Synthesis of Optically Active P‐Chiral and Optically Inactive Oligophosphines

A series of optically active P‐chiral oligophosphines (S,R,R,S)‐ 2 , (S,R,S,S,R,S)‐ 3 , (S,R,S,R,R,S,R,S)‐ 4 , and (S,R,S,R,S,R,R,S,R,S,R,S)‐ 5 with four, six, eight, and 12 chiral phosphorus atoms, respectively, were successfully synthesized by a step‐by‐step oxidative‐coupling reaction from (S,S)‐ 1 . The corresponding optically inactive oligophosphines 1′ – 5′ were also prepared. Their properties were characterized by DSC, XRD, and optical‐rotation analyses. While optically active bisphosphine (S,S)‐ 1 and tetraphosphine (S,R,R,S)‐ 2 behaved as small molecules, octaphosphine (S,R,S,R,R,S,R,S)‐ 4 and dodecaphosphine (S,R,S,R,S,R,R,S,R,S,R,S)‐ 5 exhibited the features of a polymer. Furthermore, DSC and XRD analyses showed that hexaphosphine (S,R,S,S,R,S)‐ 3 is an intermediate between a small molecule and a polymer. Comparison of optically active oligophosphines 1 – 5 with the corresponding optically inactive oligophosphines 1′ – 5′ revealed that the optically active phosphines have higher crystallinity than the optically inactive counterparts. It is considered that the properties of oligophosphines depend on the enantiomeric purity as well as the oligomer chain length.     

Synthesis, π‐Face‐Selective Aggregation,and π‐Face Chiral Recognition of Configurationally Stable C3‐Symmetric Propeller‐Chiral Molecules with a π‐Core

The C₃‐symmetric propeller‐chiral compounds (P,P,P)‐ 1 and (M,M,M)‐ 1 with planar π‐cores perpendicular to the C₃‐axis were synthesized in optically pure states. (P,P,P)‐ 1 possesses two distinguishable propeller‐chiral π‐faces with rims of different heights named the (P/L)‐face and (P/H)‐face. Each face is configurationally stable because of the rigid structure of the helicenes contained in the π‐core. (P,P,P)‐ 1 formed dimeric aggregates in organic solutions as indicated by the results of ¹H NMR, CD, and UV/Vis spectroscopy and vapor pressure osmometry analyses. The (P/L)/(P/L) interactions were observed in the solid state by single‐crystal X‐ray analysis, and they were also predominant over the (P/H)/(P/H) and (P/L)/(P/H) interactions in solution, as indicated by the results of ¹H and 2D NMR spectroscopy analyses. The dimerization constant was obtained for a racemic mixture, which showed that the heterochiral (P,P,P)‐ 1 /(M,M,M)‐ 1 interactions were much weaker than the homochiral (P,P,P)‐ 1 /(P,P,P)‐ 1 interactions. The results indicated that the propeller‐chiral (P/L)‐face interacts with the (P/L)‐face more strongly than with the (P/H)‐face, (M/L)‐face, and (M/H)‐face. The study showed the π‐face‐selective aggregation and π‐face chiral recognition of the configurationally stable propeller‐chiral molecules.     

Synthesis of Phenyl- and Benzyl-Substituted Pyrrolidines and of a Piperidine by Intramolecular C-Alkylation. Synthons for tricyclic skeletons

The construction of new or novelly functionalized annulated and bridged tricylic compounds by two consecutive C,C-bond formations (a and b in la , Scheme 1) is described. In a first step, chloroalkyl-substituted aminonitriles yielded pyrrolidines 8 , 15a , 15b , 23 , 25 and piperidine 18 by carbanionic ring closure (Schemes 5, 6, 7 and 8). Subsequent Friedel-Crafts cyclization transformed the β-aminonitriles 8 , 15a , 15b , and 18 either directly or via their carboxylic acid derivatives to the indeno [1, 2-c]pyrrole, 2, 5-methano-3-benzazocine, benz [f]isoindoline and 1, 4-ethano-2-benzazapine skeletons 11 , 16a , 16b and 21 , respectively (Schemes 5, 6 and 7). By classical ring expansion reactions the pyrrolo [3, 4-c]isoquinoline and benzopyrano-[3, 4-c]pyrrole skeletons 28 resp. 31 were obtained from 11 (Scheme 9).     

Helical silica nanotubes: Nanofabrication architecture,transfer of helix and chirality to silica nanotubes

A series of neutral gelators and cationic amphiphiles derived from 1,2 diphenylethylenediamine (I) and 1,2-cyclohexanediamine (II) was synthesised. Helical silica nanotubes were prepared utilising these organic gelators through sol-gel polycondensation of tetraethoxy silane, (TEOS-silica source). Right- and left-handed helical nanotubes respectively were obtained from a 1: 1 mass mixture of optically active, (1S,2S)-III-(1S,2S)-V neutral gelator and (1S,2S)-IV-(1S,2S)-VI cationic amphiphile and a 1: 1 mass mixture of optically active, (1R,2R)-III-(1R,2R)-V neutral gelator and (1R,2R)-IV-(1R,2R)-VI cationic amphiphile, indicating that the handedness of the helical nanotubes varied with the change in the neutral gelator precursors used. The nanotubes were characterised by SEM images.     

Hydrostannylation of phosphaalkenes [1]

Hydrostannylation reactions of the phosphaalkenes 9,11, and 21 with the triorganotin hydrides 1 proceed by different routes. Whereas the trior-ganotin hydrides 1a,b undergo regioselective 1,2-addition to the P/C double bond of the P-aminophosphaalkene 9 to furnish the 2-stannylphosphanes 17a,b, the 1,2-addition products to the P-halophosphaalkenes 11 and 21 can only be postulated as the reactive intermediates 20 and 23, respectively. The reactions of 11 with 1a,b proceed with cleavage of the triorganotin halide via the diphosphene 15 to furnish the cyclophosphanes 18 and 19. On the other hand, the hydrostannylation reactions of the phosphaalkene 21 are not selective, and the 1,3-diphosphetane 22 is isolated as one of the reaction products. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:453–460, 1998     

Biodegradation of Polyhydroxyalkanoate Films in Natural Environments

Summary: Biodegradation of film specimens from polyhydroxyalkanoates (PHAs) of two types – poly-3-hydroxybutyrate (PHB) and poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) – was analysed in different environments: tropical sea waters of the South China Sea (Nha Trang, Vietnam) and soils in the environs of Hanoi (Vietnam), Nha Trang (Vietnam) and Krasnoyarsk (Siberia, Russia). In seawater, the mass loss of the specimens of both types was almost equal. However, in tropical soils, PHB degraded quicker than PHBV. In the Siberian soil, the degradation rate of the PHBV was generally higher than that of PHBV. Analysis of molecular mass of PHA specimens showed its decreasing during biodegradation. In the tropical sea conditions, PHA degrading microorganisms were represented by bacteria of Enterobacter, Bacillus and Gracilibacillus genera. Among PHA degrading bacteria, Burkholderia, Alcaligenes, Bacillus, Mycobacterium and Streptomyces genera were identified in Vietnamese soils, and Variovorax, Stenotrophomonas, Acinetobacter, Pseudomonas, Bacillus and Xanthomonas genera in Siberian soils. Micromycetes of Gongronella, Paecilomyces, Penicillium and Trichoderma genera exhibited PHA degrading activity in Vietnamese soils, and Paecilomyces, Penicillium, Acremonium, Verticillium and Zygosporium genera – in Siberian soils.     

A convenient and diastereoselective route to homoallyl alcohols: Addition of (z)- or (e)-alkenyl-dimethoxyboranes to aldehydes

(Z)-2-Butenyl-dimethoxyborane adds smoothly to propanal and benzaldehyde to afford the homoallyl alcohols (R*,R*)- 1 and (R*,R*)- 2 , In contrast (E)-2-butenyl-dimethoxyborane leads to adducts having the (R*,S*)-configuration. Dimethoxy-(Z)-2-pentenylborane, dimethoxy-(Z)-(2-methyl-2-butenyl)borane and (2Z,4E)-or (2E,4Z)hexadienyl-dimethoxyborane, treated with propanal, give (R*,R*)- 3 , (R*,R*)- 4 , (E),(R*,S*)- 5 and (Z),(R*, R*)- 5 , respectively. A transition state model implying a pericyclic electron motion is in perfect agreement with the regio- and stereoselective outcome of these borane reactions.     

Derivatives Of ditraizinylamine and tritriazinylamine

2-Arylamino-4,6-dichloro-s-triazine reacts with cyanuric chloride in the presence of alkali to yield N,N-bis(4,6-dichloro-s-triazin-2-yl)-arylamine. In like manner, 2-substituted o-chloro-, p-chloro-, o-nitro- and p-carbomethoxyphenylamino-4,6-dimethoxy-s-triazines react with cyanuric chloride to yield the corresponding 4,6-dichloro-s-triazin-2-yl-4′,6′-dimethoxy-s-triazin-2′-ylaryl-amine, while anilino-, p-toluidino, o- and p-methoxyphenylamino and o-carbomethoxyphenylamino derivatives did not. The reaction of cyanuric chloride with 2,4-dichloro-6-ethylamino-s-triazine in the presence of alkali yields the condensation product of the ditriazinylamine type and the reaction of cyanuric chloride with ammonia yields N,N-bis(4,6-dichloro-s-triazin-2-yl)- or tris(4,6-dichloro-s-triazin-2-yl)amine.     

Order parameter studies from effective order geometry in 4O.Om and 7O.Om liquid crystalline compounds

The effective geometry parameter, α_g = n _o /n _e, is used to evaluate the orientational order parameter, S, in the case of N-(p-n-butyloxybenzylidene)-p-n-alkoxy anilines, 4O.Om and N-(p-n-heptyloxybenzylidene)-p-n-alkoxy anilines, 7O.Om compounds with m?=?3–7 and 9 in the former case and m?=?3, 5–7 and 9 in the later materials. The results obtained are compared with those calculated using the standard techniques of molecular polarisability and birefringence. The effective geometry parameter's influence on the deflection of light by the liquid crystal compounds is also studied. The variation of temperature gradient of the ordinary refractive index, dn _o /dT, and extraordinary refractive index, dn _e /dT, of the liquid crystals is also studied.     

Relating Total π-Electron Energy and Resonance Energy of Benzenoid Molecules with Kekulé- and Clar-Structure-Based Parameters

Within classes of isomeric benzenoid hydrocarbons various Kekulé- and Clar-structure-based parameters (Kekulé structure count, Clar cover count, Herndon number, Zhang–Zhang polynomial) are all mutually correlated. This explains why both the total π-electron energy (E), the Dewar resonance energy (DRE), and the topological resonance energy (TRE) are well correlated with all these parameters. Nevertheless, there exists an optimal value of the variable of the Zhang–Zhang polynomial for which it yields the best results. This optimal value is negative-valued for E, around zero for TRE, and positive-valued for DRE. A somewhat surprising result is that TRE and DRE considerably differ in their dependence on Kekulé- and Clar-structure-based parameters.     

Kinetics and Protein‐Inhibitor Docking Studies of Enantiomers of exo‐2‐Norbornyl‐N‐n‐butylcarbamates as Pseudomonas Lipase Inhibitors to Probe the Enantioselectivity of the Enzyme

The Pseudomonas species lipase inhibition shows enantioselectivity for R‐enantiomer over S‐enantiomer of exo‐2‐norbornyl‐N‐n‐butylcarbamates. R‐, S‐, and racemic‐exo‐2‐norbornyl‐N‐n‐butylcarbamates are all characterized as pseudo substrate inhibitors of the enzyme. Thus, the mechanism for Pseudomonas species lipase‐catalyzed hydrolysis of the inhibitor is formation of the first enzyme‐inhibitor Michaelis complex via nucleophilic attack of the active site serine to the inhibitor (K_i step) then formation of the butylcarbamyl enzyme intermediate from this complex (k₂ step). Comparison of bimolecular rate constants (k_i = k₂ / K_i) of the inhibitors indicates that R‐enantiomer is 1.8 times more potent than S‐enantiomer. Thus, Pseudomonas species lipase shows enantioselectivity of 1.8 for R‐exo‐2‐norbornyl‐N‐n‐butyl‐carbamate over S‐exo‐2‐norbornyl‐N‐n‐butylcarbamate. Protein‐ligand interaction studies on both enantiomers of exo‐2‐norbornyl‐N‐n‐butylcarbamate as inhibitors of Pseudomonas species lipase using AutoDock suggest that R‐enantiomer binds more tightly into the active site of the enzyme than S‐enantiomer. The norbornyl ring of S‐exo‐2‐norbornyl‐N‐n‐butylcarbamate is repulsive to Ser 82 and His 251 of the catalytic triad as well as to Met 16 of the oxyanion hole. These repulsions may create few unfavorable interactions between S‐exo‐2‐norbornyl‐N‐n‐butylcarbamate and the enzyme and make this inhibitor a less potent one.     

Hosoya polynomials of TUC4C8(R) nanotubes

For a connected graph G, the Hosoya polynomial of G is defined as H(G, x) = ∑_{u,v}?V(G)x^{d(u, v)}, where V(G) is the set of all vertices of G and d(u,v) is the distance between vertices u and v. In this article, we obtain analytical expressions for Hosoya polynomials of TUC₄C₈(R) nanotubes. Furthermore, the Wiener index and the hyper‐Wiener index can be calculated. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

Theory of polydisperse reacting polymer systems

The kinetics of irreversible reactions between polymer chains of different molecular weights are studied, with emphasis on the case of highly reactive end groups. We calculate the rate constant k(N, M) for reaction between chains of lengths N and M respectively, in dilute and semi-dilute solutions and in the melt. In all cases, k(N, M) is dominated by the shortest chain: the limit k(N) ≡ k(N, ∞) is well-defined and scales as if both chains were of length N. In dilute solutions k(N, M) obeys mean field theory, being proportional to the equilibrium reactive group contact probability. For melts and concentrated solutions, k(N, M) follows diffusion-controlled laws: k(N, M) ≈ (R/τ_N)ƒ(M/N) where R_N and τ_N are the coil size and relaxation time of the shortest chain N, and ƒ(M/N) is a cross-over function describing the approach to the asymptotic form k(N) for M/N ≫ 1. We calculate the leading contributions to this cross-over function, which has universal forms depending on the concentration regime. The implications of these results for high-conversion free-radical polymerization are discussed.     

On molecular topological properties of hex‐derived networks

Topological indices are numerical parameters of a molecular graph, which characterize its topology and are usually graph invariant. In quantitative structure–activity relationship/quantitative structure–property relationship study, physico‐chemical properties and topological indices such as Randić, atom–bond connectivity (ABC), and geometric–arithmetic (GA) index are used to predict the bioactivity of chemical compounds. Graph theory has found a considerable use in this area of research. In this paper, we study hex‐derived networks HDN1(n) and HDN2(n), which are generated by hexagonal network of dimension n and derive analytical closed results of general Randić index R_α(G) for different values of α, for these networks of dimension n. We also compute the general first Zagreb, ABC, GA, ABC₄, and GA₅ indices for these hex‐derived networks for the first time and give closed formulae of these degree‐based indices for hex‐derived networks. Copyright © 2016 John Wiley & Sons, Ltd.     

Theoretical and experimental studies of the electrochemistry of <Emphasis Type="Italic">p</Emphasis>-aminophenol on a golden electrode

The geometric parameters, vibrational frequencies, and thermochemical values of p-quinonimine (p-AQ) and p-aminophenol (p-AP) were computed ab initio (IIF) and by the density functional theory (DFT) method with the 6-31G(d, p) basis set. Cyclic voltammetry with a golden electrode of p-AP solutions in phosphate buffers at pH 7.30 showed that the standard electrode potential of half reaction for p-QI and p-AP was 0.728 V. The standard electrode potentials of half reactions for p-QI and p-AP were calculated using the free energies and solvation energies of p-QI, p-AP, p-benzoquinone (p-BQ), and hydroquinone (p-HQ). The results showed that the standard electrode potential of half reaction for p-QI and p-AP was 0.743 V at the B3LYP/6-31G(d, p) level and 0.755 V at the HF/6-31G(d, p) level. The standard electrode potentials computed at the B3LYP/6-31G(d, p) and HF/6-31G(d, p) levels were close to their experimental values. The article is published in the original.     

Spectroscopic and magnetic properties of Cu(II) complexes with selected biologically important ligands

The aim of this work was to study the spectroscopic and magnetic properties of copper(II) o-, m-, p-aminobenzoates, o-, m-, p-methoxybenzoates and o-, m- and p-nitrobenzoates. The complexes were synthesized and their compositions were evaluated by elementary analysis. The infrared and Raman spectra for Cu(II) aminobenzoates, methoxybenzoates and nitrobenzoates were recorded and assigned. The obtained data were compared with those previously published for aminobenzoic, methoxybenzoic and nitrobenzoic acids and their sodium salts. The structures of Cu(II) o-, m-, p-aminobenzoates, o-, m-, p-methoxybenzoates and o-, m- and p-nitrobenzoates as well as the change in the electronic charges distribution caused by Cu(II) complex formation were discussed.     

Molecular Recognition of Pyranosides by a Family of Trimeric, 1,1′-Binaphthalene-Derived Cyclophane Receptors

The synthesis and carbohydrate-recognition properties of a new family of optically active cyclophane receptors, 1 – 3 , in which three 1,1′-binaphthalene-2,2′-diol spacers are interconnected by three buta-1,3-diynediyl linkers, are described. The macrocycles all contain highly preorganized cavities lined with six convergent OH groups for H-bonding and complementary in size and shape to monosaccharides. Compounds 1 – 3 differ by the functionality attached to the major groove of the 1,1′-binaphthalene-2,2′-diol spacers. The major grooves of the spacers in 2 are unsubstituted, whereas those in 1 bear benzyloxy (BnO) groups in the 7,7′-positions and those in 3 2-phenylethyl groups in the 6,6′-positions. The preparation of the more planar, D₃-symmetrical receptors (R,R,R)- 1 (Schemes 1 and 2), (S,S,S)- 1 (Scheme 4), (S,S,S)- 2 (Scheme 5), and (S,S,S)- 3 (Scheme 8) involved as key step the Glaser-Hay cyclotrimerization of the corresponding OH-protected 3,3′-diethynyl-1,1′-binaphthalene-2,2′-diol precursors, which yielded tetrameric and pentameric macrocycles in addition to the desired trimeric compounds. The synthesis of the less planar, C₂-symmetrical receptors (R,R,S)- 2 (Scheme 6) and (S,S,R)- 3 (Scheme 9) proceeded via two Glaser-Hay coupling steps. First, two monomeric precursors of identical configuration were oxidatively coupled to give a dimeric intermediate which was then subjected to macrocyclization with a third monomeric 1,1′-binaphthalene precursor of opposite configuration. The 3,3′-dialkynylation of the OH-protected 1,1′-binaphthalene-2,2′-diol precursors for the macrocyclizations was either performed by Stille (Scheme 1) or by Sonogashira (Schemes 4, 5, and 8) cross-coupling reactions. The flat D₃-symmetrical receptors (R,R,R)- 1 and (S,S,S)- 1 formed 1 : 1 cavity inclusion complexes with octyl 1-O-pyranosides in CDCl₃ (300 K) with moderate stability (ΔG⁰ ca. −3 kcal mol⁻¹) as well as moderate diastereo- (Δ(ΔG⁰) up to 0.7 kcal mol⁻¹) and enantioselectivity (Δ(ΔG⁰)=0.4 kcal mol⁻¹) (Table 1). Stoichiometric 1 : 1 complexation by (S,S,S)- 2 and (S,S,S)- 3 could not be investigated by ¹H-NMR binding titrations, due to very strong signal broadening. This broadening of the ¹H-NMR resonances is presumably indicative of higher-order associations, in which the planar macrocycles sandwich the carbohydrate guests. The less planar C₂-symmetrical receptor (S,S,R)- 3 formed stable 1 : 1 complexes with binding free enthalpies of up to ΔG⁰=−5.0 kcal mol⁻¹ (Table 2). With diastereoselectivities up to Δ(ΔG⁰)=1.3 kcal mol⁻¹ and enantioselectivities of Δ(ΔG⁰)=0.9 kcal mol⁻¹, (S,S,R)- 3 is among the most selective artificial carbohydrate receptors known.     

Synthesis of 8-Methoxycarbonyloctylβ-Glycosides of Tri-and Tetrasaccharides Related to Schizophyllan and Neoglycoproteins Therefrom

Abstract

The 8-methoxycarbonyloctyl β-glycosides of the trisaccharides O-β-d-Glcp-(1 → 6)- O-β-d-Glcp-(1 → 3)-d-Glcp and O-β-d-Glcp-(1 → 3)-O-[β-d -Glcp-(1 → 6)]-d-Glcp and of the tetrasaccharide O-β-d-Glcp-(1 → 3)-O-[β-d-Glcp-(1 → 6)]-O-β-d-Glcp-(1 → 3)-d-Glcp, corresponding to the fragments of schizophyllan, have been synthesized by using mono- to tetrasaccharide 1-thioglycosides as glycosyl donors, each bearing a participating benzoyl group in the 2-position, and N-iodosuccinimide and silver triflate as promoter. Saponification of the tri- and tetrasaccharide β-glycosides, followed by attachment to bovine serum albumin of the resulting sugar derivatives having a carboxyl group at the aglycon terminal, provided neoglycoproteins for immunological studies of the polysaccharide.     

Nonlinear viscoelasticity of polystyrene solutions. I. Strain-dependent relaxation modulus

Strain-dependent relaxation moduli G(t,s) were measured for polystyrene solutions in diethyl phthalate with a relaxometer of the cone-and-plate type. Ranges of molecular weight M and concentration c were from 1.23 × 10⁶ to 7.62 × 10⁶ and 0.112 to 0.329 g/cm³. Measurements were performed at various magnitudes of shear s ranging from 0.055 to 27.2. The relaxation modulus G(t,s) always decreased with increasing s and the relative amount of decrease (i.e.,–log[G(t,s)/G(t,0)]) increased as t increased. However, the detailed strain dependences of G(t,s) could be classified into two types according to the M and c of the solution. When cM < 10⁶, the plot of log G(t,s) versus log t varied from a convex curve to an S-shaped curve with increasing s. For solutions of cM > 10⁶, the curves were still convex and S-shaped at very small and large s, respectively, but in a certain range of s (approximately 3 < s < 7) log G(t,s) decreased rapidly at short times and then very slowly; a peculiar inflection and a plateau appeared on the plot of log G(t,s) versus log t. The strain-dependent relaxation spectrum exhibited a trough at times corresponding to the plateau of log G(t,s). The longest relaxation time τ₁(s) and the corresponding relaxation strength G₁(s) were evaluated through the “Procedure X” of Tobolsky and Murakami. The relaxation time τ₁(s) was independent of s for all the solutions studied while G₁(s) decreased with s. The reduced relaxation strength G₁(s)/G₁(0) was a simple function of s (The plot of log G₁(s)/G₁(0) against log s was a convex curve) and was approximately independent of M and c in the range of cM <10⁶. This behavior of G₁(s)/G₁(0) was in agreement with that observed for a polyisobutylene solution and seems to have wide applicability to many polymeric systems. On the other hand, log G₁(s)/G₁(0) as a function of log s decreased in two steps and decreased more rapidly when M or c was higher. It was suggested that in the range of cM < 10⁶, a kind of geometrical factor might be responsible for a large part of the nonlinear behavior, while in the range of cM > 10⁶, some “intrinsic” nonlinearity of the entanglement network system might be important.     

Vibrational spectra of icosahedral (Ih and I) fullerenes

On the bases of the topological structures of the three big classes of icosahedral fullerenes: (1) C_n(I_h, n=60h²; h=1, 2,…), (2) C_n(I_h, n=20h²; h=1, 2,…), and (3) C_n(I, n=20(h²+hk+k²), h>k; h, k=1, 2,…), we derived formulas for the decomposition of their nuclear motions into irreducible representations. Hence, we obtained the infrared and Raman active modes for all of the icosahedral (I_h and I) fullerenes theoretically. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 66 : 113–117, 1998