Metal-Assisted Crown Ethers for Evolutionary Design of Metal Hosts

The idea of metal-organization of linear molecules into macrocyclic structures is introduced. This idea has been tested on various oligoether compounds containing two chelate ligands at the terminals. Chelate ligands include -diketone, salicylic ester, catechol, and salicylic acid. The first two were organized into neutral metallocrown ethers, which showed much better extraction behavior towards alkali and alkaline earth metal cations than conventional monocyclic crown ethers. The last two were organized into ate-type complexes and incorporated metal ions into a newly formed anionic cavity. The stability constants were estimated for salicylate complexes and revealed excellent binding and selectivity. The presence of dipolar O--–Mn+ bonds in the metal organization method is concluded to contribute significantly to better interaction with metal ions through enthalpic stabilization.     

Photoinduced switch of a DNA/RNA inactive molecule into a classical intercalator

Spectroscopic titrations and thermal denaturation experiments show that "acyclic" analogue 1 does not bind to ds-DNA, but under same conditions "cyclic" 2 strongly interacts with ds-DNA and ds-RNA by intercalation into the double helix. Besides, 2 is significantly more effective in inhibition of the tumor cell growth in vitro than 1. We have shown that it is possible to efficiently and irreversibly convert "DNA inactive" compound 1 into "DNA active" compound 2 by light irradiation of the aqueous solutions of the former. This strategy offers a new and attractive approach to photoinduced anticancer therapy.     

Thermal Rearrangements of 3<Emphasis Type="Italic">H</Emphasis>- and 4<Emphasis Type="Italic">H</Emphasis>-Pyrazoles Prepared by Reactions of 9-Diazofluoren with Methyl Tetrolate and Methyl 3-Phenylpropiolate

9-Diazofluoren adds in Et₂O at 20°C to methyltetrolate in keeping with Auwers rule and nonregioselectively adds to methyl-3-phenylpropiolate with the formation of spirocyclic 3H-pyrazoles. The methyltetrolate adduct at boiling in toluene converts into methyl 3a-methyl-3aH-dibenzo[e,g]indazole-3-carboxylate, at 190°C in benzene, into methyl 3-methyl-2H-dibenzo[e,g]indazole-2-carboxylate, and at 160°C in methanol, into 3-methyl-2H-dibenzo[e,g]indazole. Auwers adduct of methyl 3-phenylpropiolate at boiling in benzene gives cyclopropene derivative and at boiling in methanol isomerizes into methyl 3a-phenyl-3aHdibenzo[e,g]indazole-3-carboxylate. Anti-Auwers adduct at boiling in benzene isomerizes into methyl 2-phenylpyrazolo[1,5-f]phenanthridine-3-carboxylate.     

Synthesis of the Eleutheside Core from (+)- Δ-Cadinol: Construction of Side Chains on the Menthane Ring

Methods for allylic oxygenation of (+)--cadinol by SeO₂ have been developed to study approaches to the formation of the eleutheside core from it. Diasteromeric alcohols and the product of their 1,4-oxacyclization, which is transformed into a bicyclic derivative containing the required functional groups to study the final cyclization into the eleutheside core, were prepared. The -hydroxy derivative was converted after benzylation and ozonolysis into a mixed acetal, a convenient compound for performing the synthesis via an alternate route.     

Self-organisation in the assembly of gels from mixtures of different dendritic peptide building blocks

This paper investigates dendritic peptides capable of assembling into nanostructured gels, and explores the effect on self-assembly of mixing different molecular building blocks. Thermal measurements, small angle X-ray scattering (SAXS) and circular dichroism (CD) spectroscopy are used to probe these materials on macroscopic, nanoscopic and molecular length scales. The results from these investigations demonstrate that in this case, systems with different "size" and "chirality" factors can self-organise, whilst systems with different "shape" factors cannot. The "size" and "chirality" factors are directly connected with the molecular information programmed into the dendritic peptides, whilst the shape factor depends on the group linking these peptides together--this is consistent with molecular recognition hydrogen bond pathways between the peptidic building blocks controlling the ability of these systems to self-recognise. These results demonstrate that mixtures of relatively complex peptides, with only subtle differences on the molecular scale, can self-organise into nanoscale structures, an important step in the spontaneous assembly of ordered systems from complex mixtures.     

Crystallochemical Aspect of Phase Formation in the γ-FeOOH-H2O-NaOH System

Phase transition of metastable -FeOOH into -FeOOH and its chemical transformation into -Fe₂O₃ upon hydrothermal treatment in 0-5 M NaOH solutions at 100-230°C were studied. The regions of formation of the above phases were specified. The probable composition of the crystallizing complexes formed in the solutions and the reactions occurring at their incorporation into various atomically smooth faces of -FeOOH and -Fe₂O₃ were considered.     

Intercalation of ferrocene and dimethylaminomethylferrocene into α-Sn(HPO4)2 · H2O and α-VOPO4 · 2H2O

The intercalation of ferrocene and dimethylaminomethylferrocene into -tin(IV) hydrogen phosphate (SnP) and -vanadyl phosphate has been investigated. Successful intercalation of 0.81 mol of dimethylamino-methylferrocene into -SnP by an acid-base reaction in aqueous medium to form a bilayer of protonated amines was achieved. However, ferrocene was not intercalated under the same conditions. Intercalation of -vanadyl phosphate by 0.11 mol of ferrocene in acetonic medium at room temperature was effected by a redox topotactic reaction. The voluminous dimethylaminomethylferrocene was not intercalated into -vanadyl phosphate.     

Oxidation of Cyclic Hemiacetals into Diketones: Final Steps in the Conversion of a Triterpenoid Ring a into a Steroidal Enone by a New Short Route

As a part of our studies in the conversion of triterpenoids into steroids we have reported¹ that the Jones oxidation of some triterpenoid hemiacetals (1) gives acyloxy acids (2) instead of the desired 1,5-diketones (3). We now report² the shortest route yet for the reconstruction of a triterpenoid ring A ketone (4) into a steroidal enone (7) involving as key steps the exhaustive Baeyer-Villiger oxidation³ of triterpenoid ketones (4) into δ-lactones (5) and mild chromium(VI) oxidation of cyclic hemiacetals (1) into diketones (3).     

Synthesis of 1-aryldihydro uracils and 1-aryl-2-thiodihydro uracils and their transformations

During the interaction of n-toluidine, n-anisidine, and n-phenetidine with methyl acrylate, the corresponding methyl esters of N-aryl--alanines and the corresponding N-aryl--alanines were obtained which were converted into 1-aryldihydro uracils and 1-aryl-2-thiodihydro uracils and then into 1-aryl-5-bromodehydrouracils, 1-aryl-2-thiohexahydropyrimidines, the hydrazides of N-aryl--alanines and 1-aryl-2-carboxymethylthio-4-oxo-1,4,5,6-tetrahydropyrimidines.     

Some reactions of 2-chloro-3-(β-chloroethyl)-4,6-dihydroxypyridine

The chemical properties of 2-chloro-3-(-chloroethyl)-4,6-dihydroxypyridine (I) have been studied. It has been shown that this compound, which is relatively stable in acids and in neutral and, particularly, in alkaline media, readily splits off hydrogen chloride under mild conditions and is converted into derivatives of 2, 3-dihydro-5-azabenzofuran. The dehalogenation of I in an acid medium yielded 3-(-chloroethyl)-4, 6-dihydroxypyridine, which was converted into 4, 6-dichloro-3-(-chloroethyl)pyridine and into 6-chloro-4-methoxy-3-vinylpyridine.     

An economic and efficient tetrahydrofuranylation of alcohols, imines and alkynes

The tetrahydrofuranyl radical, generated by heating tetrahydrofuran in the presence of air and allyl or benzyl chloride, becomes a useful tool in order to transform the hydroxyl functions into ethers, or the CN double bond into amine, or the C-C triple bond into vinyl derivatives. A radical mechanism is proposed followed by a nucleophilic substitution for the alcohol substrate and a radical addition for the iminic and the acetylenic reactants.     

Ethylα-fluoroacrylate in cycloaddition and diene synthesis reactions

Conclusions Ethyl-fluoroacrylate was introduced into the diene synthesis reaction with butadiene, isoprene, piperylene, and cyclopentadiene, and into the cycloaddition reaction with tetrafluoroethylene and trifluoro-chloroethylene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 358–362, February, 1971.     

Lead Tetraacetate Fragmentation of Loganin Aglucone O-Metheyl Ether and its Stereoisomers

During the investigation into methods of converting loganin (1) into secologanin (2, R=β-D-glucose), the lead tetraacetate fragmentation reaction¹ of the four diastereomeric loganin aglucone O-methyl ethers 4, 6, 9, and 11, was studied.     

基于路易斯结构式的含氧酸酸性半定量判定方法:1/2规则

基于经典价键理论中路易斯结构式建立了判定常见含氧酸酸性强弱的半定量方法“1/2规则”,并利用密度泛函理论验证了方法的可靠性和可行性。该方法可以用于判定常见含氧酸的强弱,同时解释多元酸的逐级电离过程、同种元素不同价态含氧酸酸性强弱变化规律等。该方法有助于学生掌握各类含氧酸酸性的判定规律,改变现有机械记忆的学习方法,引导学生形成“结构-能量-性质”的化学学科基本逻辑体系,提升学生的“宏观辨识与微观探析”化学学科核心素养。     

Student-Designed Experiment: Preparation and Mass Spectrum of Cyclohexasulfur

The teaching laboratory is an ideal environment for fostering active learning; yet, it is often criticized for being too cookbook. In introductory courses, the high student population often dictates that many students perform the same experiment simultaneously. By working in discussion groups, with individual bench work, we are able to turn this communal effort into a strength. This article describes the revision of a recipe-style experiment into a student-designed procedure.     

对“红铝”译名的异见

Red-Al是一种非常重要的铝基还原剂。国内学术界望文生义地将其直译为"红铝"是明显错误的。本文建议将其中文译名改为"还原铝"。     

Structural Changes in Loosening Amorphous Packings of Lennard-Jones Atoms

Computer simulations of crystalline and amorphous Lennard-Jones systems have revealed a stability threshold at reduced density 0.8-0.85. At this density, a substance undergoes a phase transition losing homogeneity and at lower densities decomposes into regions of dense atomic clusters separated by empty space. The characteristic size of atomic clusters is approximately 10 atomic diameters. They are united by bridges of close-packed atoms into a single percolation cluster. The voids form branched channels with diameters considerably exceeding an atomic diameter and permeating the entire space of the model.