Structure elucidation and stereoselective total synthesis of pavettamine, the causal agent of gousiekte

The structure elucidation of a novel natural product pavettamine (1), the causal agent of the plant toxicosis gousiekte, is reported. The structure was defined by analysis of NMR and MS data and the relative configuration followed from the ¹³C NMR data of the acetonide derivative. The absolute stereochemistry was established by total synthesis from (2S)-malic acid using chiral sulfoxide methodology as (2S,4R,8R,10S)-1,11-diamino-6-aza-undecane-2,4,8,10-tetraol.     

H NMR aided elucidation of products derived from photodegradation of ethyl 3-azido-4,6-difluorobenzoate in 2,2,2-trifluoroethanol

The major products formed upon photolysis of ethyl 3-azido-4,6-difluorobenzoate in 2,2,2-trifluoroethanol-d₃ has been elucidated by ¹H NMR analysis of the product mixture. Among the products formed and structurally elucidated was a hitherto unreported product formed during photolysis of aryl azides, namely azoxybenzene 19. The structural assignments of the major components of the reaction mixture were aided by comparison with ¹H NMR data from synthetic reference materials and compound isolation. MS, MS/MS, and HPLC analysis as well as UV spectroscopy was also employed in order to confirm and aid the structural analysis.     

Identification of a Unique Cationic Impurity in Preladenant™ Using Accurate MS and NMR

High resolution MS, 1D, and 2D NMR were used to determine the structure of a unique cationic impurity generated during the synthesis of Preladenant? H/D exchange experiments were performed by both MS and NMR to confirm the acidic nature of the cationic dihydroimidazole proton. The presence of three exchangeable protons was established by MS experiments and the disappearance of the C11 proton in ¹H‐NMR spectrum on equilibration with D₂O confirmed the acidic nature of the cationic dihydroimidazole proton. A piperazine ring contraction mechanism is proposed for the formation of the cationic dihydroimidazole.     

High-speed counter-current chromatographic isolation of ricinine,an insecticide from Ricinus communis

The alkaloid ricinine, an insecticide for leaf-cutting ant (Atta sexdens rubropilosa), was obtained from Ricinus communis. A two-phase solvent system composed of CH₂Cl₂/EtOH/H₂O (93:35:72, v/v/v) was used for high-speed counter-current chromatographic (HSCCC) isolation of ricinine in high yield and with over 96% purity, as determined by liquid and gas chromatography–mass spectrometry (LC–MS and GC–MS). Identification of ricinine was performed by comparison of ¹H NMR, ¹³C NMR and LC–MS/MS data.     

Three-component one-pot reaction for the synthesis of β-amide ketones

β-amide ketones were synthesised by a three-component one-pot reaction of phenylacetylene, aldehydes, and amides in anhydrous acetonitrile containing trifluoroacetic acid and acetic acid in the presence of AlCl₃ catalyst. The title compound structures were identified by ¹H NMR, ¹³C NMR, MS, and elemental analysis.     

Tacamine-type alkaloids from Tabernaemontana bovina together with their configuration determination

Eleven undescribed tacamine type alkaloids, named tabercamines A–K were isolated from leaves of Tabernaemontana bovina, together with six known alkaloids. The planar structure of the undescribed alkaloids were determined by comprehensive spectroscopic data analysis. Their absolute configuration were established based on the combination of the electronic circular dichroism and single X-ray crystal diffraction analysis. The NMR rules (in acetone-d₆) of identifying of the stereo-configuration at C-20/16 was established.     

Studies on the chemical constituents of Chinese azalea: I. The structure of rhodomollein-I,a new toxic diterpenoid

Two unknown toxic diterpenoids, rhodomollein-I and rhodomollein-II, and the known rhodojaponin-III, have been isolated from Chinese azalea (Ericaceae, Rhododendron molle G. Don). rhodomollein-I, C₂₀H₃₂O₆, colorless thin needles, [α]_D²⁰ ?6.65 (c 3.76 × 10^?2, EtOH), m. p. 241–242.5 °C. Its structure has been established as 1 through spectral analysis of ¹³C NMR, ¹H NMR, MS, IR and UV. Moreover, its stereostructure was unambiguously identified from the different threshold level line of ¹H-¹H NOESY.     

Stylissatin A,a cyclic peptide that inhibits nitric oxide production from the marine sponge Stylissa massa

A new cyclic heptapeptide, stylissatin A (1), was isolated from the Papua New Guinean marine sponge Stylissa massa. Through the use of 1D and 2D NMR spectroscopic analysis, Marfey’s method, and MS/MS analysis, its structure was determined to be cyclo-[Tyr¹–Ile²–Phe³–Pro⁴–Ile⁵–Pro⁶–Phe⁷]. Stylissatin A inhibited nitric oxide production in LPS-stimulated murine macrophage RAW264.7 cells with an IC₅₀ value of 87 μM.     

Synthesis and structure of some imines containing furoxan ring derived from isosafrole

A series of 14 imines containing furoxan and benzene rings has been prepared starting from isosafrole. The structure of reported compounds have been confirmed by elemental analysis, EI MS, UV, IR, and NMR spectroscopy. It is shown that, on treatment with Na₂S₂O₄, the nitro group on the benzene ring was reduced to amino group, but the N→O group of the furoxan ring was not. The ¹H‐ and ¹³C NMR signals are assigned based on their spin‐spin splitting patterns, in some cases, NOESY and HMBC spectra are used. The NOESY spectra indicate that for reported imines, the benzene and the furoxan rings could not be co‐planar; the imine group has E‐configuration.     

Aldingenin A, new brominated sesquiterpene from red algae Laurencia aldingensis

A new brominated bisabolene derivative, aldingenin A, was isolated from red alga Laurencia aldingensis Saito et Womersley (Ceramiales, Rodophyta). Its structure was determined by analysis of spectroscopic data (¹H and ¹³C NMR, IR, MS), including bidimensional NMR (¹H-¹H COSY, HMQC, HMBC and NOESY) and biogenetic considerations.     

Synthesis and in vitro cytotoxic activity of a natural peptide of plant origin

Present work reports the first total synthesis of a phenylalanine and glycine-rich cyclopolypeptide podacycline B by coupling of tripeptide Boc-L-phe-gly-L-phe-OH and tetrapeptide L-ala-gly-L-thr-L-ile-OMe followed by cyclization of linear heptapeptide segment. The chemical structure of the compound was elucidated by FTIR, ¹H NMR, ¹³C NMR, FAB MS spectral data and elemental analyses. The newly synthesized peptide was subjected to biological screening and found to possess high cytotoxicity against Dalton’s lymphoma ascites (DLA) and Ehrlich’s ascites carcinoma (EAC) cell lines with IC₅₀ values of 13.2 and 15.5 μM, in addition to moderate anthelmintic activity against earthworms M. konkanensis, P. corethruses and Eudrilus sp. at a dose of 2 mg ml^?1.     

Preparation and thermal studies of self-crosslinked terpolymer derived from 4-acetylpyridine oxime, formaldehyde and acetophenone

Terpolymer (4-APOFA) has been synthesized using the monomer 4-acetylpyridine oxime, formaldehyde and acetophenone in 1:5:1 molar proportion. The structure of 4-APOFA terpolymer has been elucidated based on various physicochemical techniques, i.e., FT-IR, ¹H NMR, Pyrolyis GC/MS and viscosity average molecular weight. The glass transition temperature (T_g) and thermal stability of terpolymer have been determined by DSC. The activation energy of the thermal reaction has been determined with differential scanning calorimetry using Kissinger method. The apparent activation energies (E_a) of each step during thermodegradation have been determined using Flynn-Wall-Ozawa method. The type of solid-state mechanism has been established by Craido method. From the calculation, the solid-state thermal mechanism is proposed to be D₃ (three-dimensional diffusion) at initial decomposition state and F₁ (random nucleation with one nucleus on the individual particle) at second decomposition state for 4-APOFA. It has also been shown to possess excellent antimicrobial activities as compared to other cationic resins.     

含能富勒烯吡咯烷衍生物的合成及工艺研究

利用Prato反应合成分离出了新型含硝基富勒烯吡咯烷衍生物1, 并对其工艺条件进行了研究, 探讨了反应物计量比、温度及时间对产物1产率的影响, 得到了合成产物1的最佳工艺条件: C₆₀, 间硝基苯甲醛和N-甲基甘氨酸的物质的量比为1∶1∶2, 温度为100 ℃, 反应时间为16 h, 此时产物1产率达到94.8%(以消耗的C₆₀计). 同时用UV-Vis, FT-IR, ¹H NMR, ¹³C NMR and MS spectra等光谱手段确定了产物1的分子结构.     

Synthesis, structure and insecticidal activity of some novel amides containing N-pyridylpyrazole

A novel series of amides containing N-pyridylpyrazole were designed and synthesized. All of the compounds were characterized and confirmed by IR, ¹H NMR, ¹³C NMR, MS and elemental analysis. The single crystal structure of 9d was determined by X-ray diffraction. The bioassay tests showed that the title compounds exhibited good insecticidal activities against Mythimna separata Walker, diamondback moth and Laphygma exigua Hübner.     

Synthesis of biosourced polyether-amides from 1,4-3,6-dianhydrohexitols: Characterization by NMR and MALDI–ToF mass spectrometry

New series of polyether-amides were prepared by polycondensation in solution of three diamines based on 1,4-3,6-dianhydrohexitols with two types of diacyl chlorides (sebacoyl and isophtaloyl). Unprecedented diamines based on isomannide and isoidide were elaborated. The corresponding polyether-amides (PeA) were obtained with high yields. They were characterized by different analytical techniques (NMR, MALDI–ToF MS, DSC). The combination of MALDI–ToF MS with NMR spectroscopy allowed us to confirm structure types. DSC measurements revealed an amorphous character for the isophtaloyl family with a high T_g value. The sebacoyl series proved to be semi-crystalline with a high T_m value. Isosorbide-based PeAs demonstrated interesting properties (T_g above 210 °C and T_m above 240 °C) and high viscosity (0.32).     

A New Supramolecular Assembly Formed by Melamine and Sulfuric Acid

Polymeric melaminium sulfate [(LH₂)₂(SO₄)₂]_n has been synthesized by reaction of melamine L with sulfuric acid in aqueous solution. The compound was characterized by elemental analysis, ¹H NMR, ESI MS and a single crystal X‐ray diffraction analysis. The architecture of the assembly formed is based on hydrogen bonded dimers of diprotonated melaminium cations (LH₂)²⁺ which are linked by a hydrogen bonded network with sulfate ions forming 2D sheets. A 3D polymeric structure results from the presence of mutual hydrogen bonds between sulfate ions and melaminium cations in different sheets. Significant π‐π stacking is also present between the aromatic cations in this supramolecular arrangement.     

Synthesis,characterization, antibacterial activities and carbonic anhydrase enzyme inhibitor effects of new arylsulfonylhydrazone and their Ni(II), Co(II) complexes

Ethane sulfonic acide hydrazide (esh: CH₃CH₂SO₂NHNH₂) derivatives as 5-methylsalicyl-aldehydeethanesulfonylhydrazone (5msalesh), 5-methyl-2-hydroxyacetophenoneethane sulfonylhydrazone (5mafesh) and their Ni(II), Co(II) complexes have been synthesized for the first time. The structure of these compounds has been investigated by elemental analysis, FT-IR, ¹H NMR, ¹³C NMR, LC/MS, UV–vis spectrophotometric method, magnetic susceptibility, thermal studies and conductivity measurements. The antibacterial activities of synthesized compounds were studied against Gram positive bacteria; Staphylococcus aureus, Bacillus subtilis, Bacillus magaterium and Gram negative bacteria; Salmonella enteritidis, Escherichia coli by using the microdilution broth method. The biological activity screening showed that ligands have more activity than complexes against the tested bacteria. The inhibition activities of these compounds on carbonic anhydrase II (CA II) have been investigated by comparing IC₅₀ and K_i values and it has been found that 5msalesh and its complexes have more enzyme inhibition efficiency than other compounds.     

Synthesis,crystal structure,chromatographic seperation,and thermogravimetric investigation of a ONNO type asymmetric Schiff base and its trinuclear complexes

1,3-Propanediamine was put to react with 2-hydroxybenzaldehyde and 2-hydroxyacetophenone sequentially in aprotic medium. The crystalline product was examined by high performance liquid chromatography. The composition was 66% asymmetric Schiff base N(2-hydroxybenzylidene)-N′(2-hydroxyacetophenone)-1,3-propanediamine (SALLACH₂) and 33% bis-N,N′(2-hydroxyacetophenylidene)-1,3-propanediamine (LACH2). As the crystals were uniform and of appropriate size, the molecular model of the material was revealed by X-ray diffraction. It was seen that two molecules of SALLACH₂ and one molecule of LACH₂ formed the mixed crystals. The substance was separated to its components and the asymmetric Schiff base was purified with a silica column. The substance was characterized with elemental analysis, FT-IR, MS, ¹HNMR, and ¹³C NMR. In addition, six tri-nuclear complex with the nuclear structure of Ni^II-Ni^II-Ni^II, Ni^II-Cu^II-Ni^II, Ni^II-Mn^II-Ni^II were prepared from this Schiff base and stoichiometry was determined by elemental analysis, FT-IR and thermogravimetry. Finally, the molecular structures of two complexes were brought to light by XRD which highlights the asymmetry of the ligand more clearly.     

Structure Determination of a New Chromone Glycoside by 2D INADEQUATE NMR and Molecular Modeling

The structure of a new chromone glycoside isolated from smilax glabra, named smiglanin [3,5,7-trihydroxychromone 3-O-α-L -rhamnopyranoside] (C₁₅H₁₆O₉), was determined using NMR techniques. The carbon skeleton of the molecule was established mainly by the 2D INADEQUATE method coupled with a computerized spectral analysis. Complete ¹H and ¹³C resonance assignments were made based on the INADEQUATE and other 1D and 2D NMR techniques, including long-range HETCOR and indirect detection HMBC. The vicinal proton–proton coupling constants, together with proton–proton distance constraints derived from the NOESY experiment, were incorporated as molecular modeling parameters to give the energetically most favorable conformation.