摘要:

AbstractTandem cascade reaction of one molecule of alkyl azide and four molecules of methyl vinyl ketone gives a heterocyclic compound having an 1,4‐diazepine fused to a pyrazoline and spiro‐linked to a dihydropyran. The tandem cascade reaction is composed of an intermolecular [3+2] dipolar cycloaddition to give a triazoline, an isomerization to a diazo compound, another intermolecular [3+2]dipolar cycloaddition to give a pyrazoline, a Michael addition, dehydration, and a [4+2] cycloaddit

ISSN:0009-4536    

DOI:10.1002/jccs.200300070

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractA novel approach towards the construction of the galanthamine skeleton was demonstrated by the Pd‐catalyzed cyclization ofN‐[2‐(1,4‐dioxa‐spiro[4,5]dec‐7‐en‐8‐yl)‐ethyl]‐2‐iodo‐4‐methoxy‐N‐methyl‐benzamide (23), with formation of the benzazepine ring an

ISSN:0009-4536    

DOI:10.1002/jccs.200300071

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractThe interaction of 8‐Azaguanine and fish tests double‐stranded DNA (dsDNA) and fish tests single‐stranded DNA (ssDNA) was studied electrochemically by using differential pulse voltammetry (DPV) and cyclic voltammetry (CV) at wax‐marinated graphite electrodes (GE) in a 0.2 mol/L acetate buffer (pH 3.6). Different effect factors, such as pH, time, temperature, and DNA concentration were determined. It was observed that the peak current decreased and the peak potential shifted positively with the increasing of time, temperature and DNA concentration, respectively. In addition, the peak current was a linear relationship with DNA concentration in the range of 1 μg/mL ∼ 7 μg/mL. Furthermore, the signals were found to decrease in the order of 8‐AG, 8‐AG‐dsDNA adduct and 8‐AG‐ssDNA adduct, and the signal at a bare electrode was higher than that at the dsDNA‐modified CE. Simultaneously, the electrode reaction process was investigated in detail by some electrochemistry techniques and its dynamics p

ISSN:0009-4536    

DOI:10.1002/jccs.200300072

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractA phenomenon of mixing blue and brown seawater, called “Yin‐Yang Sea”, has existed for decades in Liang‐Dong Bay. In order to determine the chemical composition and origin of pollutants in the bay, each of 5 water samples from the stream and bay were collected for chemical analyses. Meanwhile, suspension particles in the bay, the sediments on the bottom of bay and the precipitation on the bottom of the stream were also collected for chemical, X‐ray diffraction and particle size analyses.The suspension particles are amorphous and are predominantly composed of Fe(OH)3. This is showen by the solubility products of water samples in the bay being higher than the kspof Fe(OH)3. The deposits on the bottom of the stream also show similar results. However, the chemical concentrations of major ions, e.g. Na+, K+, Ca+2, Mg+2, Cl−and SO4−2, are much higher in the bay water than of the stream water. Nevertheless, Fe+2, Mn+2, Cu+2and Si+4show positive anomalies in the lower stream where the abandoned pits are located. Thus, it is assumed that minerals in the pits, such as pyrite and marcasite, are the main source supplying iron through weathering. Iron released by minerals is carried by the stream and arrives in the bay in hours. Since the oxidation rate becomes very slow in the bay because of the effects of salts and neutral pH values, most of the particles of Fe(OH)3form in the

ISSN:0009-4536    

DOI:10.1002/jccs.200300073

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY

摘要:

AbstractBioassay‐directed fractionation of the acetone extract ofClavularia inflatacollected in Green Island has afforded two new dolabellane diterpenoids, designated as clavinflols A (4) and B (5) in addition to the reported (1R*,12R*)‐dolabella‐4(16),7,10‐triene‐3,13‐dione (1), stolonidiol (2) and stolonidiol monoacetate (3). The structures of compounds4and5were determined on the basis of 1D and 2D‐NMR techniques including COSY, HSQC, HMBC and NOESY experiments, and acetylation which yielded derivatives6and7, respectively. Pharmacological study revealed that compounds1–3and5exhibited cytotoxicity against human oral epidermoid carcinoma (KB) cells while compound4showed selective activity toward h

ISSN:0009-4536    

DOI:10.1002/jccs.200300074

出版商:WILEY‐VCH Verlag    

年代:2003

数据来源: WILEY