Synthesis of (±)‐Kempa‐6,8‐dien‐3‐ol (=(2aRS,3SR,4aSR,7RS,7aSR,10bSR,10cSR)‐2,2a,3,4,4a,5,6,7,7a,8,10b,10c‐Dodecahydro‐2a,7,10,10c‐tetramethylnaphth[2,18‐cde]azulen‐3‐ol)

The synthesis of kempa‐6,8‐dien‐3β‐ol ( 4a ), as a synthetic leading model of the natural product 4b , was carried out starting from intermediate 12 , the synthetic route of which has been developed previously (Scheme 1). The conversion of 12 to the model compound 4a involved the elaboration of three structure modifications by three processes, Tasks A, B, and C (see Scheme 2). Task A was achieved by epoxy‐ring opening of 41 with Me₃SiCl (Scheme 9), and Task B being performed by oxidation at the 13‐position, followed by hydrogenation, and then epimerization (Schemes 4 and 5). The removal of the 2‐OH group from 12 (Task C) was achieved via 30b according to Scheme 6, whereby 30b was formed exclusively from 30a / 31a 1 : 1 (Scheme 7). In addition, some useful reactions from the synthetic viewpoint were developed during the course of the present experiments.     

Effect of carbon nanotubes on the crystallization and properties of polypropylene

The effect of different concentrations of single‐walled carbon nanotubes (SWNTs) on the nonisothermal crystallization kinetics, morphology, and mechanical properties of polypropylene (PP) matrix composites obtained by melt compounding was investigated by means of X‐ray diffraction, differential scanning calorimetry, optical and scanning electron microscopy, and dynamic mechanical thermal analysis. Microscopy showed well‐dispersed nanotube ropes together with small and large aggregates. The modulus was found to increase by about 75% at a level of 0.5 wt % nanotubes. The SWNTs displayed a clear nucleating effect on the PP crystallization, favoring the α crystalline form rather than the β form. The crystallization kinetics analysis showed a significant increase in activation energy on incorporating nanotubes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2445–2453, 2005     

Synthesis of 2‐Dihydrooxadiazolinyl Chromones

Reactions of the substituted 2‐formyl chromones with aroylhydrazines gave corresponding 2‐(aroylhydrazonomethylidyne) chromones. Then 2‐(3′‐acetyl‐5′‐aryl‐2′,3′‐dihydro‐1′,3′,4′‐oxadiazol‐2′‐yl) chromones were prepared by these 2‐(aroylhydrazonomethylidyne) chromones under refluxing with Ac₂O. All target compounds were characterized through elemental analysis and IR, ¹H NMR, MS.     

Decarbopalladation of pi-allylpalladium intermediates formed from palladium-catalyzed arylations of 3-allen-1-ols

[reaction: see text] Unusual palladium-catalyzed arylative fragmentations of acyclic 3-allen-1-ols were observed. Oxidative addition of Pd(0) to aryl halides would form the arylpalladium halides, which added to the central carbon of allenes via carbopalladation to form the pi-allylpalladium intermediates. The pi-allylpalladium intermediates would be reductively eliminated via carbon-carbon cleavage to give the arylated dienes and the alpha-hydroxyalkylpalladium intermediates, which were further reductively eliminated to the corresponding aldehydes.     

Polyterephthalamides with naphthoxy‐pendent groups

A series of new aromatic polyamides having pendent naphthoxy groups were synthesized by the triphenyl phosphite‐activated polycondensation of (2‐naphthoxy)terephthalic acid (NOTPA) with various aromatic diamines in a medium consisting of N‐methyl‐2‐pyrrolidone (NMP), pyridine, and calcium chloride. The diacid monomer NOTPA was prepared from the nitro displacement of dimethyl 2‐nitroterephthalate with the potassium naphthoxide of β‐naphthol, followed by base‐induced ester hydrolysis. All the resulting polymers were noncrystalline and readily soluble in aprotic polar solvents such as NMP and N,N‐dimethylacetamide. Almost all the polymers could be solution‐cast to tough, creasable amorphous films with good mechanical properties, the values of tensile strengths ranging from 90 to 124 MPa with initial moduli ranging from 1.72 to 2.51 GPa. Except for two examples, all the other polyamides displayed discernible glass transitions between 189 and 248 °C in the differential scanning calorimetric traces. These polyamides showed insignificant decomposition below 400 °C in nitrogen or air. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1781–1789, 2002     

Biomimetic Asymmetric Reduction of Quinazolinones with Chiral and Regenerable NAD(P)H Models

A facile approach to chiral dihydroquinazolinone derivatives has been described via biomimetic asymmetric reduction of quinazolinones with chiral and regenerable NAD(P)H models. The utility of this method was demonstrated by a concise synthesis of the bromodomain protein divalent inhibitor.     

Study on the Binding Effect between Cordycepin and Calf Thymus DNA by Circular Dichroism

DNA works as hereditary material and plays vital role in life science. The study of the binding of small molecules complex to DNA has been the focus of intense investigation, owning to their stereo and sequence specific interaction with the double helix1-…     

Synthesis and Antimicrobial Activity of New Pyridothienopyrimidines and Pyridothienotriazines

5‐Acetyl‐3‐amino‐4‐aryl‐6‐methylthieno[2,3‐b]pyridine‐2‐carboxamides ( 5a,b ) were reacted with triethyl orthoformate or nitrous acid to give the corresponding pyrimidinones 6a,b and triazinones 7a,b . The reaction of 5a,b with acetic anhydride was carried out and its products were identified as a mixture of 8‐acetyl‐9‐aryl‐2,7‐dimethylpyrido[3′,2′:4,5]thieno[3,2‐d]pyrimidine‐4(3H)‐one ( 9a,b ) and related 5‐acetyl‐4‐aryl‐3‐biacetylamino‐6‐methylthieno[2,3‐b]pyridine‐2‐carbonitrile ( 10a,b ). Reaction of 7a with some halocompounds afforded the N‐alkylated triazinones 8a‐c . Chlorination of 6a,b and 9a,b with phosphorus oxychloride produced 4‐chloropyrimidines 11a‐d which were used as precursors for the rest of the target heterocycles. Some of the prepared compounds were tested in vitro for their antimicrobial activities.     

Different reaction routes found in acid-catalyzed glycosylation of endo- and exo-glycals: competition between Ferrier rearrangement and protonation

Acid-mediated glycosylations of endo- and exo-glycals have been carried out in good to excellent yields, in which a mixture of two products is often obtained resulting from Ferrier rearrangement and protonation. The former reaction exclusively takes place with the t-butyl carbonate or hydroxyl substituent at the C3 position of endo-glycals, while the latter mainly occurs in the glycosylation of exo-glycals with allyl benzyl ether or acetate. In addition to the substituent effect, protecting groups are critical to determine the activity and favored reaction pathway. Furthermore, the method is applicable to O-, C-, and N-nucleophiles.     

Simultaneous Determination of Glyphosate,Glufosinate, and Aminomethylphosphonic Acid by Capillary Electrophoresis After 9‐Fluorenylmethyl Chloroformate Derivatization

A capillary electrophoresis (CE) with UV absorption detection method is described for the simultaneous determination of glufosinate, glyphosate, and aminomethylphosphoric acid. The 9‐fluorenylmethyl chloroformate (FMOC‐Cl) was used for precolumn derivatization of the non‐absorbing herbicides. The three analytes were separated by CE in 9 min with 25 mM borate buffer at pH 9, followed by detection with a UV detector at 260 nm. We demonstrate how the detection limit can be enhanced by using acetonitrile‐salt mixtures. With acetonitrile‐salt mixtures, the limit of detection (LOD) was in the 10^?7 M range. Linearity of more than two orders of magnitude was generally obtained. Precisions of migration times and peak areas were less than 0.9% and 7.5%, respectively. The applicabilities of the method for the analysis of ground water and lake water were examined.