear Platinum Complexes Linked by Photoisomerizable Bpe Ligand: Luminescence and Isomerism.

We report herein a series of triarylboron-functionalized Pt(II) dinuclear complexes using a photoactive bis(4-pyridyl)ethylene (bpe) bridging unit. The new Pt(II) complexes display phosphorescence at both room temperature and 77 K. Depending on the conditions under which crystals of the complexes were grown, either the cis- or trans-isomers could be obtained.

Xylomexicanins I and J: Limonoids with Unusual B/C Rings from Xylocarpus granatum.

Two tetranortriterpenoids with new skeletons, xylomexicanins I and J (1 and 2), were isolated during the investigation of chemical constituents from seeds of the Chinese mangrove, Xylocarpus granatum. Xylomexicanin I (1) is an unprecedented limonoid with bridged B- and C-rings. A biosynthesis pathway for 1 from xylomexicanin F is proposed.

Atropisomerism in Tertiary Biaryl 2-Amides: A Study of Ar-CO and Ar-Ar' Rotational Barriers.

A rotational barrier study was performed on eight tertiary biaryl 2-amides using variable-temperature (VT) NMR and exchange (EXSY) spectroscopy experiments. Seven out of the eight 2-amido-2'-methylbiphenyls with additional 3- and 6-substitution patterns (1-7) were found to have approximately similar rotational barriers (ΔG = 56.5-67.

Unusual Fragmentation and Transformation of an N-Heterocyclic Carbene by a Stable Phosphonium-Borane peri-Functionalized Naphthalene.

A 1-phosphonium-8-borane-decorated naphthalene molecule 2 has been found to react with N,N'-dimethylimidazol-2-ylidene (IMe), a popular member of the N-heterocyclic carbene (NHC) family, which converts it into two vinyl-amine fragments one of which is trapped between the phosphonium and borane unit by the formation of a C-C and a B-N bond. The same reactivity was not observed for larger NHC molecules. Control experiments and mechanistic studies have established the involvement of an ylide-borane molecule and an imidazolium salt in addition to IMe carbene in this new transformation of an NHC.

Chemical Constituents of Plants from the Genus Eupatorium (1904-2014).

Eupatorium (family: Compositae), which comprises nearly 1200 species, is distributed throughout tropical America, Europe, Africa, and Asia. Up to now, the reported constituents from the genus Eupatorium involve flavonoids, terpenoids, pyrrolizidine alkaloids, phenylpropanoids, quinonoids, essential oils, and some others, altogether more than 300 compounds. Studies have shown that Eupatorium and its active principles possess a wide range of pharmacological activities, such as cytotoxic, antifungal, insecticidal, antibacterial, anti-inflammatory, and antinociceptive activities.

A new eudesmane sesquiterpene from Dichrocephala integrifolia.

A new sesquiterpene, eudesm-11-ene-4alpha,7beta,9beta-triol, was isolated from the EtOH extract of aerial parts of Dichrocephala integrifolia. Its structure was determined on the basis of spectral analysis of 1D and 2D NMR data.

Formation of azaborines by photoelimination of B,N-heterocyclic compounds.

Highly fluorescent π-conjugated polycyclic azaborines can be prepared from B,N-heterocyclic compounds with a BR2 -CH2 unit through the elimination of an R-H molecule (see scheme). These clean photoelimination reactions occur both in solution and in polymers doped with the precursors.

Xylomexicanins C and D, new mexicanolide-type limonoids from Xylocarpus granatum.

Two new limonoids, named xylomexicanins C and D, were isolated from a dichloromethane extract of the seeds of Xylocarpus granatum cultivated in Hainan, China, and their structures were elucidated on the basis of one- and two-dimensional NMR (including 1H, 13C-NMR, DEPT, 1H-1H COSY, HSQC, HMBC, and NOESY) and confirmed by high-resolution mass spectrometry. Xylomexicanin C exhibited antiproliferative activity against human breast carcinoma cells (KT).

PPARγ agonist from Chromolaena odorata.

A phytochemical investigation of Chromolaena odorata resulted in the isolation of five new compounds, 5aα,6,9,9aβ,10-pentahydro-10β-hydroxy-7-methylanthra[1,2-d][1,3]dioxol-5-one (1), 1,2-methylenedioxy-6-methylanthraquinone (2), 3-hydroxy-1,2,4-trimethoxy-6-methylanthraquinone (3), 3-hydroxy-1,2-dimethoxy-6-methylanthraquinone (4), and 7-methoxy-7-epi-medioresinol (5), together with 12 known compounds, odoratin (6), 3β-acetyloleanolic acid (7), ursolic acid (8), ombuin (9), 4,2'-dihydroxy-4',5',6'-trimethoxychalcone (10), (-)-pinoresinol (11), austrocortinin (12), tianshic acid (13), cleomiscosin D (14), (-)-medioresinol (15), (-)-syringaresinol (16), and cleomiscosin A (17). All the compounds were evaluated for their PPARγ transactivation activity, and compound 6 showed moderate activity with an EC(50) value of 3.10 μM.

Antiandrogenic, maspin induction, and antiprostate cancer activities of tanshinone IIA and its novel derivatives with modification in ring A.

Expression of metastatic suppressor maspin is lost in advanced prostate cancer. Clinically relevant mutations in androgen receptor (AR) convert antiandrogens into AR agonists, promoting prostate tumor growth. We discovered tanshinone IIA (TS-IIA) is a potent antagonist of mutated ARs and induces maspin expression through AR.

Novel taxa-4(20),12-diene and 2(3→20)abeotaxane from needles of Taxus canadensis.

A novel 6/8/6-membered taxane with a rare C-12(13)-double bond and rare 2(3→20)abeotaxane were isolated from the needles of Taxus canadensis. Their structures were characterized as 7β,9α,10β-triacetoxytaxa-4(20),12-diene-2α,5α,11β-triol (1) and 2α,7β,10β-triacetoxy-5α-hydroxy-2(3→20)abeotaxa-4(20),11-diene-9,13-dione (2) on the basis of 1D and 2D spectroscopic data. 1 is the first example of a natural taxane without substitution at both C-13 and C-14.

Achillinin A, a cytotoxic guaianolide from the flower of Yarrow, Achillea millefolium.

Achillinin A (2β,3β-epoxy-1α,4β,10α-trihydroxyguai-11(13)-en-12,6α-olide, 1), a new guaianolide isolated from the flower of Achillea millefolium, exhibited potential antiproliferative activity to A549, RERF-LC-kj and QG-90 cells with 50% inhibitory concentration (IC(50)) values of 5.8, 10 and 0.31 µM, respectively.

A novel taxane 13-glucoside and other taxanes from the leaves of Taxus cuspidata.

Three new taxanes, 2 α,9 α,10 β-triacetoxy-13 α-( β-D-glucopyranosyloxy)taxa-4(20),11-dien-5 α-ol, 5 α,10 β,13 α-triacetoxytax-11-ene-2 α,7 β,9 α,20-tetraol, and 5 α,10 β,13 β-triacetoxy-2 α,7 β-dihydroxy-2(3→20) abeotaxa-4(20),11-dien-9-one, were isolated from the leaves of the Japanese yew, Taxus cuspidata. Compound 1 is the first example of a taxane with 13-glycosidic linkage.

Remarkable reactions and intermediates in titanocene(IV) chemistry: migratory insertion reactions of 2,2-disubstituted-1-alkenes, intramolecular 1,5-σ bond metathesis via ε-agostic interactions, and a rare example of a β-agostic alkyltitanocene complex.

The compound Cp(2)TiMe(2) reacts with [Ph(3)C][B(C(6)F(5))(4)] in CD(2)Cl(2) at 205 K to give, inter alia, [Cp(2)TiMe(CD(2)Cl(2))][B(C(6)F(5))(4)]. This solvent-separated ion pair reacts in turn with 2,4-dimethyl-1-pentene (DMP) to give a series of cationic species, the first being the alkene complex [Cp(2)TiMe(DMP)](+), which undergoes ready migratory insertion to form the σ-alkyl complex [Cp(2)Ti(CH(2)CMe(2)CH(2)CHMe(2))](+). The latter, which does not contain a β-hydrogen atom, rearranges rapidly via an unprecedented 1,5-σ bond metathesis reaction involving two isomeric ε-agostic species to give the σ-alkyl species [Cp(2)Ti(CH(2)CHMeCH(2)CMe(3))](+); this does contain a β-hydrogen atom and, in concurrent processes, eliminates H(2) or 2,4,4-trimethyl-1-pentene (a major product) to form respectively the allylic complex [Cp(2)Ti{η(3)-(CH(2))(2)CCH(2)CMe(3)}](+) (a major product) or the hydride complex [Cp(2)TiH](+).

A new taxane with an opened oxetane ring from the needles of Taxus cuspidata.

A new taxoid metabolite was isolated from the MeOH extract of Taxus cuspidata needles. The structure was established as (2alpha,5alpha,7beta,9alpha,10beta,13alpha)-10,13,20-tris(acetyloxy)-1,4,5,7,9-pentahydroxytax-11-en-2-yl benzoate on the basis of spectral analyses including 1H- and 13C-NMR, HMQC, HMBC, and NOESY, and confirmed by HR-FAB-MS.

Design and synthesis of androgen receptor antagonists with bulky side chains for overcoming antiandrogen resistance.

Incorporation of curcumin and beta-ionone into one chemical entity led to identification of a novel antiandrogen with two bulky side chains, 6, which is a pure antagonist of the wild-type and the T877A, W741C, and H874Y mutated androgen receptors (AR), showing no cross-reactivity with progesterone receptor and low micromolar cytotoxicity in LNCaP, PCa-2b, 22Rv1, and C4-2B prostate cancer cells. Molecular modeling indicates 6 adopts a "Y"-shape conformation and forms multiple hydrogen bonds with AR backbone.

Structures and properties of nonchelated, d0 alkyl alkene complexes of the type [Cp2ZrMe(alkene)]+: elusive intermediates during Ziegler-Natta polymerizations of alkenes.

Caught in the act: An alkyl alkene Zr(IV) complex (see picture; Cp = C(5)H(5)) has been synthesized and characterized for the first time. The alkene bonding mode is highly asymmetric, and C2 is quite carbocationic. There is also evidence for rotation about the C1-C2 bond.