Tupisteroide A–C,three new polyhydroxylated steroidal constituents from the roots of Tupistra chinensis

Three new steroidal compounds with polyhydroxy groups, tupisteroide A–C (1–3), were obtained from the roots of Tupistra chinensis, together with one known compound (4) that was isolated from this plant for the first time. The structures of tupisteroide A–C were determined on the basis of one‐ and two‐dimensional NMR spectroscopy, including ¹H–¹H Correlation Spectroscopy, Heteronuclear Multiple Bond Correlation, and Heteronuclear Single Quantum Coherence experiments. The isolated compounds were evaluated for their cytotoxic activities against A549, HepG2, and CaSki cancer cell lines in vitro. Among them, compounds 1, 2, and 4 did not show significant inhibitory activity, but compound 3 showed cytotoxicity against A549 cancer cell lines with IC₅₀ values of 25.0 μM. Copyright © 2012 John Wiley & Sons, Ltd.     

Six New Steroidal Saponins from Helleborus thibetanus

Six steroidal saponins, including five spirostanol glycosides, 1 – 5 , and one furostanol glycoside 1‐sulfonate, 6 , previously unknown in nature, together with three known compounds, 7 – 9 , were isolated from dried roots and rhizomes of Helleborus thibetanus. Their structures were elucidated by extensive 1D‐ and 2D‐NMR experiments, along with IR and HR‐ESI‐MS data, as well as the results of acid hydrolysis. Compounds 1 – 5 possessed a C(25)?C(27) bond and were glycosylated at HO? C(1), which was unusual in steroidal saponins.     

Pregnane‐Type Steroidal Alkaloids of Sarcococca saligna: a New Class of Cholinesterase Inhibitors

Phytochemical investigation of Sarcococca saligna by extensive bioassay‐guided fractionation resulted in the isolation of the pregnane‐type steroidal alkaloids 1 – 15 , i.e. of the five new compounds 1 – 5 and the ten known alkaloids 6 – 15 . The structures of the new alkaloids salignenamide C ( 1 ), salignenamide D ( 2 ), 2β‐hydroxyepipachysamine D ( 3 ), salignenamide E ( 4 ), and salignenamide F ( 5 ) were elucidated with the help of modern spectroscopic techniques, while the known alkaloids axillarine C ( 6 ), axillarine F ( 7 ), sarcorine ( 8 ), N³‐demethylsaracodine ( 9 ), saligcinnamide ( 10 ), salignenamide A ( 11 ), vaganine A ( 12 ), axillaridine A ( 13 ), sarsalignone ( 14 ), and sarsalignenone ( 15 ) were identified by comparing their spectral data with those reported earlier. Inhibition of electric‐eel acetylcholinesterase (EC 3.1.1.7) and horse‐serum butyrylcholinesterase (EC 3.1.1.8) by alkaloids 1 – 15 were investigated. These new cholinesterase inhibitors may act as potential leads in the discovery of clinically useful inhibitors for nervous‐system disorders, particularly by reducing memory deficiency in Alzheimer's disease patients by potentiating and effecting the cholinergic transmission process. These compounds were found to inhibit both enzymes in a concentration‐dependent fashion with the IC₅₀ values ranging from 5.21–227.92 μM against acetylcholinesterase and 2.18–38.36 μM against butyrylcholinesterase.     

Three New Eudesmanolactones (=Eudesmanolides) from Camchaya loloana

Three new eudesmanolactones (=eudesmanolides), loloanolide A ( 1 ), loloanolide B ( 2 ), and 1‐O‐acetylloloanolide B ( 3 ), together with five known compounds, were isolated from the CHCl₃ extract of the aerial parts of Camchaya loloana. Their structures were elucidated on the basis of spectroscopic analysis. This type of eudesmanolactones bearing a 2‐(hydroxymethyl)acryloyloxy group at C(8) was discovered for the first time. Compounds 1 – 3 exhibited cytotoxicity against the HepG2 cell line, with GI₅₀ values of 22.9, 18.1, and 12.8 nmol/ml, respectively.     

Total Synthesis of (−)-Batrachotoxin Enabled by a Pd/Ag-Promoted Suzuki–Miyaura Coupling Reaction

Batrachotoxin is an extremely potent cardio- and neurotoxic steroidal alkaloid found in certain species of frogs, birds, and beetles. The steroidal 6/6/6/5-membered carbocycle (ABCD-ring) is U-shaped and functionalized with two double bonds, a six-membered C3-hemiacetal across the AB-ring, a seven-membered oxazepane on the CD-ring, and a dimethylpyrrolecarboxy group at the D-ring carbon chain. These structural features present an unusual and formidable synthetic challenge. Herein we report a total synthesis of batrachotoxin based on a newly devised convergent strategy through a 22-step sequence. Enantiopure AB-ring and D-ring fragments were prepared and subjected to a crucial C(sp²)−C(sp²) coupling reaction. Although both C(sp²) centers were sterically encumbered by proximal tetrasubstituted carbon atoms, Ag₂O strongly promoted the Pd(PPh₃)₄-catalyzed Suzuki–Miyaura coupling reaction at room temperature, thereby connecting the two fragments without damaging their preexisting functionalities. Subsequent treatment with t-BuOK induced Dieckmann condensation to cyclize the C-ring. The judiciously optimized functionalizations realized oxazepane formation, carbon chain extension, and pyrrole carboxylic acid condensation to deliver batrachotoxin.     

Hybridnaturstoffe: Synthese cyclischer Hydroxamsäuren der Estra-1,3,5(10)-trien-Reihe

An approach to a new class of cyclic hydroxamic acids is described leading to a formal combination of a benzoxazine subunit related to some natural aglucones occurring in plants with the steroidal skeleton from two members of the estra-1,3,5(10)-triene series. The annelation procedure for a 4-hydroxy-1,4-oxazine moiety to the aromatic A-ring in estrone ( 1 ) and 1-hydroxy-4-methylestra-1,3,5(10)-trien-17-one ( 7 ), used as steroidal precursors, proceeds in four or three steps, respectively (Schemes 1 and 2, resp.). First, a 2-nitro group is introduced regioselectively by a novel nitrosation-oxidation procedure or by conventional nitration (→ nitrophenols 2 and 8 ). Reaction of the phenolic unit of 2 and 8 with methyl bromoacetate or ethyl chlorooxoacetate gives rise to the nitro esters 3 , 4 , 9 , and 10 , which are subjected to reductive cyclization either by means of Zn dust in ammonium chloride solution (for the acetates) or of H₂/Pt(S)/C (for the sensitive oxalates). Hence, the novel cyclic hydroxamic acids 5 , 6, 11 , and 12 of the estra-1,3,5(10)-triene series are obtained.     

Antimalarial and cytotoxic activities of pregnene-type steroidal alkaloids from Holarrhena pubescens roots

The phytochemical investigation of an alkaloidal extract of Holarrhena pubescens roots led to the isolation and identification of a new pregnene-type alkaloid, mokluangin D (1), together with nine known steroidal alkaloids (2–10). The structure of the new metabolite was determined on the basis of spectroscopic analyses including 1D- and 2D-NMR spectroscopy and mass spectrometry. Compounds 3 and 4 showed potent antimalarial activity against Plasmodium falciparum K1 stain with IC₅₀ values of 1.2 and 2.0 μM, respectively, and showed weak cytotoxic activity against the NCI-H187 cell line with IC₅₀ values of 27.7 and 30.6 μM, respectively. The substituent groups at C-3 and the carbonyl group at C-18 are important for the activity against the P. falciparum K1 stain.     

Steroidal Alkaloids from Veratrum maackii Regel with Genotoxicity on Brain‐Cell DNA in Mice

Two new steroidal alkaloids, 23‐methoxycyclopamine 3‐O‐β‐D ‐glucopyranoside ( 1 ) and isoecliptalbine ( 2 ), were isolated from the root and rhizoma of Veratrum maackii Regel , together with five known compounds, i.e., verussurine ( 3 ), verabenzoamine ( 4 ), verazine ( 5 ), isoverazine ( 6 ), and verazinine ( 7 ). Their structures were established by extensive analysis of spectroscopic data, as well as by comparison with literature data. Compounds 1 – 7 could cause DNA damage in the cerebellum and cerebral cortex of mice in a dose‐dependent manner by using single‐cell gel electrophoresis (comet assay).     

Synthesis,Characterization and Molecular Structure of a New Tetrameric Palladium(II) Complex Containing Schiff‐Bases Derived from AMTTO (AMTTO = 4‐amino‐6‐methyl‐1,2,4‐triazine‐thione‐5‐one)

The reactions of AMTTO = 4‐amino‐6‐methyl‐1,2,4‐triazine‐thione‐5‐one (AMTTO, 1 ) with 2‐hydroxybenzaldehyde (salicylaldehyde) and 4‐hydroxybenzaldehyde in methanol under reflux conditions led to the corresponding Schiff‐bases ( H₂L1 and H₂L2 ). The reaction of H₂L1 with palladium acetate in ethanol and additional recrystallization from toluene gave the tetrameric complex [Pd(L)]₄·2C₇H₈ ( 2 ). All compounds were characterized by infrared spectroscopy, elemental analyses as well as by X‐ray diffraction studies. Crystal data for H₂L1 at ?80 °C: space group P2₁/c with a = 1285.4(1), b = 707.7(1), c = 1348.2(1) pm, β = 109.32(1)°, Z = 4, R₁ = 0.0328, H₂L2 at ?80 °C: space group P4₃2₁2 with a = 762.5(1), b = 762.5(1), c = 4038.9(2) pm, Z = 8, R₁ = 0.025 and for 2 at ?103 °C: space group C2/c with a = 2862.5(6), b = 2847.6(6), c = 1727.8(4) pm, β = 105.18(3)°, Z = 8, R₁ = 0.0704.     

Ferrocenylmethylation of estrone and estradiol: Structure,electrochemistry, and antiproliferative activity of new ferrocene–steroid conjugates

Conjugates of ferrocene with steroidal estrogens as selective antiproliferative agents against hormone-dependent breast cancer cells are believed to be limited by the inherent estrogenicity of the conjugates. Motivated by a significant cytotoxicity of the ester of ferrocenecarboxylic acid and the phenolic group of estradiol toward such a cell line, we decided to explore other a -ring-tethered ferrocene–estra-1,3,5(10)-triene conjugates; in this study, ferrocenylmethylation of estradiol and estrone with (ferrocenylmethyl)trimethylammonium iodide in the presence of potassium carbonate yielded five new compounds ( 1 – 5 ). In dimethylformamide, only O-alkylated products formed ( 1 and 3 ), while a mixture of O- and C-alkylated products was obtained when methanol was used ( 2 , 4 , and 5 in addition to 1 and 3 ). All compounds were characterized using 1D and 2D NMR, IR, UV–Vis, and high-resolution mass spectrometry. Two of the conjugates, a 3-O- and a 4-C-alkylated derivative of estrone ( 3 and 4 , respectively), were also analyzed using single-crystal X-ray diffraction. A cyclic voltammetric investigation of the electrochemical properties of 1 – 5 was performed. While some of the compounds were shown to have a slight-to-moderate antiproliferative activity against at least one of the six tested human tumor cell lines and were nontoxic to (the noncancerous) fetal human fibroblasts, compound 2 (4-(ferrocenylmethyl)estra-1,3,5(10)-triene-3,17β-diol) with an IC₅₀ value of 0.34 μM was found to be more active against the hormone-dependent breast cancer cell line MCF-7 than doxorubicin. These results suggest that a -ring substitution of steroidal estrogens is a plausible strategy for preparing other ferrocene–steroid conjugates acting against tumor cells.     

Two New Cytotoxic Spirostane‐Steroidal Saponins from the Roots of Bletilla striata

Two new spirostane‐steroidal saponins, bletilnoside A ( 1 ) and bletilnoside B ( 2 ), together with five known compounds, 3 – 7 , were isolated from the roots of Bletilla striata (Thunb .) Reichb . F. The structures of the new compounds were determined based on their 1D‐ and 2D‐NMR spectral data. The isolated compounds 1 – 7 were tested for cytotoxicity against four human tumor cells (A549, SK‐OV‐3, SK‐MEL‐2, and HCT15) in vitro using a sulforhodamin B bioassay, and compounds 1, 2 , and 5 showed significant cytotoxicities against all tested tumor cell lines with IC₅₀ values ranging from 3.98±0.16 to 12.10±0.40 μM .     

Preparation via Diastereoselective Hydrogenation,Absolute Conformation and Configuration of Exogeneous Anabolic Zeranol ((3S, 7R)-3,4,5,6,7,8,9,10,11,12-Decahydro-7,14,16-trihydroxy-3-methy-1H-2-benzoxacyclotetradecin-1-one)

Hydrogenation of the ketone group in di-O-benzylderivative ( 8 ) of the known macrocyclic lactone zeralenone ( 7 ) using a novel chiral borane complex 3 . BH₃, prepared in situ, proceeded at lower temperatures with moderate diastereoselectivity (～40%, d. e. at ?60°). Unsaturated diastereomers 9 and 10 were separated, and 9 converted into zeranol ( 11 ), a known anabolic agent. Restricted conformational mobility at lower temperatures is assumed for the intermediate 8 on the basis of the temperature-dependent CD spectra of its acetyl congeners 18 and 19 . X-Ray structure analysis of 7-O-acetylderivative ( 13 ) of 11 revealed the (R)-configuration at C(7). Two crystallographically independent H₂O molecules are involved in the H-bonds, one of them (O(21)) rises the helices of the molecules of 13 along b. Small positive torsional angle [C(16)-]C(161)-C(1) [=O] (+19.3°), transoid(E) conformation of the lactone group, and nearly achiral arrangement of the C(11)-C(12) bond (torsional angle [C(11)-]C(12)-C(121)[C(161)] is ?93°) are the main conformational features that differentiate the macrocylic RAL (resorcinic-acid lactone) derivatives from the 6-membered lactone derivative 20 , studied earlier by CD. Consequently, the rules developed for the CD effects within conjugation band (around 270 nm), and n→π* band (around 255 nm) of the latter compound, cannot be applied the macrocyclic lactones.     

Separation and identification of steroidal compounds with cytotoxic activity against human gastric cancer cell lines <Emphasis Type="Italic">in vitro</Emphasis> from the rhizomes of <Emphasis Type="Italic">Paris polyphylla</Emphasis> var. <Emphasis Type="Italic">chinensis</Emphasis>

A novel steroidal saponin, along with 12 known steroidal compounds, was isolated from the rhizomes of Paris polyphylla var. chinensis. Spectral data, including two-dimensional NMR, showed that the structure of the novel saponin was 3β,21-dihydroxypregnane-5-en-20S-(22,16)-lactone-1-O-α-L-rhamnopyranosyl(1→2)-[β-D-xylopyranosyl(1→3)]-β-D-glucopyranoside. The isolated steroidal compounds were evaluated for their cytotoxic activity on human gastric cancer cell line HepG₂, SGC7901, BxPC3. Diosgenin-3-O-α-L-rhamnopyranosyl(1→2)[α-L-rabinofuranosyl(1→4)]-β-D-glucopyranoside exhibited the most potent cytotoxic activity among the isolated steroids. Published in Khimiya Prirodnykh Soedinenii, No. 6, pp. 556–560, November–December, 2007.     

Synthesis,Characterization, and Crystal Structure of the New Schiff‐Bases derived from 1,2,4‐Triazole and the Structure of [(PPh3)2Cu(AMTT)]NO3·EtOH (AMTT = 4‐Amino‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione)

The reactions of 4‐amino‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione (AMTT, L1 ) with 2‐thiophen carbaldehyde, salicylaldehyde and 2‐nitrobenzaldehyde in methanol led to the corresponding Schiff‐bases ( L1a‐c ). The reaction of L1 with [(PPh₃)₂Cu]NO₃ in ethanol gave the ionic complex [(PPh₃)₂Cu(L1)]NO₃·EtOH ( 2 ) All compounds were characterized by infrared spectroscopy, elemental analyses as well as by X‐ray diffraction studies. Crystal data for L1a at 20 °C: space group P2₁/n with a = 439.6(2), b = 2074.0(9), c = 1112.8(4) pm, β = 93.51(3)°, Z = 4, R₁ = 0.0406, L1b at ?80 °C: space group P2₁/n with a = 1268.9(2), b = 739.3(1), c = 1272.5(1) pm, β = 117.97(1)°, Z = 4, R₁ = 0.0361, L1c at ?80 °C: space group P2₁/n with a = 847.8(1), b = 1502.9(2), c = 981.5(2) pm, β = 110.34(1)°, Z = 4, R₁ = 0.0376 and for 2 at ?80 °C: space group with a = 1247.8(1), b = 1270.3(1), c = 1387.5(1) pm, α = 84.32(1)°, β = 84.71(1)°, γ = 63.12(1)°, Z = 2, R₁ = 0.0539.     

A new antiviral pregnane from a gorgonian-derived Cladosporium sp. fungus

A new pregnane, 3α-hydroxy-7-ene-6,20-dione (1), and five known steroids (2–6), along with one known steroidal glycoside (7) were obtained from the fungus Cladosporium sp. WZ-2008-0042 cultured from a gorgonian Dichotella gemmacea collected from the South China Sea. The structure and absolute configuration of the new compound (1) were elucidated by comprehensive spectroscopic data and X-ray diffraction data. The compound has a rare configuration of 3α-OH that is different from most of pregnanes. All of the isolated compounds were evaluated for their antiviral activities against respiratory syncytial virus (RSV). Among them, 1 exhibited potential antiviral activity with the IC₅₀ value of 0.12 mM.     

Long-Wavelength-Absorbing and -Emitting Carbostyrils with High Fluorescence Quantum Yields

Synthesis, absorption and fluorescence spectra, as well as quantum yields of a series of donor-acceptor-substituted carbostyrils (=quinolin-2(1H)-ones), are reported. Unprecedented strong absorption maxima (ε=10000 – 20000) close to the visible spectrum, large Stokes shifts up to 130 nm, and quantum yields up to 0.7 are obtained with derivatives containing donor substituents at C(6) and C(7), and either one Ph substituent at C(3) or one CF₃ residue at C(4). For analytical applications in biochemistry and medicine, N(1)-functionalization, or amidoacylation at C(3) in the case of the CF₃ derivatives, is possible without a concomitant hypsochromic shift of their absorption and emission maxima. Semiempirical molecular-orbital calculations (AM1 for structures, ZINDO for electronic transition energies) prove to be a suitable tool for the prediction of absorption properties of these compounds. The crystal-structure analysis of 6,7-dimethoxy-1-methyl-3-nitro-4-(trifluoromethyl)quinolin-2-(1H)-one ( 7 ) (C₁₃H₁₁F₃N₂O₅, monoclinic, P2₁/c, a=12.372(2), b=12.154(2), c=10.119(2)Å, β=112.95(2)°) shows that the NO₂ group, squeezed between the CF₃ and the C=O group, is oriented almost perpendicularly (87.8(4)°) to the ring plane. The intramolecular F⋅⋅⋅N distance between the CF₃ and the NO₂ group is only 2.513(4)Å.     

Synthesis of Substituted Pyrrolo[3,4‐a]carbazoles

The cycloaddition between N‐protected 3‐{1‐[(trimethylsilyl)oxy]ethenyl}‐1H‐indoles and substituted maleimides (= 1H‐pyrrole‐2,5‐diones) yielded substituted pyrrolo[3,4‐a]carbazole derivatives bearing an additional succinimide (= pyrrolidine‐2,5‐dione) moiety either at C(5a) or C(10b) depending on the type of the protection group at the indole N‐atom. Derivatives substituted at C(10b) were isolated when the protection group, Me₃Si or Boc (^tBuOCO), was eliminated during the reaction (Schemes 2 and 3), whereas a substitution at C(5a) was observed when an electron‐withdrawing group, Tos (4‐MeC₆H₄SO₂) or pivaloyl (Me₃CCO), was not eliminated (Scheme 1). Complex results were found in reactions between 1‐(trimethylsilyl)‐3‐{1‐[(trimethylsilyl)oxy]ethenyl}‐1H‐indole, in contrast to formerly reported results (Scheme 3). Some derivatives of 1H,5H‐[1,2,4]triazolo[1′,2 : 1,2]pyridazino[3,4‐b]indole‐1,3(2H)‐dione were obtained from reactions with 4‐phenyl‐3H‐1,2,4‐triazole‐3,5(4H)‐dione (Scheme 2). All structures were established by spectroscopic data, by calculations, and one representative structure was confirmed by an X‐ray crystallographic analysis (Fig.). Finally, the formation of the different structure types was discussed, and compared with similar reactions reported in the literature.     

Structure elucidation and complete NMR spectral assignments of glucosylated saponins of cantalasaponin I

Five new glucosylated steroidal glycosides, cantalasaponin I‐B₁ (1), I‐B₂ (2), I‐B₃ (3), I‐B₄ (4) and I‐B₅ (5), were isolated and purified from the transformed product of the cantalasaponin I by using Toruzyme 3.0 l as biocatalyst. Their structures were elucidated on the basis of high‐resolution electrospray ionization mass spectrometry, one‐dimensional (¹H and ¹³C NMR) and two‐dimensional [COSY, heteronuclear single‐quantum correlation (HSQC), HMBC and HSQC‐TOCSY] NMR spectral analyses and chemical evidence. Copyright © 2012 John Wiley & Sons, Ltd.     

Three New C19‐Diterpenoid Alkaloids from Aconitum transsectum

Three new C₁₉‐diterpenoid alkaloids, named aconitramines A ( 1 ), B ( 2 ), and C ( 3 ), were isolated from Aconitum transsectum. By UV, IR, 1D‐ and 2D‐NMR, and MS analyses, their structures were elucidated as 18‐methoxyvilmoraconitine, 18‐demethoxydolichotine A, and 18‐demethoxydolichotine B. Compound 1 is the second known C₁₉‐diterpenoid alkaloid with a three‐membered ring formed by C(8), C(9), and C(10).     

Krempenes A–D: A Series of Unprecedented Pregnane‐Type Steroids from the Marine Soft Coral Cladiella krempfi

Four new pregnane‐type steroids, krempenes A–D ( 1 – 4 ), were isolated from the marine soft coral Cladiella krempfi. Their structures were elucidated on the basis of 1D‐ and 2D‐NMR analyses, as well as MS experiments. Krempene A ( 1 ) contains a very unusual structural motif, with a hexacyclic oxadithiino unit fused to the steroidal ring A. Krempene B ( 2 ) is a 19‐norpregnane steroid, the 19‐Me group formally being transferred to position 4. Furthermore, krempene D contains an unusual C?C bond at C(7) of the pregnane skeleton.