Studies related to the total synthesis of the sesquiterpene core of the pyrrolobenzoxazine natural products CJ-12662 and CJ-12663

A highly effective procedure is reported to synthesize a substituted bicyclo[4.2.0]octenol derivative by regioselective cycloaddition of phenyl-1-propynyl sulfide with cyclohexenone followed by selective reduction of the ketone group and reductive elimination of phenylsulfonyl group. The strained cyclobutene ring was then engaged in a ring-opening/cross metathesis sequence in the presence of Hoveyda-Grubbs 2nd generation catalyst. The synthesis serves as a model study toward the synthesis of the sesquiterpene diol portion of the terpenoid pyrrolobenzoxazine alkaloids, CJ-12662 and CJ-12663.     

N^2-（1-Methoxycarbonylethyl）guanosine, a new nucleoside coupled with an amino acid derivative from Amanita exitialis

A new purine nucleoside coupled with an amino acid derivative,N~2-(1-methoxycarbonylethyl)guanosine 1,along withβ-carboline and russulaceramide was isolated from the fruiting bodies of Amanita exitialis,a newly described poisonous mushroom. Its structure was elucidated by spectroscopic methods.This is the first report of naturally occurring nucleosides in which anα-amino acid derivative is bonded through itsα-amino nitrogen to a nucleobase aglycone by a C-N bond.The new compound was found to be toxic in ...     

南海红树林内生真菌ZSU-H26生物碱类代谢产物的研究

海洋微生物资源由于具有可持续开发性,而且其活性物质不像来源于其它海洋生物(如海绵、海藻、海兔、珊瑚等)产生的生物活性物质,其生产不受天然资源难再生的限制,能通过发酵进行胞外生产,与现代微生物技术相结合,较容易实现工业化生产,特别是其生产不对环境造成危害,符合当今绿色化学发展的方向.     

LCST demixing in poly(vinyl methyl ether)/water studied by means of a High Resolution Ultrasonic Resonator

The inhibitory effects of three berberine alkaloids (BAs) from Coptis chinensis Franch on Bifidobacterium adolescentis growth were investigated by microcalorimetry. The growth rate constant (k) and maximum heat-output power (Pmax) decreased and peak time of maximum heat-output power (tp) prolonged with the increase of BAs concentration. Half inhibitory ratios (IC50) BAs were respectively 790.3 (berberine), 339.6 (coptisine) and 229.8 μL⁻¹ (palmatine), which indicated the sequence of their antimicrobial activity: berberine<coptisine<palmatine. Combined with previous findings, the sequence which could show the bioactivity of Bacillus shigae and Escherichia coli was: berberine>coptisine>palmatine. The structure-function relationship of BAs indicated that the functional group methylenedioxy or methoxyl at C2 and C3 might be the major group inducing the activities of BAs on E. coli and B. adolescentis. Meanwhile, the substituent groups at C2, C3, C9 and C10 almost had equal effect on B. shigae.     

Enantioseparation of chiral sulfonates by liquid chromatography and subcritical fluid chromatography

Tert‐butylcarbamoyl‐quinine and ‐quinidine weak anion‐exchange chiral stationary phases (Chiralpak® QN‐AX and QD‐AX) have been applied for the separation of sodium β‐ketosulfonates, such as sodium chalconesulfonates and derivatives thereof. The influence of type and amount of co‐ and counterions on retention and enantioresolution was investigated using polar organic mobile phases. Both columns exhibited remarkable enantiodiscrimination properties for the investigated test solutes, in which the quinidine‐based column showed better enantioselectivity and slightly stronger retention for all analytes compared to the quinine‐derived chiral stationary phase. With an optimized mobile phase (MeOH, 50 mM HOAc, 25 mM NH₃), 12 of 13 chiral sulfonates could be baseline separated within 8 min using the quinidine‐derivatized column. Furthermore, subcritical fluid chromatography (SubFC) mode with a CO₂‐based mobile phase using a buffered methanolic modifier was compared to HPLC. Generally, SubFC exhibited slightly inferior enantioselectivities and lower elution power but also provided unique baseline resolution for one compound.     

Decomposition of N‐hydroxylated compounds during atmospheric pressure chemical ionization

N‐Hydroxylated polyamine derivatives were found to decompose during the ionization process of liquid chromatography‐atmospheric pressure chemical ionization‐mass spectrometry (LC‐APCI‐MS) experiments. The phenomenon was studied with a model compound, a synthetic N‐hydroxylated tetraamine derivative. It was found that reduction, oxidation and water elimination occurred during APCI to generate the corresponding amine, N‐oxide, and imine. The investigation further revealed that decomposition of hydroxylamines during APCI depends upon the concentration of the analyte and on the acidity of the solution introduced into the ionization source. The pH‐dependence of decomposition was utilized for the development of an MS method that allows for the unambiguous identification of N? OH functionalities. This method was applied for the study of natural products including polyamine toxins from the venom of the spider Agelenopsis aperta and mayfoline, a cyclic polyamine derivative of the shrub Maytenus buxifolia. Copyright © 2009 John Wiley & Sons, Ltd.     

Mesembrine合成方法综述

蕃杏科生物碱Mesembrine由Bodendorf研究小组于1957年从Mesembryanthemum tortuosum中分离得到.由于其结构特征和有趣的生物活性引起大量的关注.在过去的40年间,该化合物成为合成有机化学感兴趣的目标分子之一.到目前为止,文献中报道的全合成和形式合成路线已有40多种.对其中的31种全合成及形式合成路线进行了综述.     

抗肿瘤活性四氢异喹啉生物碱全合成研究进展

综述了近年来抗肿瘤活性四氢异喹啉生物碱Renieramycin,Ecteinascidin和Quinocarcin的全合成研究进展,对其构环顺序和方法进行了分析,对部分合成路线的优缺点进行了讨论.     

高效液相色谱/质谱联用技术在天然来源生物活性成分快速识别中的应用

天然来源生物活性成分是药物先导分子的重要源泉之一,它们种类繁多,结构复杂多样,逐一分离提取纯化然后进行结构分析鉴定的这一传统植物化学(天然药物化学)研究模式尽管已沿袭多年,但往往费时费力,目标性不强,且常常忽略含量甚少的微量成分.高效液相色谱及多级质谱联用技术(HPLC/MSn)兼顾了色谱的高效分离能力和质谱的强大定性功能,为天然生物活性成分的分析研究提供了新途径.本文总结了我们课题组近年来对糖苷、植物酚类以及酰胺类生物碱等几类天然有效成分的分析研究进展:应用HPLC/MSn联用技术在线分析鉴定多种天然来源的已知成分,快速筛选出多种未知成分,并运用多级质谱技术获得未知成分的结构信息,为快速准确发现新的目标结构提供靶向指导.这一研究方法的应用,突破了传统分离分析的束缚,为现代植物化学或天然药物化学研究提供了新思路.     

N.M.R. Spectral Studies of Some Quinolone Derivatives. Effect of Substitution on the Degree of Hydrogen Bonding

The chemical shift of the NH protons for a series of monomethyl-, dimethyl- and trimethyl- substituted 2- and 4- quinolones has been studied. Compounds with an 8-methyl substituent exhibit a characteristic upfield shift which is considered to be due to a reduction in hydrogen bonding as a result of steric effects. The application of this effect to the identification of alkyl substituted quinolones and some natural products is discussed.