Synthetische Juvenilhormone 1. Mitteilung. p-Substituierte β-Methyl-Zimtsäurederivate

In the first communication the synthetic methods are described for preparing aromatic analogues of juvenile hormone like activity. The para-substituted 2-methyl-cinnamic acid derivatives are formed by a Friedel-Crafts acylation of a phenol, followed by the Wadsworth-Emmons (Wittig-Horner)-Reaction with the corresponding phosphonates. More than 120 compounds are listed.     

Construction and Analysis of Lifson?Roig Models for the Helical Conformations of α‐Peptides

New forms of Lifson? Roig algorithms are introduced for modeling stabilities of helices formed by polypeptides derived from α‐amino acids. The principles of constructing and generalizing these algorithms are developed, and their application to modeling of circular dichroism ellipticities and protection factors derived from H/D exchange of α‐peptide backbone amide residues are critically reviewed. With the aim of comparing the properties of structured conformations formed by α‐ and β‐peptides, the intrinsic limitations of Lifson? Roig algorithms and their underlying assumptions are analyzed. Lifson? Roig state sums that provide easy structural analysis are generated by new algorithms based on products of 8×8 and 16×16 matrices, and a simple protocol is introduced for generating new state sums that are tailored for specific purposes. The N‐ and C‐capping of highly helical α‐peptides by means of tailored helix‐stabilizing templates is shown to result in helical conformational manifolds that approach those of helical β‐peptides in conformational homogeneity.     

Highly Conjugated Bis(benzo[b]phosphole)-P-oxides: Synthesis and Electrochemical,Optical, and Computational Studies

The first examples of a π-conjugated benzo[b]phosphole P-oxide in which two phosphole P-oxide units are connected by a carbon-carbon double bond are described. The molecules are synthesized as E isomers with respect to the carbon-carbon double bond and exist as stable cis and trans isomers (chiral and meso one respectively) relatively to the two stereogenic P atoms. The optical and electrochemical properties of both isomers have been investigated by experiment and computations.     

A systematic preparation of new contracted Gaussian-type orbital sets. IV. The effect of additional 3s functions introduced by the use of the six-membered 3dGTOs

The Gaussian-type basis sets for molecular calculations are usually prepared by an atomic SCF program in which spherical coordinates are used. On the other hand, many molecular SCF and CI programs are written by using the Cartesian coordinates and as a result six-membered d-type functions (x², y², z², xy, yz, zx)e^?γr2 are often used. They contain one additional 3s function which does not exist in the atomic calculation. Therefore, we shall have an incorrect, deeper molecular binding energy, unless we readjust the atomic total energy by adding the 3s orbital to the original basis set. Some examples are shown in the case of Cu₂ molecule, where we have found that the correction is quite appreciable, which was overlooked in previous work.     

An evaluation of the dyeing behavior of sol–gel silica doped with direct dyes

A new dyeing process of sol–gel silica doped with direct dyes is investigated for improving color strength (K/S value) and dyeing fastness. Cotton fabrics are dyed in this direct dye silica solution. The results indicate that the K/S value of C.I. Direct Blue 86 and C.I. Direct Red 23 are enhanced by 12.8% and 16.8%, respectively. For C.I. Direct Blue 86, the washing staining fastness is improved by half a grade, and the rubbing fastness and the washing change fastness are enhanced by one grade, respectively. Compared to the fabric fixed with fixing reagent MMF-1, the K/S value is improved by about 23.7% and the wet rubbing fastness and washing change fastness are enhanced by half a grade. The formation of uniform continuous layers on the fiber surface dyed with direct dye silica solution is revealed by video microscope, and the calculated sol–gel weight gain on the fabric is 4.6%.     

Electrochemical formation and composition analysis of Zn x Cd1-x Se solid solutions

The direct growth of ZnSe–CdSe solid solution onto metallic cathodes by electrodeposition from acidic aqueous sulphate solutions is described. The plating process is studied by simple voltammetry, while the structure and composition of the electrolytic deposits are investigated by X-ray diffraction. The experimental d-spacing values of the as-grown mixed lattice are compared to data from reference Zn _x Cd_1-x Se pellets of standard composition, produced by a sintering method. The findings are supplemented with energy-dispersive X-ray (EDX) elemental analysis. Thereupon, the variation of the mole fraction x in Zn _x Cd_1-x Se, and the solid phase constitution of the electrodeposits are determined and correlated to the electrochemical conditions of growth. The resulting films contain admixtures of CdSe compound and metallic Cd.     

Contracted polarization functions for B to Ar

Using optimal exponents for B through Ne given by Dunning and those for Al through Ar by Woon and Dunning, d-type contracted polarization functions (2d/1d), (3d/1d), and (3d/2d) are generated from natural orbitals of atomic single and double excitation configuration interaction (SDCI) calculations, where the numbers before and after the slash are those of the primitive and contracted Gaussian type functions. The resulting contracted functions are tested on N₂ and P₂ molecules by self-consistent field and SDCI calculations, which clarify characteristics of the present polarization functions. Received: 5 June 1997 / Accepted: 20 August 1997     

Plasma modification of polypropylene surfaces and grafting copolymerization of styrene onto polypropylene

The surface of polypropylene(iPP) is modified with glow discharge plasma of Ar,so that the modified surfaces of iPP films are obtained.The studies of scanning electron microscopy(SEM) show the surface etching pattern of iPP films. The chemical structures of iPP films are confirmed by X-ray photoelectron spectroscopy(XPS) and Fourier transform infrared(FTIR) spectroscopy.The wetting properties of modified surfaces of iPP films are characterized by contact angle, and the free energy of surfaces is calculated.The free radical of modification surfaces of iPP is measured by chemical method.The surfaces of iPP are achieved with Ar plasma treatment followed by grafting copolymerization with styrene(St) in St.The grafting polymer of St onto iPP is characterized by FTIR.The grafting rate is dependent on plasma exposure time and discharge voltage.The studies show that homopolymerization of St is undergone at the same time during the grafting-copolymerization of St onto iPP.     

Synthesis,Structure, and Antimalarial Activity of Some Enantiomerically Pure,cis-fused cyclopenteno-1,2,4-trioxanes

Two pairs of enantiomerically pure cis-fused cyclopenteno-1,2,4-trioxanes ( 7 , ent- 7 and 8 , ent- 8 ) are prepared (Schemes 1–3). Their identities are established by dye-sensitized photo-oxygenation of ent- 7 and 8 , ent- 8 to the allylichydroperxides, reduction to the corresponding alcohols, and conversion to the (1S)-camphanates (Scheme 4), the structures of which are determined by X-ray analysis. The dynamic properties of ent- 7 are investigated by NMR spectroscopy and PM3 calculations. Evidence for an easily accessible twist-boat conformation is obtained. The in vitro and in vivo antimalarial activities of 7 , ent- 7,8 , and ent- 8 as well as those of the racemic mixtures are evaluated against Plasmodium falciparum, P. berghei, and P. yoelii. No correlation is observed between configuration and activity. Racemates and pure enantiomers have commensurate activities. The mode of action on the intraerythrocytic parasite is rationalized in terms of close docking by the twist-boat conformer of the trioxane on the surface of a molecule of heme, single-electron transfer to the O? O σ* orbital, and scission to the acetal radical which then irreversibly isomerizes to a C-centered radical, the ultimate lethal agent (Scheme 5).     

Nucleophilic Reactions at Tertiary Carbon. Part 1. The 1,2-dimethyl-1-cyclohexyl cation

Stereoisomeric ion pairs are implicated as intermediates in the solvolysis of cis and trans-1-chloro-1,2-dimethylcyclohexane, cis- 4 and trans- 4 , respectively. This follows from the rates and products of these stereoisomeric tertiary chlorides in 80% ethanol and 50% acetone. The composition of elimination and substitution products from cis- 4 and trans- 4 differs markedly and the differences are accentuated by silver ion. Furthermore, substitution products are formed with predominant inversion of configuration. The equilibrium constant for isomerization of cis- 4 and trans- 4 shows the latter to be more stable by 0.7 kcal/mol. Since the solvolysis rates of the chlorides are equal, the transition state for trans- 4 is also more stable by 0.7 kcal. By inference the intermediates differ by a similar amount of energy which is ascribed to more efficient solvation of the trans ion pair 13 .     

Graphs to chemical structures. 4: Combinatorial enumeration of planted three-dimensional trees as stereochemical models of monosubstituted alkanes

Planted three-dimensional (3D) trees, which are defined as a 3D version of planted trees, are enumerated by means of Fujita’s proligand method formulated in Parts 1–3 of this series [Fujita in Theor Chem Acc 113:73–79, 80–86, 2005; Fujita in Theor Chem Acc 115:37–53, 2006]. By starting from the concepts of proligand and promolecule introduced previously [Fujita in Tetrahedron 47:31–46, 1991], a planted promolecule is defined as a 3D object in which the substitution positions of a given 3D skeleton are occupied by a root and proligands. Then, such planted promolecules are introduced as models of planted 3D-trees. Because each of the proligands in a given planted promolecule is regarded as another intermediate planted promolecule in a nested fashion, the given planted promolecule is recursively constructed by a set of such intermediates planted promolecules. The recursive nature of such intermediate planted promolecules is used to derive generating functions for enumerating planted promolecules or planted 3D-trees. The generating functions are based on cycle indices with chirality fittingness (CI-CFs), which are composed of three kinds of sphericity indices (SIs), i.e., a _d for homospheric cycles, c _d for enantiospheric cycles, and b _d for hemispheric cycles. For the purpose of evaluating c _d recursively, the concept of diploid is proposed, where the nested nature of c _d is demonstrated clearly. The SIs are applied to derive functional equations for recursive calculations, i.e., a(x), c(x ²), and b(x). Thereby, planted 3D-trees or equivalently monosubstituted alkanes as stereoisomers are enumerated recursively by counting planted promolecules. The resulting values are collected up to 20 carbon content in a tabular form. Now, the enumeration problem initiated by mathematician Cayley [Philos Mag 47(4):444–446, 1874] has been solved in such a systematic and integrated manner as satisfying both mathematical and chemical requirements.     

Stereochemical studies-XIV: Cyclic amino alcohols and related compounds-VII

1,3-Tetrahydro-oxazine-2-ones were prepared by the reaction of cis- and trans-2-hydroxymethylcyclohexylamine, as well as cis- and trans-2-aminomethylcyclohexanol with carbamide. Their structure and stereochemical purity were proved by IR and NMR investigations. With the help of the NMR spectra the conformation of these compounds was established. The trans isomers exist in stable chair-chair conformation. Two chair-chair conformations are possible in the case of the cis isomers; one in which the heteroatom and the methylene group of the heteroring are axial and equatorial, respectively and the second in which their positions are reversed. It was proved that the cis isomers are conformationally homogeneous, having the hetero atom in axial position.     

Synthesis of alkyl-5H-cyclopenta[b]pyrazines (author's transl)]

Synthesis of alkyl-5H-cyclopenta[b]pyrazines. Alkyl-5H-cyclopenta[b]-pyrazines (sometimes together with 5-alkylidene-5H-6,7-dihydrocyclopenta[b]pyrazines) are prepared by thermal degradation of 5-acetoxy-5H-6,7-dihydrocyclopenta[b]pyrazines; these are obtained by treatment of alkyl-5H-6,7-dihydrocyclopenta[b]pyrazine N-oxides with acetic anhydride. Cyclopenta[b]pyrazines which are potentially present in roasted food flavors possess interesting organoleptic properties.     

A New,General Synthetic Method for the Preparation of Linear Poly-p-xylylenes

A new, general synthetic route to poly-p-xylylene and substituted poly-p-xylylenes is described. The key intermediate in the new process is di-p-xylylene [(2,2)p-cyclophane]. It has been found that di-p-xylylene is quantitatively cleaved by vacuum vapor-phase pyrolysis at 600°C. to two molecules of p-xylylene. p-Xylylene spontaneously polymerizes on condensation to form high molecular weight, linear poly-p-xylylene. The conversion of di-p-xylylene to poly-p-xylylene is quantitative. The process is adaptable to the preparation of a wide variety of substituted poly-p-xylylenes by pyrolysis of ring-substituted di-p-xylylenes and polymerization of the resultant substituted p-xylylenes. Many of these polymers are not attainable by any other route. All are linear and free of crosslinking. Evidence supporting the proposed mechanism of pyrolytic cleavage of every molecule of di-p-xylylene to two molecules of p-xylylene is presented. Tough, transparent polymeric films are obtained from the process when the polymerization of the p-xylylenes is conducted on glass or metal surfaces. Outstanding combinations of physical, electrical, and chemical properties are displayed by poly-p-xylylene, polychloro-p-xylylene, and other substituted polymers. A comparison of the relative merits of the original Szwarc route and the new di-p-xylylene route to poly-p-xylylenes is presented.     

Microbial synthesis,physical properties,and biodegradability of polyhydroxyalkanoates

Poly((R)-3-hydroxybutyrate), P(3HB), is produced by Alcaligenes eutrophus from fructose or butyric acid. The kinetics and mechanism of P(3HB) biosynthesis are presented. Four types of copolymers, poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly (3-hydroxybutyrate-co-3-hydroxypropionate), poly (3-hydroxybutyrate-co-3-hydroxyhexanoate), and poly (3-hydroxybutyrate-co-4-hydroxybutyrate), are produced by several bacterial strains from various carbon substrates. These microbial polyesters are biodegradable thermoplastics whose physical properties can be regulated by varying the molecular structure and composition of copolymers.     

Net information measures for modified Yukawa and Hulthén potentials

The dimensional analyses of the position and momentum variances‐based quantum mechanical Heisenberg uncertainty measure, as well as the entropic information measures given by the Shannon information entropy sum and the product of Fisher information measures are carried out for two widely used nonrelativistic isotropic exponential‐cosine screened Coulomb potentials generated by multiplying the superpositions of (i) Yukawa‐like, ?Z(e^?μr/r), and (ii) Hulthén‐like, ?Zμ(1/(e^μr ? 1)), potentials by cos(bμr) followed by addition of the term a/r², where a and b ≥ 0, μ are the screening parameters and Z, in case of atoms, denotes the nuclear charge. Under the spherical symmetry, all the information measures considered are shown to be independent of the scaling of the set [μ, Z] at a fixed value of μ/Z, a, and b and the other parameters defining the superpositions of the potentials. Numerical results are presented, which support the validity of the scaling properties. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Structural studies of 3-chloro-N-(8′-quinolyl)×benzo[b]thiophene-2-carboxamide

3-Chloro-N-(8′-quinolyl)benzo[b]thiophene-2-carboxamide was synthesized from 3-chlorobenzo[b] thiophene -2-carboxyl chloride and 8-aminoquinoline in the presence of triethylamine. The single crystal X-ray structure determination confirmed the earlier proposed structure and also characterized by ¹HNMR, and Mass spectroscopy. Crystallographic study reveals that the structure crystallizes in monoclinic system, a = 14.878(4) ?, b = 8.4292(15) ?, c = 25.461(7) ?, β = 112.022(18)°, Z = 8, V = 2960.20(12) ?³ with space group C2/c (No. 15). In the structure packing, three kinds of interactions are responsible for the stability of the structure. Infinite two-dimensional stair-like layered chains are formed by relatively strong intermolecular hydrogen bonds [C14—H14...O1]. These parallel chains are connected by several π—π and CH—π interactions, alternatively. There are two such parallel chains with 70.53°, which are in contact by van der Waals interactions.     

Diastereoselective Synthesis of Nitroaldol Derivatives

Three methods are described by which diastereomerically enriched nitroaldols and their O-silylated derivatives can be prepared. threo-Nitroaldols prevail up to 10:1 over the erythro-isomers if doubly deprotonated nitroaldols 28 are quenched with acetic acid (THF/HMPT or DMPU, ? 100°) (see Scheme 5 and Table 2). O-Trimethyl- or O-(t-butyl)dimethylsilylated (TBDMSi) erythro-nitroaldols can be obtained by protonation of the corresponding lithium nitronates ( 35, 39 ) in THF at low temperature (see Schemes 6 and 7). The erythro-O-TBDMSi-nitroaldol derivatives are also formed in the fluoride catalyzed addition of TBDMSi-nitronates ( 40–45 ) to aldehydes (see Schemes 8 and 9), In the latter reaction no 1,2-asymmetric induction is observed if a-branched silylnitronates or aldehydes are employed (see 48/49 and 50/51 ) – The stereochemical course of the reactions leading to erythro-O-TBDMSi-nitroaldols follows topological rules of broad applicability (see Scheme 10); possible mechnisms are discussed. - The configuration of diasteromerically ¹³C-NMR. Spectroscopy. – Some examples of the preparation of diastereimerically enriched 1,2-aminolcohols by reduction of the correspondence nitro compounds without loss of configurational purity are described (see Schemes 11 and 12).     

Crystallization of poly(ethylene oxide) in binary polymer blends: Influence of tacticity of poly(methyl methacrylate)

Kinetics of the crystallization of poly(ethylene oxide) (PEO) from the PEO blends with syndiotactic, atactic, or isotactic poly(methyl methacrylate) (s-, a-, and i-PMMA) was investigated. The isothermal spherulitic growth rates were measured with an optical microscope. The influence of the composition of the blends, the tacticity of PMMA, and temperature on the growth rates were studied. Linear growth rates were observed regardless of the tacticity. The growth rates of spherulites are markedly reduced by a-PMMA and s-PMMA. However the growth rates of PEO are hardly influenced by i-PMMA. Such observations are interpreted by assuming that PEO forms miscible blends with a- and s-PMMA in the molten states, whereas it does not from with i-PMMA.