Multiple binding modes of the camptothecin family to DNA oligomers

The binding constants of camptothecin, topotecan and its lactone ring-opened carboxylate derivative to DNA octamers were measured by UV and NMR spectroscopy. The self-association of topotecan (TPT) was also measured. The carboxylate form of TPT binds in the same way as the lactone, but more weakly. Titration of TPT into d(GCGATCGC)2 shows a preferred location stacked onto the terminal G1 base. However, the intermolecular NOEs cannot be reconciled with a single conformation of the complex, and suggest a model of a limited number of conformations in fast exchange. MD calculations on four pairs of starting structures with TPT stacked onto the G1-C8 base pair in different orientations were therefore performed. The use of selected experimental "docking" restraints yielded ten MD trajectories covering a wide conformational space. From a combination of calculated free energies, NOEs and chemical shifts, some of the structures produced could be eliminated, and it is concluded that the data are consistent with two major families of conformations in fast exchange. One of these is the conformation found in a crystal of a TPT/DNA/topoisomerase I ternary complex [Proc. Natl. Acad. Sci. USA 2002, 99, 15 387-15 392].     

New Stephaoxocane Alkaloids from Stephania longa

Three new stephaoxocane‐type alkaloids, stephalonganines A–C ( 1 – 3 ), together with the known eletefine ( 4 ), were isolated from the whole plant of Stephania longa. Their structures were fully characterized spectroscopically, and the absolute configurations of the new alkaloids were assigned by comparison of their circular‐dichroism (CD) data with those of 1,2‐dihydrostephaoxocanine ( 5 ), in combination with 2D‐NMR experiments.     

A novel palladium-catalyzed synthesis of β-carbolines: application in total synthesis of naturally occurring alkaloids

Two naturally occurring β-carbolines, 6-methoxy-2-methyl-1,2,3,4-tetrahydro-β-carboline and bauerine A, have been prepared using a Stille-type coupling, followed by a palladium-phosphine catalyzed N-heteroannulation as the key steps.     

海洋天然产物研究新进展

海洋天然产物化学是目前天然产物化学中最活跃的研究领域之一。近年来,从海洋生物中分离到非常多的化学结构和生理活性上令人注目的新化合物,引起了有机化学家和药物化学家的关注。本文按萜类、太环内酯、聚醚类、生物碱,环肽、含氰化合物、甾醇、聚丙酸酯类化合物等化学结构来概述海洋天然产物研究近年来的进展。     

Two Novel Sub-skeleton Types of ent-Kauranoids from Isodon gesneroides

Two novel ent-kauranoids with new sub-skeleton types, gesneroidins G and H were isolated as white powder from the ether extract of the leaves of Isodon gesneroides through normal phase column chromatography. Their structures were elucidated as 3β,6α,7β-triacetoxyl-15-hydroxyl-14-oxo-ent- 15,16-seco-kaur-11,17-olide and Iα-hydroxyl-3β,6α,7β,11 β-tetraacetoxyl-ent-nor-15,17-kaur-8,16-olide on the basis of the spectral evidences including ID and 2D NMR spectra.     

Separation and Determination of Ephedrine Enantiomers and Synephrine by High Performance Capillary Electrophoresis in Dietary Supplements

The chiral separation of ephedrine alkaloids by high performance capillary electrophoresis is of great interest since the enantiomers exhibit quantitative and qualitative differences in pharmacological activity. The isomers of (–)-ephedrine, (+)-pseudoephedrine, (–)-N-methylephedrine, (+)-N-methylpseudoephedrine, (+)-norpseudoephedrine and (–)-norephedrine are the major bioactive components of E. sinica (Ma-Huang) which is a Chinese herb used for weight loss and as an energy booster in the US. However, the compounds stereoisomers are not present in the plant material. The electrophoretic separation was performed using a 110 cm × 50 m I.D. (101.5 cm effective length) fused silica capillary. The samples were injected by pressure for 5 s at 50 mbar and the running voltage was 30 kV at the injector end of the capillary. Within 23 min, nine ephedrine compounds and synephrine were separated at 210 nm. The method was successively applied to the determination of the ephedrine compounds in dietary supplement products. Parameters affecting the resolution between (+) and (–)-enantiomers, such as pH, cyclodextrin concentration, temperature, organic modifier, buffer concentration and capillary dimensions were reported.     

二维高效液相色谱技术用于分析中药制剂中麻黄类生物碱

构建了一个离线的二维高效液相色谱系统,以解决成分复杂的中药样品的分离和痕量组分的定量问题。该系统在原有的单泵、单检测器高效液相色谱仪的基础上作了相应的改进而构成,样品先在第一维的Zor-bax SB-C18色谱柱中进行分离之后,利用一个六通切换阀将目标组分切换并收集,浓缩后再注入第二维的Ai-chrom Bond-AQ C18色谱柱中进行分离。利用上述方法对3种麻黄类生物碱进行了二维分离和分析,实验结果表明,样品的分离明显改善,并且这个系统可用于中药的直接进样分析。     

V. Thioanalogues of sparteine lactams. (+)-2-Thiono-17-oxosparteine and (+)-2,17-dithionosparteine

The X-ray and spectroscopic results clearly indicate that the (+)-2-thiono-17-oxosparteine (1) and (+)-2,17-ditihionosparteine (2) are conformationally rigid. In order to analyze deviations of lactam/thiolactam groups from planarity induced by ring constraints, the Dunitz-Winkler approach has been used. The lactam and thiolactam groups are close to planarity, only the lactam group in one of the two independent molecules of 1 is markedly non-planar. The bond angles in the thiolactam and lactam groups are highly diverse. Rings A and C adopt a distorted sofa conformation in both compounds. The distortions in the molecules of 2 as compared with those in the related monothiolactams correspond to the unusual chemical shifts of H5(eq), H5(ax) and H11, as well as to the extremely low J_5ax-6 and extremely large J_5eq-6 coupling constants. Also chemical shifts show a similar regularity being extremely high and low for C2 and C17, respectively.     

Herstellung von 6,14-Ethenomorphinan-Derivaten

Zusammenfassung Dihydronorthevinon (2b) wurde aus Dihydrothevinon (2a) mit Azodicarbonsäurediethylester (DEAD) hergestellt und zu einigen neuen N-substituierten Dihydronorthevinon-Derivaten (2c–2g) umgesetzt. Es wurdenGrignard-Reaktionen dieser Verbindungen mit Methylmagnesiumiodid bzw.tert-Butylmagnesiumchlorid durchgeführt. O-Demethylierungen von3a–3j ergaben die entsprechenden N-substituierten Buprenorphin- bzw. Diprenorphin-Analoga4a–4j.

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Preparation of 6,14-ethenomorphinan derivatives

Summary Dihydronorthevinone (2b) was prepared from dihydrothevinone (2a) with diethyl azodicarboxylate (DEAD) and transformed into a number of new N-substituted dihydronorthevinone derivatives (2c–2g).Grignard reactions of the new compounds with methylmagnesium iodide andtert-butyl-magnesium chloride were studied. O-Demethylation of3a–3j resulted in the corresponding N-substituted buprenorphine and diprenorphine analogs4a–4j.

     

吗啡烷型生物碱类药物的化学发光分析法研究

雷氏盐（ＮＨ４Ｃｒ（ＮＨ３）２（ＳＣＮ）４）．Ｈ２Ｏ）是生物碱类物质的沉淀剂，经研究发现，雷氏盐可以催化鲁米诺与过氧化氢的化学发光反应，而吗啡烷型生物碱能沉淀雷氏盐，可导致鲁米诺－过氧化氢－雷氏盐体系化学发光强度的降低，根据这一发现，本文建立了吗啡烷型生物碱类药物（吗啡，青藤碱，可待因）的流动注射化学发光分析方法，方法有较低的检出限，较宽的线性范围和较好精密度用于一些药物的测定，结果较为满意。