Photoreduction of an α-Dichloroketone

We describe here a simple three step synthesis of B-santalene (1), one of the main hydrocarbons in East Indian Sandalwood oil,³ using the readily available camphene sultone (2) as a starting material. This synthesis, outlined in Figure 1, features the novel use of a sultone as a carbon activating group and involves a new desulfurization procechrre.     

Cellular uptake of an α-AApeptide

Some short and cationic peptides such as the Tat peptide can cross the cell membrane and function as vectors for intracellular delivery. Here we show that an α-AApeptide is able to penetrate the membranes of living cells from an extracellular environment and enter the endosome and cytoplasm of cells. The efficiency of the cellular uptake is comparable to a Tat peptide (48-57) of the same length and is unexpectedly superior to an α-peptide with identical functional groups. The mechanism of uptake is similar to that of the Tat peptide and is through endocytosis by an energy-dependent pathway. Due to the easy synthesis of the α-AApeptides, their resistance to proteolytic hydrolysis, and their low cytotoxicity, α-AApeptides represent a new class of transporters for the delivery of drugs.     

Synthesis and Antitumor Activity of an Analog of Phthalascidin

Ecteinascidin 743 (Et-743) is an exceedingly potent antitumor agent isolated from the extracts of the marine tunicate Ecteinascidia turbinate1 that is currently undergoing phase Ⅱ/Ⅲ clinical trials in Europe and the United States2. As the result of its …     

Diarylprolinol in an asymmetric aldol reaction of an α-alkyl-α-oxo aldehyde as an electrophile

The direct aldol reaction of an α-alkyl-α-oxo aldehyde was catalyzed by trifluoromethyl-substituted diarylprolinol 1 to afford a γ-oxo-β-hydroxy-α-substituted aldehyde in good yield with excellent anti-selectivity and excellent enantioselectivity.     

Intermolecular Interaction of HMX： an Application of ONIOM Methodology

IntroductionExtensive studies on intermolecular interac-tions have been made in the past decades due totheir importance in a wide range of physical,chem-ical and biological fields.Researches on the weakintermolecular interactions began with hydrogenbonds.Scheiner summarized the ab initio investiga-tions on hydrogen bonding in detail[1] .With the abinitio method supermolecular structures and bind-ing energies can be predicted notonly for H- bondedsystems but also for other systems[2 _ 5] when …     

A Special Property of DNA--as an Electrocatalyst

TheinvestigationofinteractionofDNA(deoxyribonucleicacid)withothermolecules1-8isofgreatimportanceinelucidatingthestYUctUresofDNAandtheirfunction.Also,itishelpfultounderstandingsomediseasesandthemechanismsbywhichsomemedicines(especiallyantitumordrugs)act.Currently,DNA-modifiedelectrodesareusedtostUdytheinteractionpropertyofDNAwithothermoleculessuchasdrugs,proteins,etc.3'4'6-8.Powdermicroelectrode(PME)icisanewtypeofporouselectrodeeasytoprepare,whichissuitableforthestudyofelectrocatalytica…     

Electropolymerization of O-Phenylenediamine in an Ionic Liquid

Ionic liquid like 1-ethyl-3-methylimidazolium bromine ([EMIM]Br) has been used as electrolyte for the electropolymerization of O-phenylenediamine at glassy carbon electrode by cyclic voltammetry. It is found that poly (O-phenylenediamine) film modified electrode has favorable electrochemical activity in acid solution.     

Dielectric spectroscopy of an antiferroelectric liquid crystal showing an antiferroelectric–ferrielectric transition

We report the dielectric relaxation behaviour in the antiferroelectric SmC_A* and ferrielectric SmC_γ* phases of the antiferroelectric liquid crystal 4-[5-(4-octloxyphenyl)-2-pyrimidinyl]phenyl 4,4,4-trifluoro-3-(methoxyphenyl)butanoate which shows an antiferroelectric transition at around 88±0.1°C. In the SmC_A* phase, two dielectric relaxation modes have been found, namely the usual antiferroelectric Goldstone mode and another arising from molecular rotation around its short axis. In the SmC_γ* phase, one dielectric relaxation mode has been observed due to the ferrielectric Goldstone mode. Dielectric increments and relaxation frequencies of the antiferroelectric and ferrielectric phases are estimated from the fits of the Cole–Cole function of the dielectric spectrum. The dependence of the bias field in the ferrielectric phase is also discussed.     

Reaction of arylhydrazines with an α-alkynyl-carbonylic compound: an unexpected hydration reaction

The acid catalyzed reactions of three arylhydrazines with 4-phenyl-3-butynone in order to obtain the corresponding arylhydrazone were realized. The arylhydrazone reaction and an unexpected alkyne hydration reaction product were obtained when diphenylhydrazine was used. This product was identified by spectroscopic methods and X-ray diffractogram. A reaction mechanism is proposed for its formation.     

Reversal of regiocontrol in the alkylation of an arene π-complex

Tricarbonyl(η⁶-1-methoxy-2,4-dimethylbenzene)manganese(1+) hexafluorophosphate(1−) was preferentially alkylated by vinyl Grignard reagents at C(5), When methymagnesium bromide was used, however, reaction occurred predominantly at C(3), the more hindered of the two sites meta to the methoxy substituent.     

Synthesis of an Acyloxymethyl Prodrug of the Inositol Phosphate α-Trinositol

ABSTRACT

Acyloxymethylation of an acylated silver salt of α-trinositol gives, after deprotection, membrane permeable 1D-myo-inositol 1,2,6-tris(ethoxycarbonyloxymethyl sodium phosphate). The acyl groups, 3-(4,5-methylenedioxy-2-nitrophenyl)propanoyl, are cleaved by hydrogenolysis.     

Electrochemical Synthesis of Polythiophene in an Ionic Liquid

Polythiophene(PTh) was prepared by the direct electrochemical synthesis in an ionic liquid ([BMIM]PF6) containing 0.1mol/L thiophene by cyclic voltammetry,constant potential and constant current techniques. It is found that smooth and blue-green PTh films can be obtained at a potential of ca. 1.75V(vs. Ag/AgCl) or a current of ca. 1.5mA cm^-2 in the ionic liquid.     

Chemoenzymatic synthesis of an α-substituted serine derivative

An asymmetric synthesis of an α-substituted serine derivative was achieved by employing PLE-catalyzed hydrolysis of a prochiral malonate derivative, and the absolute configuration of the hydrolyzed product was unambiguously determined by the X-ray analysis of a camphorsulfonic acid derivative.     

Chiral Synthesis of an α-Tetrasubstituted Proline Derivative

An efficient approach for the synthesis of a new class of triazolophanes by 1,3-dipolar cycloaddition reaction of highly reactive organic azides with dialkynes using Cu(I)-catalyzed azide–alkyne cycloaddition methodology (“click chemistry”) has been developed. All the compounds were characterized by spectral and elemental analyses.     

NMR Microscopy of an “Anisotropic” Polymer

Two different samples of high-density polyethylene (HDPE) have been studied. One (isotropic) is extracted from the material core whereas the other (anisotropic) involves two sides which have been in contact with the injection mold. It is observed by NMR microscopy (using radiofrequency field gradients) that these two sides favor toluene penetration into the material. The distribution of toluene nuclear spin relaxation times (extracted from proton T₁ and T₂ images) exhibits likewise important differences between the two samples. These differences can be accounted for by partial molecular ordering at the vicinity of the “mold sides”. Finally, in investigating the anisotropic sample (without solvent), three different phases (two amorphous and one crystalline) are revealed by ¹³C chemical shift imaging experiments (performed with radiofrequency field gradients under CP/MAS conditions). Each amorphous component is preferentially present at one of the two “mold sides”.     

Kinetic Analysis of an Enzyme-containing Polymer Modified Electrode

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Synthesis of an Enkephalin Analogue Containing an α,α-Disubstituted Heterocyclic Aminophosphonic Acid

Abstract

Synthesis of a phosphonopentapeptide enkephalin analogue was achieved from heterocyclic aminophosphonates via the coupling of Boc-Tyr-Gly-Gly-OH with phosphonodipeptide. The latter was formed by coupling Boc-Phe-OH with N-terminal α,α-disubstituted heterocyclic α-aminophosphonates.

GRAPHICAL ABSTRACT      

First Total Synthesis of an Analogue of (±)-Hypargenin B

Hypargenin B, a diterpene with the abietane skeleton, was isolated by Ayhan from the root of an endemic species salvia hypargenia and showed antibacterial activity1. In this diterpene, the junction of A/B ring is trans. In order to provide for studying further the relationship between the structure and bioactivities, we develop a novel route whereby the hypargenin B methyl ether 22 could be obtained in good yield. To our knowledge no total synthetic work has been reported on the title com…     

Synthesis of an Analogue of Squalamine： 6β-Hydroxyl-3-aminosterol

6β-Hydroxylsqualamine was synthesized stereoselectively in 13 steps and 19% overall yield from methyl hyodeoxycholanate by using stereospecific epoxidation and asymmetric isopropylation as key steps.     

Photochemistry of α-phenoxyacetophenone: an interesting case of intramolecular triplet deactivation

α-Phenoxyacetophenone undergoes efficient intramolecular triplet deactivation involving quenching by the β-phenyl ring. The process is about an order of magnitude faster than in the case of the all-carbon analogue β-phenylpropiophenone. The difference in the rates of intramolecular quenching is attributed to a reduction of the hydrogen eclipsing interactions in the case of the heteroatom-containing backbone. α-Phenoxyacetophenone photodecomposes with a quantum yield of about 0.004 to yield C₆H₅COCH₂ and C₆H₅O^.; in spite of its low quantum yield the process is quite rapid, occurring with an estimated rate constant of 3 × 10⁷ s⁻¹.