Mufolinin A,an unprecedented ring A-seco 10-ethyllimonoid from Munronia unifoliolata

Mufolinin A(1), a ring A-seco rearranged limonoid with an unprecedented ethyl at C-10 and novel 6/6/6/5 fused-ring skeleton, together with three new potential precursors(ring A-seco limonoids, 2–4) were isolated from Munronia unifoliolata. Their structures and absolute configurations were confirmed by nuclear magnetic resonance(NMR), high resolution electrospray ionization mass spectroscopy(HRESIMS), X-ray crystallography, electronic circular dichroism(ECD) calculations and NMR calculations with...     

Eight new limonoids from Turraea pubescens

Eight new ring B-seco limonoids, turrapubesic acids A-C (1-3) and turrapubesins C-G (4-8), along with turraflorin E and isoazadironolide were isolated from the twigs and leaves of Turraea pubescens. Turrapubesic acids A-C (1-3) are a group of ring B-seco limonoid 17-carboxylic acids with a new C₂₃ skeleton, and turrapubesin C (4) incorporates an unprecedented 1,30-oxygen bridge. The structures including absolute stereochemistry of 1-8 were established on the basis of extensive NMR spectroscopic analysis and CD study. The cytotoxicity of the isolates against the P-388 and A-549 cells was evaluated.     

Synthesis of Novel <Emphasis Type="Italic">D</Emphasis>-<Emphasis Type="Italic">Seco</Emphasis>-Pregnenes

Summary. A new synthetic route was developed for the preparation of trans-3-hydroxy-16,17-seco-pregna-5,17(20)-dien-16-al, using Grob fragmentation as the key step. This seco-steroid contains a formyl group and an unsaturated side-chain in a sterically favourable position, and is therefore a promising starting material for the synthesis of novel condensed steroid heterocycles.Received March 22, 2003; accepted April 22, 2003 Published online September 25, 2003     

Nuclear Spin‐Noise Spectra of Hyperpolarized Systems

Spin‐noise appeal : Detection of NMR spin‐noise is very appealing when dilute hyperpolarized species are considered. Continuous monitoring of the noise absorption at the Larmor frequency enables determination of T₁ and T₂*, independently of the static magnetic field. An inductively coupled microcoil located inside the NMR tube (see picture) allows acquisition of ¹²⁹Xe spin‐noise spectra without radio‐frequency excitation.

     

Aphanalides A–H,ring A-seco limonoids from the fruits of Aphanamixis polystachya

Eight new ring A-seco limonoids, aphanalides A–H (1–8) were isolated from the fruits of Aphanamixis polystachya. Aphanalides A–C (1–3) are the first examples of ring A-seco limonoids with an unusual oxetane ring between C-7 and C-14. The structures of aphanalide A (1) and aphanalide C (3) were confirmed by single-crystal X-ray studies. Their structures including absolute stereochemistry were established on the basis of extensive NMR spectroscopic analysis, by comparison of experimental and calculated electron circular dichroism (ECD) and by X-ray diffraction, representing the first report of assignment of absolute configuration of such type ring A-seco limonoids. The biogenetic origin of aphanalides A–D (1–4) from aphanalides E–H (5–8) was also postulated.     

Synthesis,structure and investigations of tuberculosis inhibition activities of new 4‐methyl‐1‐substituted‐1H‐1,2,4‐triazole‐5(4H)‐thione

By the reaction aminomethylation, chloromethylation and acylation of 4‐methyl‐4H‐1,2,4‐triazole‐3‐thiol, 4‐methyl‐1‐substituted‐1H‐1,2,4‐triazole‐5(4H)‐thione 1‐8 were obtained. Molecular structure of the obtained compounds was confirmed by an elemental analysis, IR, ¹H NMR and ¹³C NMR spectra and additionally by X‐ray analysis for 2. Six new compounds 1,2,4‐7 were tested for antibacterial activity against Mycobacterium smegmatis, Mycobacterium phlei and avirulent strain Mycobacterium H₃₇Ra.     

Conformations of the 10-membered Ring in 5, 10-Secosteroids. II. (E)-3α-Acetoxy-5, 10-seco-1 (10)-cholesten-5-one and (E)-5, 10-seco-1 (10)-cholestene-3, 5-dione

(E)-3α-Acetoxy-5, 10-seco-1(10)-cholesten-5-one ( 3 ) was synthesized by fragmentation of 3α-acetoxy-5α-cholestan-5-ol ( 1 ) using the photochemical version [3] of the lead tetraacetate reaction [4], and transformed into the corresponding 3-oxo-compound ( 5 ). Two conformations ( A and B ) were deduced for the 10-membered ring of 3 by analysis of the ¹H- and ¹³C-NMR. spectra in toluene. The major conformation ( A ) corresponds to that found in the solid state by X-ray analysis. According to its NMR. spectra in toluene, the medium-sized ring of the diketone 5 exists also predominantly in two conformations, the major one being analogous to A (the solid-state conformation of the 3β-acetoxy isomer ( 9 ) [1]) and the minor one to A (see above). The stereochemistry of the acidcatalyzed and thermal cyclisations of 3 as well as of the corresponding 5-oxime is discussed in terms of conformational factors.     

Molecular electrostatic potentials and electron densities in azatriprismanes and nitroazatriprismanes

Triprismane, a C₆H₆ isomer of benzene, belongs to a class of strained hydrocarbons. In this work, the energy and charge distributions in a series of aza (C₆NH_6–) and nitroaza (CNO₂)_6–N, (with =1...6) derivatives of triprismane have been analyzed using the ab initio Hartree–Fock (HF)-derived molecular electrostatic potentials and molecular electron densities. Electrostatic potential investigations have shown that the electron-rich regions around nitrogen along a series of azatriprismanes and those near oxygens of nitro group in nitroazatriprismanes become smaller on encompassing from the hexanitroaza to nitroazatriprismane. As revealed from the molecular electrostatic potential (MESP) topography for the series of azatriprismanes the MESP minimum near nitrogen become shallow with increasing nitrogen content. Heats of formation obtained from the isodesmic reaction approach in the C₆N₆H_6– and (CNO₂)_6–N series correlate well with the electron density at the bond-critical point of the X— N (X = C or N) bonds of the triprismane framework.SPG is grateful to the Council of Scientific and Industrial Research (CSIR project 01(1772)/02/EMR-II), New Delhi, India. KAJ thanks CSIR for the Junior Research Fellowship. Thanks are due to C-DAC, Pune, for providing computational facilities.     

Synthesis and NMR analysis of 2,4-dichloro-1-pentene and of 2,4-dichloro-1-pentene-1-d1

The compound 2,4-dichloro-1-pentene-1-d₁ ( 1 ) was synthesized starting from and CH?CNa. In the last stage of the synthesis on activated carbon-HgCl₂ catalyst), ( 3 ) were formed together with ( 1 ). The NMR parameters of ( 1 ), its cis and trans isomers and ( 2 ) were obtained in C₆D₆ solution at 100 MHz. Theoretical spectra of ( 1 ) at 60 MHz were simulated with the aid of a computer, using as input the NMR parameters obtained at 100 MHz and good agreement with the experiment was obtained.     

Hydrogen Bonding in Aprotic Solvents,a New Strategy for Gelation of Bioinspired Catecholic Copolymers with N‐Isopropylamide

Copolymers of N‐isopropylacrylamide (NIPAM) and dopamine methacrylate can establish a reversible, self‐healing 3D network in aprotic solvents based on hydrogen bonding. The reactivity and hydrogen bonding formation of catechol groups in copolymer chains are studied by UV–vis and ¹H NMR spectroscopy, while reversibility from sol to gel and inverse as well as self‐healing properties are tested rheologically. The produced reversible organogel can self‐encapsulate physically interacting or chemically bonded solutes such as drugs due to thermosensitivity of the used copolymer. This system offers dual‐targeted and controlled drug delivery and release—by slowing down release kinetics by supramolecular bonding of the drug and by reducing diffusion rates due to modulus increase.

     

Ambient Temperature Ligation of Diene Functional Polymer and Peptide Strands onto Cellulose via Photochemical and Thermal Protocols

In the present contribution, two novel ambient temperature avenues are introduced to functionalize solid cellulose substrates in a modular fashion with synthetic polymer strands (poly(trifluoro ethyl methacrylate), PTFEMA, M_n = 4400 g mol⁻¹, Đ = 1.18) and an Arg‐Gly‐Asp (RGD) containing peptide sequence. Both protocols rely on a hetero Diels–Alder reaction between an activated thiocarbonyl functionality and a diene species. In the first—thermally activated—protocol, the cellulose features surface‐expressed thiocarbonylthio compounds, which readily react with diene terminal macromolecules at ambient temperature. In the second protocol, the reactive ene species are photochemically generated based on a phenacyl sulfide‐decorated cellulose surface, which upon irradiation expresses highly reactive thioaldehyde species. The generated functional hybrid surfaces are characterized in‐depth via ToF‐SIMS and XPS analysis, revealing the successful covalent attachment of the grafted materials, including the spatially resolved patterning of both synthetic polymers and peptide strands using the photochemical protocol. The study thus provides a versatile platform technology for solid cellulose substrate modification via efficient thermal and photochemical ligation strategies.

     

Design,synthesis and biological evaluation of novel 6,7,8,9‐tetrahydro‐2‐(2‐aryloxypyrimidin‐4‐yl)‐2H‐[1,2,4]triazolo[4,3‐a]azepin‐3(5H)‐ones

A series of novel 6,7,8,9‐tetrahydro‐2‐(2‐aryloxypyrimidin‐4‐yl)‐2H‐[1,2,4]triazolo[4,3‐a]azepin‐3(5H)‐ones were designed and efficiently synthesized. Their structures were determined by IR, ¹³C and ¹H NMR, mass spectroscopy, and elemental analysis. These compounds were screened for herbicidal activities against rape and barnyard grass. Compounds 5a‐5f and 5m exhibited moderate herbicidal activity against rape. In addition, the synthesis of the intermediate 1‐(azepan‐2‐ylidene)‐2‐(2‐chloropyrimidin‐4‐yl)‐hydrazine ( 3 ) was studied and the reason for the low yield in the initial procedure is discussed as well.     

Ceramicine A and walsogyne A, novel limonoids from two species of Meliaceae

Two novel limonoids, ceramicine A (1) without any methyls at C-4, and walsogyne A (2) with a ring C-seco limonoid, have been isolated from the barks of Chisocheton ceramicus and Walsura chrysogyne, respectively, and the structures were fully elucidated on the basis of spectroscopic data. Ceramicine A (1) and walsogyne A (2) showed a moderate cytotoxic activity.     

Proton exchange and protonation of substituted oxadiazoles in trifluoroacetic acid

The rates of NH? COOH proton exchange between 5-amino-( 1a ) and 5-N-methylamino-( 1b )3-[2-(5′-nitro-2′-furyl)vinyl]-1,2,4-oxadiazoles and trifluoroacetic acid (TFA) have been measured by NMR spectroscopy. The values of the first-order rate constant and thermodynamic parameters for 1a and 1b , respectively, are: k_app (sec^?1) = 820 and 40 (50°C), ΔF (kcal/mole) = 14·7 and 16·5, ΔH^# (kcal/mole) = 17·3 and 24·3 and ΔS^# (e.u.) = 17 and 34. The comparison of rate constants indicates that after correction for proton equivalency proton exchange in 1a is faster than in 1b by a factor of ten. The presence of an NH₂ proton resonance ( 1a ) and an N-methyl doublet (J = 5·0 Hz) between 0 and 30° ( 1b ) suggests that 1a and 1b are present as amines and not as imines in TFA.     

Weak and strong hydrogen‐bonding patterns in the structure of 2,4‐bis(2‐­hydroxy­benzoyl)‐2,3‐di­hydro‐1H‐pyrido­[2,1‐b][1,3]­benzo­thia­zole

The title compound, C₂₅H₁₉NO₄S, (IV), was produced by a cyclo­condensation reaction similar to that which had previously produced an unexpected product, thus giving a novel route for such reactions. The structure of (IV) contains two S(6) motifs formed by strong intramolecular O—H?O hydrogen bonds. Weak C—H?O hydrogen bonds form primary C(11), R(7) and R(8) motifs which combine to form a complex three‐dimensional network.     

Novel Highly Active Niobium Catalysts for Ring Opening Metathesis Polymerization of Norbornene

Ring‐opening metathesis polymerization (ROMP) of norbornene catalyzed by niobium(V) N,N‐dialkylcarbamates Nb(O₂CNR₂)₅, R = Et ( 1 ), Me ( 2 ) was studied in the presence of methylaluminoxane (MAO) as a cocatalyst. These novel catalytic systems resulted very active in chlorobenzene: 1 in the presence of methylaluminoxane catalyzes the ROMP of norbornene with the highest activity (29 000 kg of polymer/mol of catalyst × hour) never reported up to now for niobium catalysts. The high productivity appears particularly attractive considering that these precursors are rather cheap and easy to synthesize and to handle. Polynorbornenes were characterized by FT‐IR and NMR spectroscopies and by DSC calorimetry. A new FT‐IR method for the swift determination of the cis/trans content of the polymer is presented.

     

Triorganophosphine–dithiomonometaphosphoryl halides

The title compounds, ethyldiphenylphosphine–dithiomono­metaphosphoryl chloride, EtPh₂PPS₂Cl, C₁₄H₁₅ClP₂S₂, (I), and tris‐n‐propyl­phosphine–di­thio­monometa­phospho­ryl chloride and bromide, ⁿPr₃PPS₂Cl, C₉H₂₁ClP₂S₂, (II), and ⁿPr₃PPS₂Br, C₉H₂₁BrP₂S₂, (III), respectively, are the first phosphine‐stabilized di­thio­monometa­phospho­ryl halides to be structurally characterized. In the tris‐n‐propyl­phosphine derivatives, the central PP donor–acceptor bond becomes longer in the order bromo < chloro < fluoro. Substitution of the tris‐n‐propyl­phosphine group in (II) by the more bulky ethyl­di­phenyl­phosphine group also leads to a longer PP bond. These structural features agree with the observed ³¹P NMR data. In (II) and (III), the central P—P bond coincides with the crystallographic threefold axis, entailing site‐occupational disorder for the S₂Y group.     

A series of 1‐[2‐aryl‐1‐diazenyl]‐3‐({3‐[2‐aryl‐1‐diazenyl]perhydrobenzo[d]imidazol‐1‐yl}methyl)perhydrobenzo[d]imidazoles. Synthesis and characterization

Reaction of diazonium salts with solutions of 1,2‐diaminocyclohexane mixed with formaldehyde affords the 1‐[2‐aryl‐1‐diazenyl]‐3‐({3‐[2‐aryl‐1‐diazenyl]perhydrobenzo[d]imidazol‐1‐yl}methyl)perhydrobenzo‐[d]imidazoles ( 6 ), a new series of bis‐triazenes with different connectivity than any previous type of bis‐triazene reported. The products have been characterized principally by NMR and IR spectroscopy, elemental analysis and unequivocally by X‐ray crystallography. The methylene protons of the perhydroimidazole rings are diastereotopic giving rise to a doublet of doublets pattern in the ¹H NMR spectra. However, detailed analysis of the NMR spectra shows that there is more than one set of doublet‐of‐doublet signals, suggesting the presence of different rotameric forms of the products. The ¹³C NMR spectral assignments were assisted by COSY and DEPT experiments with selected compounds.     

Hammerstein integral equivalent of Riccati's equation

A transformation exists which allows the general Riccati equation to be written in a simpler form: The transformed equation has the equivalent nonlinear Hammerstein integral equation if the kernel N(r, r′) satisfies three conditions: and and A solution of the nonlinear integral equation is devised by repeatedly integrating the Hammerstein equation. During this procedure the kernel generates an equation that contains only coefficients of β(r)⁰ and β(r)¹. As a result, after truncating at the end of the nth cycle, it is a simple matter to write down a Padé-type approximation: all coefficients in this approximation are capable of being evaluated in terms of simple algebraic formulations of P(r), R(r), and integrals over P(r). The zeroes of the denominator of the Padé-type approximation define the points where singularities occur in β(r).     

Aphapolynins A and B, two new limonoids from the fruits of Aphanamixis polystachya

Two new highly oxidized A,B-seco limonoids, aphapolynins A (1) and B (2), were isolated from the fruits of Aphanamixis polystachya. Their structures were elucidated by spectroscopic analysis, in particular, the absolute configuration of aphapolynin A was determined by a single-crystal X-ray study using a mirror Cu Kα radiation. Aphapolynin A exhibit moderate cytotoxicities when tested against a panel of tumor cell lines.