Structure of securinine

The structure (XXVII) proposed for securinine is confirmed by synthetic structural proof of the key degradation products, lactam-carbinol B (XXIII) and quinolizidine B (XX).     

Unexpected ring contraction and oxidation rearrangement reactions of securinine

The bromination and oxidation of securinine were studied. An interesting and surprising rearrangement was observed during the reaction of securinine with tribromo-isocyanuric acid or 1,3-dibromo-5,5-dimethylhydantoin in methanol, yielding a stereoselective ring contraction norsecurinine derivative. Meanwhile two oxidation rearrangement products were also reported. Some preliminary discussions on the reactivity of securinine were conducted from these rearrangements; it is believed to be induced by alkaline nitrogen atom of the molecule.     

一叶萩碱A环的引入

一叶蔌碱具有士的宁样生理作用,可兴奋中枢并升高血压。临床方面用于治疗面神经麻痹,小儿麻痹后遗症等疾病。其结构已确定为1。     

Chiroptical study and absolute configuration of securinine oxidation products

Time-dependant density functional theory–electronic circular dichroism spectra prediction was carried out to study the absolute configuration of phyllanthidine-type derivatives 5 and 6, derived from securinine (1) and its enantiomer virosecurinine (2), respectively. This method demonstrated to be very reliable in this alkaloid series. Thus, 5 and 6 shared the same stereochemistry as their parent precursors, confirming the retentive nature of the oxidation sequence. In addition, this study highlighted the key role of the methylene bridge (BC ring) in the chiroptical activity of these compounds. These results fully clarified the stereochemical relationships between the phyllanthidine and the securinine subgroups.     

First diastereoselective chiral synthesis of (-)-securinine

[reaction: see text] A diastereoselective total synthesis of securinine in optically pure form was achieved by employing ring-closing metathesis of the corresponding dienyne compound as a key step.     

N-amination of tertiary amines : A novel method for 1,1,1-trisubstituted hydrazinium salts

A novel method for the preparation of 1,1,1-trisubstituted hydrazinium salts by the reaction with O-mesitylenesulfonylhydroxylamine (MSH) is described. The N-amine salts of some selected alkaloids were prepared. The stereochemistry of N-amination of securinine and allosecurinine with MSH was also investigated.     

一叶秋碱全合成的研究-中间体α-羟酮的合成

α-羟酮是中枢神经药物叶 碱 合中的重要中间体。本文以不同路线合成了α羟酮, 并通过与天然降解物进行光谱对照确定了结构。     

体液中-叶萩碱检测方法的研究

本文报道了用气相色谱(GC)及气相色谱-质谱联用(GC/MS)检出人体液中一叶萩碱的方法.尿样经碱化后用乙醚直接萃取,回收率为72.1％;血浆样品用Sep-pak小柱提取,回收率为 43.9％,GC/MS的检测限为 20ng.方法快速、简便、准确.     

A new general access to either type of Securinega alkaloids: synthesis of securinine and (-)-allonorsecurinine

The syntheses of securinine and (-)-allonorsecurinine have been achieved starting from easily available alpha-amino acid derivatives and using as key steps a RCM and a Heck reaction for the formation of rings D and C, respectively. [reaction: see text]     

An approach to the skeleton of the securinega alkaloids. The total synthesis of (+/-)-securinine

[structure: see text]. The concise total synthesis of securinine in nine steps from readily available starting materials is described. Key steps of the synthesis include an addition of a silyloxyfuran to an in situ generated iminium ion and a novel ring closing metathesis reaction.     

Synthesis and biological activity of amination products of the alkaloid securinine

A method for stereospecific synthesis of allomargaritarin and other amination products of the natural alkaloid securinine was developed. Stereoselective nucleophilic addition of an amine at the double bond of the azobicyclooctane moiety of securinin was achieved by using ytterbium triflate as the catalyst. The biological activity of securining caused by adding pharmacophores to the molecule was shown to change experimentally. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 156–160, March–April, 2008.     

Secu'amamine A, a novel indolizidine alkaloid from Securinega suffruticosa var. amamiensis

A novel indolizidine alkaloid, secu'amamine A (1), was isolated from the leaves and twigs of the medicinal plant, Securinega suffruticosa var. amamiensis together with securinine (2). The structure and relative stereochemistry of 1 was elucidated by spectroscopic data and its absolute configuration was assigned on the basis of the OMe-madelate method.     

Total syntheses of the Securinega alkaloids (+)-14,15-dihydronorsecurinine, (-)-norsecurinine, and phyllanthine

A new strategy for enantiospecific construction of the Securinega alkaloids has been developed and applied in total syntheses of (+)-14,15-dihydronorsecurinine (8), (-)-norsecurinine (6), and phyllanthine (2). The B-ring and C7 absolute stereochemistry of these biologically active alkaloids originated from trans-4-hydroxy-L-proline (10), which was converted to ketonitrile 13 via a high-yielding eight-step sequence. Treatment of this ketonitrile with SmI2 afforded the 6-azabicyclo[3.2.1]octane B/C-ring system 14, which is a key advanced intermediate for all three synthetic targets. Annulation of the A-ring of (-)-norsecurinine (6) with the required C2 configuration via an N-acyliminium ion alkylation was accomplished using radical-based amide oxidation methodology developed in these laboratories as a key step, providing tricycle 33. Annulation of the D-ring onto alpha-hydroxyketone 33 with the Bestmann ylide 45 at 12 kbar gave (+)-14,15-dihydronorsecurinine (8). In the securinine series, the D-ring was incorporated using an intramolecular Wadsworth-Horner-Emmons olefination of phenylselenylated alpha-hydroxyketone 47. The C14,15 unsaturation was installed late in the synthesis by an oxidative elimination of the selenoxide derived from tetracyclic butenolide 50 to give (-)-norsecurinine (6). The A-ring of phyllanthine (2) was formed from hydroxyketone 14 using a stereoselective Yb(OTf)3-promoted hetero Diels-Alder reaction of the derived imine 34 with Danishefsky's diene, affording adduct 35. Conjugate reduction and stereoselective equatorial ketone reduction of vinylogous amide 35 provided tricyclic intermediate 36, which could then be elaborated in a few steps to stable hydroxyenone 53 via alpha-selenophenylenone intermediate 52. The D-ring was then constructed, again using an intramolecular Wadsworth-Horner-Emmons olefination reaction to give phyllanthine (2).     

有机颜料与表面活性剂DBS混合物的光催化降解

以TiO₂为光催化剂,研究了表面活性剂十二烷基苯磺酸钠(DBS)和有机颜料耐晒大红BBN(BBN)为混合组分的光催化降解,结果表明,pH值、底物的用量对体系的降解有显著影响,在碱性条件下,DBS的降解速率相对较快,而在酸性环境时,颜料的降解较快,在TiO₂等电点时,降解最慢,酸性条件下, TiO₂对BBN和DBS的吸附性比在碱性和中性环境中大,BBN/DBS体系中, DBS增大了BBN的水溶性,但是没有明显提高BBN的降解褪色速度,DBS浓度为0.42 g/L时,颜料降解最快,0.042 g/L时次之,2.1 g/L时最低,在BBN降解过程中DBS自身也被降解,且略有促进作用。     

Enzymatic degradation of model cellulose films

Enzymatic degradation of model cellulose films prepared by a spin-coating technique was investigated by ellipsometry. The cellulose films were prior to degradation characterized by ellipsometry, contact angle measurements, ESCA (electron spectroscopy for chemical analysis) and AFM (atomic force microscopy). At enzyme addition to preformed cellulose films an initial adsorption was observed, which was followed by a total interfacial mass decrease due to enzymatic degradation of the cellulose films. The degradation rate was found to be constant during an extended time of hours, whereafter the degradation leveled off. In parallel to the decreased interfacial mass, the cellulose degradation resulted in a thinner and more dilute interfacial film. At long degradation times, however, there was an expansion of the cellulose film. The enzyme concentration affected the degradation rate significantly, with a faster degradation at a higher enzyme concentration. The effects of pH, temperature, ionic strength and stirring rate in the cuvette were also investigated.     

Bioremediation of Single and Mixture of Pesticide-Contaminated Soils by Mixed Pesticide-Enriched Cultures

In the present study, degradation efficiencies for individual as well as mixed pesticide in different Indian soils, by mixed pesticide-enriched cultures, were evaluated under submerged and unsaturated conditions, Lindane (L), methyl parathion (MP), carbofuran (C), and a mixture of L, MP, and C were used in the study. For all the various conditions considered, methyl parathion degradation was the maximum and lindane degradation was the minimum. The degradation kinetics of the pesticides in sandy, clayey, compost, and red soils by various microbial isolates were studied. It was observed that adsorption was maximum and degradation of pesticides was minimum in compost soil. The degradation efficiencies of pesticides in liquid phase associated with soil sediment were less than those under the normal liquid phase conditions as leaching of pesticides from soil phase was continuous. Pesticide degradation was more in submerged soils compared to that in unsaturated soils. The degradation by-products of individual and mixed pesticides in liquid, unsaturated, and submerged soils were identified. Different metabolites were produced under submerged and unsaturated conditions.     

Accelerated plasma degradation of organic pollutants in milliseconds and examinations by mass spectrometry

The rapid degradation of organic pollutants, process monitoring and online controlling to obtain advanced products and decreased by-products are great and challenging tasks in environmental treatments. Herein, an accelerated plasma degradation in milliseconds was achieved by combining electrospray-based acceleration and plasma-based degradation. Taking the degradation of chloroaniline as an example, 97% of the degradation can be achieved in milliseconds. The velocity distribution of droplets was determined to be 40–50 m/s after being degraded for 0.30 ms, which exhibited different degradation behaviors in different milliseconds. Simultaneously, by virtue of the real-time and on-line detection ability of ambient mass spectrometry, intermediates, by-products and advanced products were monitored. Therefore, degradation mechanisms for different degradation times were proposed, which would provide theoretical guidance on obtaining efficient and green degradation. The fabrication, examining and understanding of accelerated plasma degradation not only enlarged application of accelerated reactions, but also promoted green and efficient degradation for environmental treatments.     

Thermo-oxidative degradation of ultrahigh molecular weight poly(ethylene oxide) in volatile organic solvents

The degradation of ultrahigh molecular weight poly(ethylene oxide) (UHMWPEO) was investigated in three volatile organic solvents, methanol, chloroform, and tetrahydrofuran. Particularly, degradation rate was determined by means of Ubbelohde viscometry and degradation products were characterized by using electron spin resonance spectroscopy (ESR) and Fourier transform infrared spectroscopy (FTIR). The highest degradation rate was observed for UHMWPEO in tetrahydrofuran, with the lowest one in methanol. The ESR results showed that PEO-C• and •OH radicals were produced during the degradation process. Among these selected solvents, tetrahydrofuran was found to generate free radicals through an autoxidation mechanism. This would accelerate the degradation of UHMWPEO, resulting in the observed highest degradation rate in the UHMWPEO/tetrahydrofuran solution. Esters were also detected in the degradation products of these UHMWPEO solutions, while formates and formate ions were generated in the solutions of UHMWPEO/tetrahydrofuran and UHMWPEO/cloroform except for PEO/methanol. Furthermore, the degradation mechanism of UHMWPEO was deduced. This work enabled an in-depth understanding on the thermo-oxidative degradation mechanism of UHMWPEO in representative organic solvents, which would be instructive for developing optimal solution-based processing technique of UHMWPEO.     

Kinetics of thermo-oxidative degradation of polypropylene/aluminum trihydroxide/organo Fe-montmorillonite nanocomposites

In the article, the thermal oxidative degradation kinetics of pure polypropylene/aluminum trihydroxide (PP/ATH) and PP/ATH/organo Fe-montmorillonite (Fe-OMT) nanocomposites were investigated using Kissinger, Friedman and Flynn–Wall–Ozawa methods. The results showed that thermal oxidative degradation of PP/ATH/Fe-OMT nanocomposites to PP/ATH were complex reaction: the whole process of thermal oxidative degradation were composed with the decomposition of ATH, the cracking and charring of the backbone chains of PP, and the oxidative degradation of char, which the curses of energy mutative with the process of thermal oxidative degradation. The control steps were different in each degradation stage. The activation energy was high in the original degradation stage. It was due to the molecular structure and may closely relate with onset temperature. In the intermediate process, the activation energy was low. In the last stage of the degradation, the activation energy was graveled because the carbon may be oxidized. In the whole process of thermal oxidative degradation, the activation energy of PP/ATH/Fe-OMT nanocomposite was higher than that of PP/ATH.     

Oxidative and photooxidative degradation of poly(acrylic acid)

The oxidative degradation of poly(acrylic acid) (PAA), a water soluble polymer, was studied at various temperatures with different concentrations of persulfates, potassium persulfate (KPS), ammonium persulfate (APS) and sodium persulfate (SPS). The photodegradation of PAA was also examined with APS as oxidizer. The degraded samples were analyzed for the time evolution of molecular weight distribution by gel permeation chromatography. A theoretical model based on the continuous distribution kinetics was developed that accounted for the polymer degradation and the dissociation of persulfate. The rate coefficients for the oxidative and photooxidative degradation of PAA were determined from the parametric fit of the model with experimental data. The rate of degradation increased with increasing amount of persulfate in both oxidative and photooxidative degradation. The rate of degradation also increased with increasing temperature in the case of oxidative degradation.