Calculation of circular dichroism spectra of michellamines A and C, based on a complete conformational analysis

The first quantum chemical calculation of the circular dichroism (CD) spectra of michellamines has been achieved, based on a complete quantum chemical conformational analysis. Michellamines are dimeric naphthylisoquinoline alkaloids and thus naturally occurring quateraryls, with a large molecular size and flexibility and equipped with stereogenic centers and axes.     

Synthesis of Naturally Occurring Pyrazine and Imidazole Alkaloids from Botryllus LeachiRID=”a”ID=”a”?Dedicated to Prof. G. M?rkl on the occasion of his 75th birthday

The synthesis of the naturally occurring and biologically active alkaloids 1 and 2, first isolated from the red ascidian Botryllus leachi by Duran et al. [1], is described and the structure proposed for Botryllazine B (1) is confirmed. The analytical data for 2-(p-hydroxybenzoyl)-4-(p-hydroxyphenyl)imidazole (2) are discussed and compared with the literature. With special emphasis of ¹H NMR data the tautomerism of aroylimidazolemethanones is described.     

Investigation of Aconitine-type Alkaloids from Processed Tuber of Aconitum carmiechaeli by HPLC-ESI-MS/MS~n

Introduction Aconitine-type alkaloids isolated from the roots of Aconitum carmiechaeli show a potential toxicity and a broad spectrum of bioactivity[1-4].On the basis of the C8-substituent of C19-diterpenoid skeleton,aconitine-type alkaloids can be divided into diester-diterpenoid alkaloids(DDAs),monoester-diterpenoid alkaloids(MDAs),and lipo-alkaloids(Fig.1).     

新型以咔唑为主链的能量转移型发光聚合物

用Suzuki偶合反应合成了一系列以咔唑为主链，与不同的芳香环和杂环化合物 共聚的新型电致发光无规共聚物．这些共聚物溶于普通的有机溶剂，发较强的荧光 ．咔唑链段为共聚物提供了很好的空穴传输和空穴注入性能．与咔唑共聚的窄能隙 单体，如蒽(ANT)、噻吩(Th)、2，1，3-苯并噻二唑(BTDZ)、2，1，3—苯并硒二唑 (BseDZ)和4，7—二噻吩—2，1，3—苯并噻二唑(DBT)在聚合物中含量小于50％时 成为陷阱中心．还观察到极为有效的分子内能量转移．由于共聚单体的能隙不同， 这些电致发光共聚物的发光范围可覆盖整个可见光谱区．研究结果表明，用咔唑作 为宽带主体，与少量低带隙单体共聚，有可能成为一种合成同时兼有优异空穴注入 特性，又能广泛调节发光颜色的新的发光聚合物体系．     

双(6-溴代-9-乙基-咔唑-3-基)甲苯基碘盐的合成

双(9-乙基-咔唑-3-基)甲苯基碘盐是一种性能优良的有机光电导体增感剂.本文合成了双(6-溴代-9-乙基-咔唑-3-基)甲苯基碘盐,其分子结构通过红外、核磁、质谱和元素分析得到证实.初步实验表明该染料具有较宽范围的光谱响应,与聚 N-乙烯基咔唑(简称 PVK)相配合具有优良的光敏性能.     

Liquid chromatographic/electrospray mass spectrometric determination (LC/ESI-MS) of chelerythrine and dihydrochelerythrine in near-critical CO2 extracts from real and spiked plasma samples

Two polar benzo[c]phenanthridine alkaloids, chelerythrine (CHE) and dihydrochelerythrine (DHCHE), were extracted at 35 °C and 10 MPa (15 MPa for real samples) from real and spiked plasma samples with acceptable recoveries (95.1% and 81.0%, respectively) using near-critical CO₂ modified with aqueous (1:1, v/v) methanol. The alkaloids were quantified by a liquid chromatographic/electrospray mass spectrometric (LC/ESI-MS) method on a Zorbax SB-CN column (75 mm × 4.6 mm, 3.5 μm particle size) using methanol (organic phase) and 50 mM ammonium formiate (aqueous phase) as a mobile phase. A linear gradient 0-1 min, isocratic at 60% organic phase (v/v); from 1.0 to 7.0 min, 60-71% organic phase (v/v); from 7.0 to 18.0 min, 71-60% organic phase (v/v) was applied. The limit of detection was 1.22 ng (3.50 pmol) for CHE and 0.95 ng (2.72 pmol) for DHCHE per 1 ml of the sample. The linearity of the calibration curves was satisfactory as indicated by coefficients of determination 0.9979 and 0.9995 for CHE and DHCHE, respectively. Repeatability and intermediate precision (average R.S.D.s) were 1.0-1.5%, accuracy was in the range 99.7-100.3%. Average recovery was 100.1% for both, standard solutions and spiked plasma extracts. Three samples of real rat plasma were extracted and analysed to test the method.     

A study of the behaviour of some new column materials in the chromatographic analysis of Cinchona alkaloids

Summary A major problem in the HPLC analysis of alkaloids is the poor peak shape and consequently low resolution, due to the interactions of the basic alkaloids with the residual acidic silanol groups of most reversed phase materials. The performance of new packing materials specially designed for the separation of basic compounds has been studied using mobile phases without the special additives commonly applied in the analysis of alkaloids. Strongly basic Cinchona alkaloids were used as test compounds. Retention characteristics and selectivities of each material were studied, after mobile phase optimisation for the column. The influence of the major factors (nature and content of the organic modifier, pH value, salt concentration) affecting resolution was studied. The mobile phases were chosen so that they could be used in thermospray LC-MS. The addition of salts to the mobile phase improves separation but in general the modification of the mobile phase gave little change in selectivity. The performance of silicabased C₁₈ material proved superior to the polymer materials tested.     

LC-ESI-MS/MS profiling of alkaloids and antiproliferative activity of Pachypoduim lamerei drake leaves

Abstract

In the present study, evaluation of the antiproliferative activity of Pachypodium lamerei Drake leaves (family Apocyaceae) against human breast cancer cell lines MDA-MB-231 was done for the total methanolic extract, crude alkaloidal mixture and ursolic acid using the MTT colorimetric assay. The methanolic extract showed the strongest antiproliferative activity followed by ursolic acid and crude alkaloidal fraction with an IC₅₀ equal to 6.2, 14.55 and 56.3?µg/ml respectively compared to oleocanthal. It is the first record for the LC/ESI-MS/MS alkaloidal profiling of the leaves of P. lamerei. Seven alkaloids were tentatively identified according to their fragmentation patterns. Four alkaloids were related to the parent indole class and two alkaloids belong to the quinoline class in addition to one steroidal alkaloid with a pregnan nucleus. Phytochemical investigation of the methanolic extract led to the isolation of three triterpenoidal compounds including ursolic acid, 11,12-didehydroursolic acid lactone and ursolic acid lactone.     

Radical amination with sulfonyl azides: a powerful method for the formation of C-N bonds

A novel reaction for the introduction of an azide moiety by means of a mild radical process is currently under development. Sulfonyl azides are suitable azidating agents for nucleophilic radicals, such as secondary and tertiary alkyl radicals. More electrophilic radicals, such as enolate radicals, do not react with sulfonyl azides. This feature allowed the development of efficient intra- and intermolecular carboazidations of olefins. Due to the versatility of the azido group, this reaction has an important synthetic potential, as already demonstrated by the preparation of the core of several alkaloids, particularly those containing an amino-substituted quaternary carbon center, such as FR901483.     

Transition metal complexes in organic synthesis. Part 68: Iron-mediated total synthesis of mukonine and mukonidine by oxidative cyclization with air as the oxidizing agent

The oxidative cyclization of 5-(2-amino-5-methoxycarbonylphenyl)-substituted tricarbonyl[η⁴-cyclohexa-1,3-diene]iron complexes by air in protic medium provides the corresponding tricarbonyl[η⁴-4a,9a-dihydro-9H-carbazole]iron complexes. This procedure is applied to the total synthesis of the 3-methoxycarbonylcarbazole alkaloids mukonine and mukonidine.