摘要:

AbstractA novel mixed‐mode stationary phase for open tubular capillary electrochromatography (CEC) was prepared. With 3‐aminopropyltrimethoxysilane as the spacer, the chemical reagent in conjunction with the fullerene played an important role in the electrochromatographic separation of the plant phenols. The fullerene C 60‐based column has the properties of both hydrophilic and hydrophobic interaction sites and provides a positively charged capillary surface responsible for the reversed electroosmotic flow (EOF) in the column during CEC operation. Comparative studies for the fullerene‐bonded phase, the intermediate phase with amino group and the bare fused‐silica were carried out. Under the conditions of acetate buffer (20 mM, pH 5.0) and applied voltage of −15 kV, the separation of catechin, salicylic acid, myricetin, quercetin, gallic acid, caffeic acid andp‐coumaric acid could be achieved. The proposed method was also applied to the analysis of plant phenols i

ISSN:0009-4536    

DOI:10.1002/jccs.200100150

出版商:WILEY‐VCH Verlag    

年代:2001

数据来源: WILEY

摘要:

AbstractHighly protected mannosamine derivatives are synthesized from protected glucose derivatives having a free hydroxy group at C2position. Indium‐mediated allylation of protected mannosamine derivatives is investigate

ISSN:0009-4536    

DOI:10.1002/jccs.200100151

出版商:WILEY‐VCH Verlag    

年代:2001

数据来源: WILEY

摘要:

AbstractMonoalkenylferrocenes were prepared from 1,1′‐diacetylferrocene and appropriate benzyl bromides by the promotion of samarium diiodide. A practical method for preparation of both symmetric and unsymmetric dialkenylferrocenes was also explored. The reactions were stereoselective to give only (E) double bonds. The unsymmetric dialkenylferrocene bearing electron‐donating substituent (e.g. methoxy group) and electron‐withdrawing substituent (e.g. cyano group) on different phenyl rings likely exhibits a large nonlinear optical p

ISSN:0009-4536    

DOI:10.1002/jccs.200100152

出版商:WILEY‐VCH Verlag    

年代:2001

数据来源: WILEY

摘要:

AbstractThe solvolysis of 1‐tert‐butyl‐1‐(4‐phenoxy)methyl bromide (5b) and chloride (5c) in a variety of solvents were carried out. Limiting SN1 mechanisms were suggested from the observation of linear relation ships using single‐parameter Winstein‐Grunwald type correlation between logarithm of rate constants with YxBnBrandYxBnClscales, respectively. This result indicated positive charge delocalization over both arylrings and provided further evidence for possible contribution of non‐canonical resonance structure in the cationic t

ISSN:0009-4536    

DOI:10.1002/jccs.200100153

出版商:WILEY‐VCH Verlag    

年代:2001

数据来源: WILEY

摘要:

AbstractTwenty‐seven compounds including eight long‐chain hydrocarbons, 1‐hexacosanol (1), 1‐octacosanol (2), palmitic acid (3), stearic acid (4), oleic acid (5), linoleic acid (6), heptacosyl eicosanate (7), glyceryl‐1‐tetraeicosanoate (8); three sterols, β‐sitosterol (24), stigmasterol (25), β‐sitosteryl‐3‐O‐D‐glucopyranoside (26); one triterpene, lupeol (27); eight anthraquinones, chrysophanol (9), emodin (10), physcion (11), citreorosein (12), rhein (13), rhein methyl ester (14), ziganein (15), 1,4,5‐trihydroxyanthraquinone (16); two coumarins, isoscopoletin (17), scopoletin (18); two chromones, 2,5‐dimethyl‐7‐hydroxychromone (19), 2,5‐dimethyl‐7‐methoxychromone (20); three aromatic compounds, isovanillic acid (21), vanillic acid (22), and 2,4‐dihydroxybenzaldehyde (23), were isolated and identified from the bark ofCassiafistula. Their structures were

ISSN:0009-4536    

DOI:10.1002/jccs.200100154

出版商:WILEY‐VCH Verlag    

年代:2001

数据来源: WILEY

摘要:

AbstractA series of N,N,N,N′‐tetraaryl(Ar12Ar22)‐1,1′‐biphenyl‐4,4′‐diamine were synthesized by the Pd(0) catalyzed C‐N bond formation methodology. The physical properties, including glass transit ion temperature (Tg), melting point (Mp) and oxidation potential were measured. For Ar1= 2‐naphthyl and Ar2= 3‐toly (4f) and Ar2= 3‐ethylphenyl (4h), the DSC charts indicate that they have Tg, but no observable Mp. These two compounds are amorphous in solid state. The X‐ray powder diffraction pat ternof4ffurther confirmed that it is truly amorphous through out the temperature range in which it is solid. There fore, we have demonstrated that a low molecular weight organic solid can be amorphous. This is an important aspect in the prep a ration of morphologically stable amorphous thin film. Other compounds with Ar1= Ph, 1‐naphthyl while Ar2= 3‐toly or 3‐ethylphenyl are normal compounds with both Tg and Mp when prepared in their glassy state by rapid cooling of their melt. The oxidation potentials for compounds with Ar1= 1‐naphthyl and 2‐naphthyl and identical Ar2are exactly the same. The molecular structural features must be important factors for an organic

ISSN:0009-4536    

DOI:10.1002/jccs.200100155

出版商:WILEY‐VCH Verlag    

年代:2001

数据来源: WILEY

摘要:

AbstractPolydiphenylsiloxane‐co‐polydimethylsiloxane (PDPS/PDMS) statistical and reshuffled copolymers with different compositions have been synthesized and characterized. The phase behaviors of these copolymers are studied by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Critical compositions for the appearance of the thermal transitions were determined. The thermal transition properties, such as temperature and peak shape, were correlated to the structures of the copolymers. Effect of the monomer sequencing on the mesophase transition behaviors was exami

ISSN:0009-4536    

DOI:10.1002/jccs.200100156

出版商:WILEY‐VCH Verlag    

年代:2001

数据来源: WILEY

摘要:

AbstractA silica‐base chiral stationary phase (CSP) derived from L‐alanyl‐ and piperidinyl‐disubstituted cyanuric chloride was prepared for the enantioseparation of methyl esters of N‐(3,5‐dinitrobenzoyl)amino acids and amino alcohols. This CSP provides good chiral recognition and effective separation of enantiomers of both methyl esters of N‐(3,5‐dinitrobenzoyl)amino acids, except for proline, and N‐(3,5‐dinitrobenzoyl)amino alcohols by high‐performance liquid chromatography. The enantioselectivity depends mainly on three preferential interactions which include a π‐π interaction and two hydrogen‐bonding interactions. However, steric interaction between substituents attached to the chiral center of chiral selectands and the chiral selector also plays a significant role in chiral recognition. Comparison of chromatographic results of the CSP prepared in this study with those of the CSP containing pyrrolidinyl group attached to the s‐triazine moiety, reported previously (J. Chromatogr. A, 722 (1996) 189), reveals that influences of steric interaction and the basic nature of piperidinyl substituent attached to the s‐triazine ring of the chiral selector on chiral disc

ISSN:0009-4536    

DOI:10.1002/jccs.200100157

出版商:WILEY‐VCH Verlag    

年代:2001

数据来源: WILEY

摘要:

AbstractTwo new sesquiterpenes, 8,9‐secocedrachinol (1), (+)‐1‐hydroxy‐1,3,5‐bisabolatrien‐10‐one (2) and two new lignans, (7R,8S)‐9′‐(β‐rhamnopyranosyl)‐3‐methoxy‐3′:7,4′:8‐diepoxyneolignan‐4,9‐diol (3), and (7S,8S)‐9′‐(β‐rhamnopyranosyl)‐3‐methoxy‐3′:7,4′:8‐diepoxyneolignan‐4,9‐diol (4), together with eleven known compounds, cedral, sesquichamaenol, caryophylleneoxide, humulenepoxide, benzoic acid benzylester, 4‐hydroxy‐3‐methoxycinnamic acid, 7‐hydroxy‐8‐(3‐methylbut‐2‐enyl)chromen‐2‐one, 2‐[4‐(3‐ hydroxy propyl)‐2‐methoxyphenoxy]propane‐1,3‐diol, luteolin, 3,4‐bis‐(4‐hydroxy‐3‐methoxybenzyl)dihydro‐ furan‐2‐one, and pluviatolide were isolated from the leaves ofJu

ISSN:0009-4536    

DOI:10.1002/jccs.200100158

出版商:WILEY‐VCH Verlag    

年代:2001

数据来源: WILEY